Laser-Induced Graphene (LIG) as a Smart and Sustainable Material to Restrain Pandemics and Endemics: A Perspective.

A healthy environment is necessary for a human being to survive. The contagious COVID-19 virus has disastrously contaminated the environment, leading to direct or indirect transmission. Therefore, the environment demands adequate prevention and control strategies at the beginning of the viral spread. Laser-induced graphene (LIG) is a three-dimensional carbon-based nanomaterial fabricated in a single step on a wide variety of low-cost to high-quality carbonaceous materials without using any additional chemicals potentially used for antiviral, antibacterial, and sensing applications. LIG has extraordinary properties, including high surface area, electrical and thermal conductivity, environmental-friendliness, easy fabrication, and patterning, making it a sustainable material for controlling SARS-CoV-2 or similar pandemic transmission through different sources. LIG's antiviral, antibacterial, and antibiofouling properties were mainly due to the thermal and electrical properties and texture derived from nanofibers and micropores. This perspective will highlight the conducted research and the future possibilities on LIG for its antimicrobial, antiviral, antibiofouling, and sensing applications. It will also manifest the idea of incorporating this sustainable material into different technologies like air purifiers, antiviral surfaces, wearable sensors, water filters, sludge treatment, and biosensing. It will pave a roadmap to explore this single-step fabrication technique of graphene to deal with pandemics and endemics in the coming future.

Introduction

In today’s world, COVID-19 has caused significant changes to the environment, society, and economy.[1] The emergence of the highly pathogenic virus named SARS-CoV-2 had called a global health emergency, leading to lockdown in many areas worldwide. From December 2019 to December 2021, it has infected around 260 million people, out of which approximately 5 million people have died.[2] The SARS-CoV-2 virus is an enveloped virus with single-stranded RNA belonging to the family Coronaviridae and genus Betacoronavirus, which includes Severe Acute Respiratory Syndrome (SARS) coronavirus, Middle Eastern Respiratory Syndrome (MERS) coronavirus, bat coronavirus, and other SARS-related coronaviruses (SARSr CoV).[3] The glycosylated proteins present on the spikes of the virus bind with the host cell receptor angiotensin-converting enzyme (ACE2), thereby intervening in the virus entry.[3,4] The direct transmission of the virus is through human-to-human contact or via bioaerosol droplets.[5] Due to the direct access of the virus from airborne aerosols, various governments and organizations have mandated surgical masks, gloves, face shields, etc., for safety precautions. However, the viral infection through surface exposure, including door handles, cars, trains, etc., also becomes a major concern when the survivability of the strain remains for 48–72 h.[6]

Additionally, the COVID samples have also been found in the fecal and anal swabs of the patients.[7−9] Furthermore, the fecal bioaerosol transmission of the virus through toilet flushing has also been discovered in various studies.[10,11] The virus strains have been found not only in the air but also in wastewater samples, thus creating a chance for contamination and infection in poor infrastructure areas like slums.[12,13] Sprinkler systems in irrigation could aerosolize the virus, which can contaminate the crops and the fields.[10] Also, the sludge produced from wastewater is used as fertilizers in agricultural fields. The virus contained in the sludge may get deposited on the soil and the crops, leading to contamination in the groundwater supply, as suggested by some studies.[7,14,15] Due to the low temperature inside the ground, the survivability of the virus might increase, which can enhance the chances of infection.[7] Additionally, the risk of consuming contaminated market garden products also becomes high as the virus can survive several days on the garden product.[16] Many treatments have been encountered to kill the virus, including UV, chemical-based disinfectants, metals, etc. However, excessive use of these may lead to mutation.[17] Therefore, plausible materials with antiviral properties can be helpful to stop the spread of SARS-CoV-2.

A graphene-based material has caused a significant revolution in the past 10 years, which has led to noteworthy technological advancements in materials science and related fields.[18−21] Due to extraordinary properties such as high surface area, electrical conductivity, surface-mediated action, easy functionalization, etc., it has unveiled its applications in various biomedical and environmental fields.[19,22,23] Laser-induced graphene, a form of three-dimensional carbon nanomaterial, is prepared by scribing a laser on many carbonaceous precursors in a single step.[21,24] Its facile and straightforward preparation makes it a low-cost material for surface-based applications. LIG has excellent potential for antiviral action due to its excellent electrochemical and surface properties.[25−27] The exceptional surface and antiviral properties of LIG make it an ideal material for the prevention of viral contamination via different ecological routes, including air, water, soil, and surfaces. The easily modifiable texture and surface characteristics help in better attachment of the virus for contact killing action.[28] Different textures such as nanofibers promote specific orientation of attachment, which can lead to effective killing. Moreover, improvising surface characteristics such as hydrophobicity could lead to strong van der Waals interactions of the surface with the phospholipids of the viral membrane. In addition, it has been seen that LIG could be heated up to a temperature greater than ∼200 °C within 5 s at an applied power of 0.53 W/cm2. The time required for cooling LIG up to room temperature is also ∼5 s.[29] This electrically induced heating effect could promote the self-sterilization capability to remove airborne pathogens and surface contamination. The high conductivity of LIG facilitates better electrochemical performance than other metal-based electrodes due to increased electron mobility and low oxygen overpotential.[30] Incorporating these properties in a membrane filter could also give complete inactivation of pathogenic species to prevent transmission through water sources. The high charge storing capacity of LIG and its amicable synthesis provide a large-scale platform for sensing-based applications.[31,32] Additionally, high nucleobase adsorption potential makes it an active surface for specific recognition capability.[33] Apart from this, LIG holds great potential for new-generation sustainable materials because of its low-cost preparation and environmental safety.

A sustainable material should positively impact the communities and the environment for developing the product and delivering services. The most significant aspect of material sustainability lies behind choosing a resource-efficient process along with balancing several factors.[34] The factors include fabrication process, energy demand, environmental impacts, resource consumption, economics, quality efficiency, etc.[35] According to the United States Environmental Protection Agency (USEPA), global raw material usage has increased twice the population growth rate.[36] For every 1% increase in products, the raw materials rise by 0.4%, which comes at a high cost to the environment, including biodiversity loss and higher greenhouse gas emissions (GHGs).[37,38] Even around 42% of total GHGs are being generated from material management only.[39] Therefore, adopting sustainable materials followed by adequate control becomes essential, failing to which will lead to grave implications on the economy, environment, and society. In the case of nanomaterials, a tremendous amount of risk is being posed during handling and exposure due to their chemically intensive preparation. From the past decade, the adoption of green chemistry has been increased widely for material synthesis. Green chemistry is “the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture, and application of chemical products”.[40,41] Thus, its integration into the synthesis methodology is significant for risk reduction and its early development and wide acceptance. This article aims to pave different approaches to prevent COVID-19 or similar pandemics by using a sustainable material, i.e., “laser-induced graphene (LIG)” to detect, diagnose, and kill the viral strains from contaminated surfaces. Apart from that, a glimpse of LIG’s antiviral and antibacterial properties will be described for better understanding. The possibility of it in control and preventive technology in various applications, including air and water purification, trace-contaminant or viral load detection, antimicrobial surface preparation, monitoring, and sensing-based applications, has been shown here. These engrossing properties of LIG will provide a perspective to the scientific community to expedite more research on this material.

Laser-Induced Graphene: A Novel and Sustainable Way to Synthesize Graphene

Graphene, a widely used material in numerous technologies, is majorly prepared from a chemical reduction route called “Hummer’s method”.[42,43] The baseline material for synthesis includes graphite, which could be either mined or synthesized. However, due to the lower cost of mining, mined graphite is usually taken as the raw material. After that, the graphite is oxidized to graphene oxide before conversion to graphene. In this method, potassium permanganate, sulfuric acid, sodium nitrate, and phosphoric acid are used, followed by hydrogen peroxide to neutralize the excess of permanganate. According to Arvidsson et al., acid and solvent recovery in such methods is an issue that requires extensive energy and operational cost.[44] Additionally, the release of toxic fumes of N2O4 and NO2 in the air and the leaching of ions in water again become an environmental concern.[45] Apart from chemically assisted treatment, many scientists have started adopting greener practices, including ultrasonication and microwave-assisted technologies; however, significant disadvantages lie in producing lower yields and only a few-layered graphene.[46]

Moreover, for surface-based graphene, the chemical vapor deposition (CVD) method is widely used to form thin films.[47,48] It involves thermally induced chemical reactions on the surface of the substrate, with reagents being supplied in the form of gases such as hydrogen and methane. However, considering the energy requirements for methane, the cost of operation, and long-term feasibility, the method does not prove to be a sustainable solution.[49] Furthermore, surface-based coating techniques like dip coating, drop-casting, Langmuir–Blodgett method, and electrophoretic deposition have also been explored; nonetheless, they require precise control over the orientation of the films, which is challenging during bulk production.[50]

Besides these techniques, laser scribing is an attractive yet sustainable technique for the current era. The method proves to be resource-efficient as it does not need any specific raw material, and any carbonaceous surface would act as a great substrate.[24] Even the biomass, including potato, bread, coconut, cotton cloth, and minuscule waste, has been converted into graphene via this technique (Figure c–h).[24,51] Compared to the other approaches, laser-induced graphene preparation is a single-step green synthesis. LIG fabrication is instantaneous and proves to be environmentally benign as it does not require any chemical treatment, bringing off a lot of energy and time in recovering disposed chemicals or solvents. The control on the size, texture, and multilayer graphene formation is a challenge in graphene production, for which additional steps like tape peeling methods or ultrasonication have been incorporated in some studies.[52−54]

Figure 1

(a) Schematic showing excellent properties of laser-induced graphene (LIG). (b) Defocusing increases the spot size of the laser, resulting in overlapping and multiple exposures, while at the focal plane, non-overlapping spots are produced. (c) LIG made on bread in the form of the alphabet “R”. (d) LIG made on pinewood in the shape of an owl. (e) LIG made on cotton paper in the shape of an owl. (f) LIG made on muslin cloth in the shape of an owl. (g) LIG made on muslin cloth in the shape of an owl wrapped around a marker. (h) LIG formed on a piece of cardboard. (b–h) Reprinted (adapted) with permission from ref (24). Copyright 2018 American Chemical Society.

On the contrary, by using an appropriate laser setting, graphene size, morphology, and texture can be easily controlled without any additional step. Lasers ranging from infrared, ultraviolet,[55] and visible ranges[56,57] have been employed for the synthesis of LIG. Although LIG has been first prepared on a PI sheet via an infrared CO2 laser,[58] later, many studies have explored the potential of different lasers, intending to improve the spatial resolution of LIG.[59] This method also provides an excellent platform for fabricating different graphene morphologies via variation in operational modes of laser-like pulse density, laser duty cycle, focus and defocus, etc. The defocusing mode increases the laser spot size, which results in more overlap, thereby causing multiple exposures to the surface (Figure b).[24] The morphologies obtained until now include fibers, sheets, droplets, and spherical and tubular structures.[60−62] The morphic transitions lead to manipulation in graphene properties, which helps in application-specific optimization. For example, the change in hydrophobic characteristics or surface tension will change adherence properties, as shown by Ye et al.[63]

Laser-induced graphene is a three-dimensional form of graphene consisting of multiple layers. Its specialty arises from its single-step, cost-effective preparation to the versatility among many carbon precursors.[64] The controllable fabrication, design, and texture of the material via computer-based systems hold a great promise toward printable electronics for sensing-based applications. Due to its highly conductive and mechanically robust nature, it has been applied as a catalyst for hydrogen peroxide generation and water splitting reactions.[65,66] Compared to other materials, a very low oxygen overpotential could be achieved at minimal voltage, making it an appealing tool in electrochemical applications.[65] The inculcation of inert gases like argon or hydrogen during graphene preparation helps in tuning the surface properties of LIG from superhydrophobic to superhydrophilic.[67] These properties facilitate the attachment or detachment of external stimuli over the surface, which is also one of the primary reasons for its antibiofouling nature. In addition to this, LIG can be integrated with certain host materials such as metals or metal oxides, additives, or heteroatoms to form composite materials. Even embedded materials could be fabricated by transferring LIG through infiltration onto a different substrate.[64]Figure a shows a summary of LIG’s properties that are useful for electrochemical, antimicrobial, and sensing-based activities. Despite this, laser-incorporated methods such as laser-reduced graphene (LRG) and laser-reduced graphene oxide have also been explored.[68,69] However, these methods conserve all the advantages, such as robustness, mechanical strength, selective localized reduction, flexibility, and pattering. Furthermore, the fascinating property of LIG lies behind it, leaving minimum to no toxic imprint on the environment, thus making it sustainable to use in the current situation. The antiviral, electrochemical, and photothermal properties of LIG are discussed here, which will pave the way for the scientific community to conduct more research and simultaneously promote sustainable material for future implications.

Antimicrobial and Antiviral Action of Laser-Induced Graphene

Effect of Surface Properties and Texture

The antimicrobial property of LIG arises from its hydrophilic nature and texture, which inhibits microbial attachment on the surface with simultaneous killing action. Due to the negatively charged surface of LIG, foulants and microbes with similar charges do not adhere to its surface.[25] Laser parameters could be varied to get the desired texture and surface properties for effective killing. Singh et al. produced nanofibers and nanoporous structures that resulted in sharp edges similar to graphene. Such a type of texture promotes lower adhesion energy between the microbe and the contact surface, thereby preventing biofouling phenomena.[70] This type of property is quite attractive for antiviral action against SARS-CoV-2 without using any external agent like heat or toxic chemicals. The virion envelope of the SARS-CoV-2 virus could be cleaved, leading to the release of glycoproteins.[71] The oxidized LIG powders have shown properties similar to GO with an improved antibacterial activity, as shown by Singh et al. and Liu et al.[25,72] However, it can be enhanced by incorporating antimicrobial agents such as silver.[73] An interpretation of this action has been conducted on Pseudorabies and Porcine epidemic diarrhea virus (PEDV).[74] PEDV is an alphacoronavirus that infects neonatal pigs with acute diarrhea, vomiting, and dehydration.[75] The virus deactivation was shown by the insertion of graphene, leading to the destruction of glycoproteins in the virion envelope.

Singh and co-workers prepared antimicrobial LIG powders by scribing the PI-LIG surface, followed by sonication.[25] The antimicrobial activity of the powders was evaluated both in bulk solutions and on the surface.[25] The graphene powder with a smaller size (0.09 μm2) has shown an increased killing effect compared to that with a larger size (0.55 μm2) due to the presence of a small edge feature in graphene. The enhanced effect of the antimicrobial property could be examined via doping of oxidizing agents, metal-active compounds, heteroatoms, etc. The powders were then oxidized via KMnO4, which enhanced the antibacterial activity by 40% (Figure a). The oxidative stress mechanism gets amplified on account of higher oxygen content.[76] For the viral proteins, this might cause lipid peroxidation to the cells.[77,78] However, the lasing parameters and synthesis atmosphere might affect LIG’s morphology and oxygen content.

Figure 2

(a) Bacterial % inhibition comparison between the PI film, LIG, the cellulose membrane, large LIG powders, small LIG powders, and oxidized LIG powders. (b) Comparison between the PI film, LIG, the cellulose membrane, large LIG powders, small LIG powders, and oxidized LIG powders. (c) Schematic showing the antifouling property of LIG and crushed LIG with the IMARIS software image of biofilm growth (red color, dead cells; green color, live cells). (d) Schematic showing Ag-doped LIG antimicrobial action via contact as well as ion release killing (adopted and modified).[73] (a, b) Reprinted (adapted) with permission from ref (25). Copyright 2017 American Chemical Society. (c) Reprinted (adapted) with permission from ref (70). Copyright 2018 American Chemical Society.

Surface chemistry also plays a significant role in determining the attachment of the virus to the LIG surface. The bacterial or viral envelope could be attached to graphene via strong π–π interactions,[6] which would further be assisted by the surface charge on the material. Thus, due to the highly negative surface charge of graphite (zeta potential = −117 mV), which is very high compared to LIG (−44.4 mV), it has shown an increased growth rate of biofilms as compared to LIG and PI (zeta potential = −76.1 mV) films (Figure b).[25,70] The texture of LIG also matters in such a case, which was shown via an extended work by Singh et al.[70] The microporous and nanofibrous texture shows high biofilm inhibition due to the weaker adhesion energy as compared to flat crushed LIG (Figure c). This property can help prevent COVID-19 virus attachment to surfaces where it stays up to 3 to 4 days.[79] LIG’s property could also be broadened by inducing superhydrophobicity and superhydrophilicity on the surfaces.[64] Under different gaseous environments such as Ar and H2, LIG’s surface could turn out as superhydrophobic (contact angle = 180°); on the contrary, an oxygenated environment can produce LIG with superhydrophilic (contact angle = 0°) surfaces. Therefore, based on the treatment action, surfaces can be modified. For example, a disinfectant attachment with the virus could be enhanced by making superhydrophobic surfaces, or the biofilm formation or surface attachment could be minimized by using superhydrophilic surfaces.[64]

The antiviral or antimicrobial property could be escalated by doping metal active agents,[80−82] resulting in even stronger electrostatic bonding through intercalation.[42−44] Silver-doped LIG has shown enhanced antibacterial and antiviral activity through the active surface property of graphene and silver leaching (Figure d). Pseudomonas aeruginosa was tested against silver-doped LIG sheets with a 99.9% killing effect, which is suggested to be due to the cooperative effect caused by silver ion leaching.[73] Recently, coronavirus strains HCoV-OC43 and HCoV-229E were tested against Ag-NP-incorporated LIG, and a killing of around 99% of the cells had occured within 15 min.[83] The AgNO3 solution was poured on the polyimide sheet, followed by laser scribing. Size reduction phenomena occurred along with graphitization, which reduced the size of silver particles to silver nanoparticles. However, extensive application of silver or other chemicals might lead to virus mutation.[17] Therefore, to limit the cytotoxicity issues, the controlled release of chemical-based disinfectants should be promoted. Doping procedures could opt for capping agents and stabilizers to prevent the excessive release of these materials in the environment. LIG could also be incorporated with some antimicrobial agents like antibiotics, disinfectants, nanoparticles, and antimicrobial polymers to strengthen and intensify disinfection performance.

Joule Heating Effect

Joule heating is a conventional way to sterilize and pasteurize food products. Many different materials ranging from polymers,[84] nanotubes,[85,86] minerals,[87] metals,[88,89] etc., have been utilized to analyze heat transfer phenomena and sterilization. The sterilization principle lies behind converting an electric current into heat as it passes through a resistance, which leads to the thermal inactivation of microbes. LIG materials can act as pliable heaters and produce temperatures of up to 300–1400 °C,[90] which is far above for microbial sterilization and decomposition of nocuous materials such as endotoxins.[29] Endotoxins are heat-stable lipopolysaccharides, which can cause the proliferation of the cells even after inactivation.[91] The technique proves to be essential in the present time, where cytotoxicity issues are becoming an extensive pitfall for long-term disinfection applications. The tolerable conductivity of laser-induced graphene, i.e., a sheet resistance of 5–20 ohm, enables it to be joule-heated by electrical power dissipation. Considering this, LIG has been investigated as self-sterilizing with a property to capture and kill microbes.[29] Joule heating requires low energy and economic inputs, making it an attractive alternative for disinfection and sterilization applications in the context of the current need.

The expansion of LIG from hydrophilic to hydrophobic could be helpful in processes like oil–water separation, biosensing, and heat transfer application.[92] However, in the context of microbiology, it would instead facilitate better attachment of microbes with the material’s surface due to strong hydrophobic interactions, including van der Waals interaction and π–π stacking.[93] A study by Huang et al. has demonstrated the antiviral properties of hydrophobic LIG (HLIG) and compared it with hydrophilic and Ag-NP-incorporated LIG.[83] Hydrophobic LIG produced under inert conditions has shown more than 95% killing of HCoV-OC43 and HCoV-229E. HCoV is a human coronavirus that infects humans and mammals.[94] This virus is enveloped and consists of single-stranded RNA, which almost resembles the property of SARS-CoV-2. The LIG composite was tested under mild conditions (∼46 °C), and within 15 min of exposure to sunlight, it was able to kill 95% of the viable MRC-5 cells (Figure a,b,d,e), which can also be seen in the immunofluorescence images (Figure c). The temperature soared up to 55 °C in 10 s when exposed to 1 kW m–2. Compared to LIG and Ag-NPs/LIG with HLIG, HLIG was found to have maximum antiviral property compared to the former two (Figure a,b,d,e). The hydrophobic nature of HLIG could promote interaction between the viral envelope and graphene, which led to the destruction of the lipid membrane, thereby weakening the virus under photothermal conditions.[83]

Figure 3

(a) Antiviral effect of LIG, HLIG, Ag-NPs/LIG, and MBF on HCoV-OC43. (b) Antiviral effect of LIG, HLIG, Ag-NPs/LIG, and MBF on HCoV-229E. (c) Immunofluorescence images of MRC-5 cells after being infected with virus (red color representing viable cells). (d) Antiviral activity against HCoV-OC43 with and without light. (e) Antiviral activity against HCoV-OC43. Reprinted with permission from ref (83). Copyright 2021 John Wiley and Sons.

Moreover, the method has also been employed in air filters to remove pathogenic species with the simultaneous effect of self-sterilization. A group from Rice University has tested LIG filters made from the polyimide film (PI) for air filtration,[29] which were able to capture the particulate matter and bacteria on the application of electricity and pressure (Figure a). Due to LIG’s low heat capacity, it can reach a temperature of up to 380 °C (Figure b) within seconds, with minimal power consumption. The self-sterilization property has also been shown in nonwoven LIG air filters fabricated by Gupta et al.[95] This property is quite appealing for the faster inactivation of microbial species with less input energy. However, a range of filters are available in the market, like HEPA or ULPA filters composed of borosilicate fibers, but the overall economics and energy inputs are substantial enough to utilize these in low-income areas such as villages or slums where viral breakdown could occur spontaneously. Different studies have elucidated the presence of viral load in the air up to 1.8–3.4 viral RNA copies per liter of air,[96] signifying the need for indoor air treatment to prevent transmission at the beginning stage.[96] LIG filters have proven to be a versatile solution for easy material preparation, low energy consumption, and minimal operational inputs. However, research should shift toward evaluating their scalability for point-of-use (POU) potable filtration units.

Figure 4

(a) Schematic of filtration assembly with joule-heated LIG filters on the PI film, backed with PES filter and connected to a vacuum pump. (b) Schematic showing the joule heating phenomena on exposure to applied voltage along with an infrared image of the LIG filter, joule-heated up to 380 °C (dotted lines show the LIG surface area). (c) Schematic showing LIG-based antibacterial masks. (d) Temperature profile of LIG, activated carbon fiber (AC), and melt-blown fabric (MBF). (e) % Antibacterial efficiency comparison between LIG, AC, and MBF over the time course of 1, 5, and 10 min, respectively. (a, b) Reprinted (adapted) with permission from ref (29). Copyright 2019 American Chemical Society. (d, e) Reprinted with permission from ref (97). Copyright 2020 American Chemical Society.

The concept of joule heating was also envisioned in face masks, and Huang et al. have reported photothermally enhanced bacteria killing on a LIG-based face mask (Figure c).[97] The bacterium Escherichia coli was taken as a surrogate for SARS-CoV-2 as both cannot sustain temperatures beyond 60 °C.[98,99] The bacterial viability on the surface of masks remains for 8 h, which enhances the risk of getting spread during their removal or improper disposal. The study evaluated the loss of bacterial viability on the LIG surface compared to commercially available activated charcoal and melt-blown fabric face masks. The nanofibrous surface of LIG has prevented bacterial proliferation along with bactericidal effects caused by the sharp edges of graphene.[70] The enhanced killing effect was accessed upon subjection to sunlight, which resulted in a 90.5% capturing rate of bioaerosols. Due to the excellent broadband absorption of LIG, as evidenced by the temperature profile of LIG (Figure d),[100] the photothermal effect enhanced the bactericidal property of LIG up to 99.99% after a 10 min exposure to sunlight, as shown in Figure e. Joule heating has proved to be a promising technique for point-of-use disinfection treatment. The development of LIG-based joule heaters would help remove pathogens and generate self-sterilizing conditions, which otherwise would not be achieved with other materials owing to high cost and energetics.[101,102]

Electrochemical Disinfection

Electrochemical disinfection has gained popularity since the 19th century due to its unique combination of electricity and chemical oxidants.[103] Several electrode materials have been employed for the application; however, comparatively high current densities and voltages are required to achieve the aimed performance.[101] Over the past years, laser-induced graphene has shown extraordinary electrical performances due to its high charge density and electron mobility, making it promising for electrochemical applications.[25,65,66] The increased surface provides better contact of the oxidants to the microbial species. The exposure to different voltages ranging from 2.5 to 20 V has shown both antiviral and antibacterial properties, leading to complete inactivation of the cells (Figure b). Barbhuiya et al. have investigated 100% inactivation of Vaccinia virus through an electrochemical LIG membrane-based disinfection technique at 20 V in water.[104] The virions were killed by an amalgamation of both chemical and electrical effects. Oxidants including hydrogen peroxide and chlorine have been generated, which could facilitate oxidative stress in the species. Additionally, the electrical effects caused the negatively charged bacterial membrane to be damaged at the contrasting positively charged anode (Figure a).[25]

Figure 5

(a) Schematic showing the mechanism of bacterial and virus inactivation through electroconductive LIG membranes (adopted and modified).[104] (b) Bacterial and viral inactivation at different voltages at 1000 m–2 h–1 via LIG filters.[104] (c) P. aeruginosa removal at low voltages via PES LIG filters at an initial concentration of ∼106 CFU/mL and a flow rate of ∼500 L m–2 h–1. Reprinted (adapted) with permission from ref (66). Copyright 2018 American Chemical Society.

Singh et al. have extrapolated this technique to flow-through vacuum filtration with stacked LIG membranes, wherein at a flux of 500 L m–2 h–1 and a voltage of 2.5 V, complete log reduction and inactivation of P. aeruginosa were investigated, as shown in Figure c.[66] Even at a voltage of 20 V, mixed consortia of microbes in a wastewater sample were inactivated at ultrahigh flow rates.[66] The detection of SARS-CoV-2 in wastewater has not been identified yet as a potential transmission source; however, studies correlate the plausible infection with the amount of RNA found in the water samples.[12] This encourages the analysis at the national and international levels to do the water epidemiological studies.[105] Furthermore, the virus characteristics and survivability in water fluctuate with environmental conditions,[7] thereby urging a robust disinfection system. According to Venugopal et al., the capacity of nanocomposite membranes to capture the high-risk pathogen is outstanding,[13] and nanocomposite LIG membranes could be a versatile alternative for capturing SARS-CoV-2. The electroconductive LIG membrane on application of electricity would kill the species on account of the above-described mechanism.[26] However, more research on LIG with different surrogates of enteric viruses should be conducted, which would help in better surveillance of the viral transmission and exploration of water epidemiological studies via the genetic materials obtained in the sample.

Membrane filtration processes, such as ultrafiltration, nanofiltration, and reverse osmosis processes, can remove pathogens, including bacteria, viruses, fungi, cysts, etc.[106−108] Laser-induced graphene ultrafiltration membranes have been fabricated for antibiofouling and antimicrobial action. The electrically conductive filters were coated with a graphene oxide (GO) layer to make them robust to sustain high flux treatment.[27] With the increased crosslinking of GO, the bovine serum albumin (BSA) rejection was increased by 70%. Also, the biofilm growth was typically reduced by 83% compared to traditional polymeric UF membranes, which is believed to be because of its 3D texture and nanofibers.[70] The antimicrobial activity was tested in the presence of electricity with a flux of 100 L m–2 h–1 and on the application of 2 and 1.5 V, respectively; 6 log reduction and 3 log reduction were achieved. However, for viruses, a bit higher voltage may be required, as suggested by Barbhuiya et al.[26] Another similar study was done by Gupta et al. wherein PVA was adopted as a crosslinking agent with the prospect of improving the scalability of LIG composite membranes.[109] The membranes were able to remove up to 25% of BOD and COD with around 900–1300 L m–2 h–1 bar–1 pure water permeability (PWP). Also, on the application of low voltages, the complete exclusion of P. aeruginosa has occurred. The role of crosslinkers and coating agents thus becomes vital for a long-term application. The compatibility of different polymers to form LIG with roll-to-roll processing[110] and laminated surfaces[51] shows promising early commercial applications[111] of membrane-based water technology.

LIG as a Biosensor for the Detection of SARS-CoV-2

Due to the community spread of coronavirus and high morbidity statistics, its fast detection becomes pivotal before the viral breakdown in areas with high population densities. Therefore, the development of rapid detection kits has put forth an unprecedented urge. However, they come with plenty of errors, thus creating an increased chance for a false-negative report. RT-PCR tests are reliable in such cases with nucleic acid detection assays.[112] Still, they consume a lot of time due to the PCR amplification process. This technique is quantitatively used to detect RNA virus infections such as HIV, SARS-CoV-2, and hepatitis C virus.[113] Biosensors, in such cases, act as an appealing option with an intelligent specific recognition of the target and sensitive readout of the signals.[114] This technology helps in the rapid, facile, and cost-effective detection of SARS-CoV or similar outbreaks and the efficient allocation of healthcare and medical resources.

The intervention of nanotechnology has produced a range of nanomaterial-based biosensors,[18,33,115] including metal NPs, carbon-based nanomaterials,[116,117] polymeric nanomaterials, etc. Carbon-based nanomaterials, especially graphene, are captivating due to their unique physicochemical properties and biocompatibility. The strong interaction of biomolecules with specific recognition capability makes them promising for constructing stable and sensitive sensors for pathogen detection.[118,119] Methods like chemical vapor deposition (CVD),[120] oxidation–reduction,[121] and mechanical exfoliation[122] have been used for graphene preparation. However, multiple pitfalls arise, including high cost, chemical intensification, and low commercialization, increasing the scientific community’s focus on developing novel and facile methodologies. Compared to other multistep fabrication methodologies, LIG synthesis is a one-step fabrication that generates several corrugations and defect densities, enhancing electron transfer kinetics at the basal edges of graphene.[123] Moreover, the 3D porous aromatic network can improve charge transfer efficiency and mass transport because of its high conductivity and specific area, which are crucial for biosensing. Also, compared to other graphene-based sensors, LIG sensors hold a greater capacity for industrial commercialization, as manifested by Kaner and El-Kady, in which 100 devices of graphene were prepared by laser scribing within less than 30 min.[124]

A range of sensors have been developed using LIG for electrochemical nitrogen sensing,[31] sound sensing,[56] gas sensing,[125] salinity testing,[126] dopamine sensing,[127] and bisphenol A sensing.[128] In addition, biosensing applications of LIG have been explored to detect biogenic amines,[32] antibiotics,[117] aptamer,[128] glucose,[116] and urea.[129] The material’s biocompatibility could be increased by either introducing metal active agents[130] or covalent interactions via DNA or antibody attachment on the surface.[131,132] Pathogenic species such as viruses and bacteria can be detected by recognizing nucleic acids, peptides, aptamers, and antibodies. However, antibody identification is precise, with strong recognition potential along with real-time monitoring. Graphene-based materials have shown their potential for sensing all three types of units.[133] The nucleic acid detection of miRNA has been found to be an estimable technique for low concentrations of samples, which helps in early detection of virus before its incubation.[134−136] In the recent years, graphene-based materials have been an attractive alternative in the field of electrochemical biosensing. It has been shown that the material has a high tendency to adsorb nucleobases via physisorption mechanism, altered by the polarizability of the substrate.[137−139] Accurate detection of adsorption of genomic entities like DNA or RNA biomarkers could considerably reduce the cumbersome chemical routes used to fabricate sensors.[140−142] This also helps in simplifying the detection methods over conventional recognition and transduction approaches.

Wan et al. combined the nucleobase adsorption with the magnetic isolation and purification technique.[123] LIG electrodes were fabricated on the PI film, which served as a nitrogen-doped substrate, leading to enhanced conductivity and sensitivity to nucleic acids.[123] The preeclampsia-specific miRNA hsa-miR-486-5p was explicitly adsorbed on the surface of the LIG electrode. Differential pulse voltammetry (DPV) in the presence of a ferric cyanide complex was used to detect the miRNA. The sensors produced were susceptible to responding to femtomolar concentrations with a high rate of reproducibility. The electrochemical recognition capability could be enhanced by using antibody and antigen interactions. At the same time, the signals detected could be obtained by the use of either nanoparticles or redox-active species.

Recently, a similar technique was investigated in the detection of SARS-CoV-2 by Gao et al., in which a wireless multiplex potable immunosensor was fabricated (Figure a). The sensor could detect biomarkers of COVID-19 in both blood and saliva, as shown in Figure .[143] Nucleocapsid proteins, immunoglobins, and inflammatory biomarkers against the virus spikes were detected in a physiologically relevant range. 1-Pyrenebutyric acid was used as a crosslinker to anchor the antibodies on the surface of laser-scribed graphene (LSG) or LIG via π–π stacking (Figure b). The attachment of the antigen assembly and antigen detection were characterized with the help of differential pulse voltammetry (DPV) and open-circuit electrochemical impedance spectroscopy. Four LSG electrodes, graphene counter electrodes, and Ag/AgCl reference electrodes were employed for this. By incubating sensing biomarkers including targeted proteins (CRP and NP) and specific immunoglobins (IgG and IgM) on the surface, the amperometric signals and signal-to-blank (S/B) ratios were quantified (Figure c,d), which were further verified by phosphate buffer solution samples. This technique showed excellent reliability and effectiveness with regard to the current situation. The electrochemical process could also be extrapolated to environmental samples such as soil, as investigated by Garland et al.[31] In addition to this, people have started exploring field-effect transistors (FETs) for the detection of COVID-19 protein spikes.[144,145] Cui et al. fabricated a LIG-based FET via multiple degrees of laser reduction, which formed oyster reef-like graphene channels. A liquid ion gate FET was formed, which modulated the carrier concentration of antibodies in the channel. The LIG-FET has shown high sensitivity with detection limits of up to 1 pg/mL, which are quite high as compared to previously made graphene-based FETs.[144]

Figure 6

(a) Wireless LSG-based electrochemical sensing platform for the detection of SARS-CoV-2 from blood and saliva. (b) Covalent attachment of biomarkers on graphene and the polyimide (PI) surface for the detection of the target SARS-CoV-2 analyte. (c) Amperometric responses and signal-to-blank ratio comparison for SARS-CoV-2 antibody IgG and C-reactive protein (CRP) detection. (d) Amperometric responses and signal-to-blank ratio data for biomarkers, i.e., C-reactive protein (CRP), nucleocapsid protein (NP), and antibodies IgG and IgM. (a–d) Reprinted (adapted) with permission from ref (143). Copyright 2020 Elsevier B.V.

Along with electrochemical sensing, the optical sensing property could also be explored via photoluminescence. The nucleic acid could be incorporated with fluorescent dyes that can be quenched by graphene via nucleic acid adsorption to the surface.[146] However, fluorescence can be restored by nucleic acid hybridization or specific proteins.[114] Photoactive agents like Zn/ZnO could be coated on the LIG surface,[147] which can be designed based on signal fluorescence.[148] The usage of photopolymers could minimize the doping step with the substrate. Beckham et al. have prepared LIG from a photoresist material with a spatial resolution of 10 μm, which is 15 times smaller than the traditional method-prepared LIG.[149] Such patterning methods could fabricate LIG composites for on-chip devices and wearable sensor applications that could be utilized to detect airborne viral genomes.

Challenges and Future Opportunities

The future opportunities of LIG are manifolds in several areas of science and technologies, such as electronics, biomedical, remediation, detection, sensing, and filtration. Various physicochemical processes have been used in the fabrication of graphene to explore its exceptional properties, but the single-step laser scribing technique has recently attracted many scientists and researchers to examine a range of possibilities offered by the material. The single-step fabrication and resource-efficient nature of LIG make it a low-cost material that is prominent for preventing overexploitation of resources. The use of minuscule waste and biomass as the carbon substrate during synthesis simultaneously solves the waste disposal and efficient recycling problem, thus creating a sustainable footprint. LIG could serve a range of opportunities extending from air purifiers and sludge treatment to viral diagnosis and detection. Early detection and diagnosis of microbial infections are indispensable to prevent the plausible spreading. A variety of possible applications of LIG are summarized in Figure for controlling COVID-19 and similar pandemics and endemics.

Figure 7

Schematic showing possible future applications of laser-induced graphene (LIG) for controlling COVID-19 and similar pandemics and endemics.

The airborne transmission of the virus is threatening, which enhances extraordinary precautions at poorly ventilated areas. Due to the photothermal action of LIG, LIG-based air filters could be employed in crowded places such as schools, offices, houses, etc. The microporous LIG filter permits simultaneous removal of contaminants along with disinfection treatment.[29] Different morphologies and textures of LIG could be explored to check the efficacy of microbial adhesion. In addition, the integration of LIG-based airborne sensors with a smartphone-based app could also help in microquality climate control.[150] This will also help in monitoring indoor air transmission and improving the healthcare systems.[150] The minimum efficiency reporting value (MERV) of a single LIG filter bank is reported as approximately 15–16, which is in good agreement with standards given by ANSI/ASHRAE/ASHE Standard 170-2017: Ventilation of Health Care Facilities.[29] This manifests the robustness of a single LIG filter over other double-layered HEPA filters. However, to be used as a substitute to traditional double-layered HEPA filters, the thickness of the polymer must be high to match the efficiency.[29] The low heat capacity of LIG promotes heating in minimal time with a simultaneously fast cooling rate, which makes it an energy-efficient material. This property could be utilized in antiviral surfaces for door handles, mobile covers, or screen guards with a principle of light-induced heating. To prevent abrasion, LIG-sandwiched laminated surfaces could be prepared by using thermoplastic polymers. These polymers help in maintaining the in-plane conductivity while simultaneously providing insulating surfaces.[51] LIG doped with a host material or composites could be applied on face masks.[64,151,152] The cloth of choice for LIG deposition needs to be able to maintain good conductivity and flexibility. Additionally, the usability of the mask depends upon better contact of LIG with the surface and also on less change in resistance during bending or folding. This can be solved by using conductive adhesives or conductive cloth, like carbon cloth, which improves the electrical contact of LIG. Similar arrangements need to be made while preparing PPE kits. Besides this, the toxicity assessment of LIG and its adopted concentration needs to be analyzed well before usage. d’Amora et al. evaluated the toxicity of LIG on zebrafish and found it to be nontoxic even at higher concentrations.[153] Wang et al. and Puetz et al. also set good examples of LIG’s biocompatibility on human breast cells (MDA-MB-231)[154] and epithelial cell line Madnin-Darby Canine Kidney (MDCK-II),[155] respectively. In addition, it is found to be less harmful than other graphene-based nanomaterials, which makes it biocompatible enough to be explored in biological applications.[153]

The LIG water filters could be employed in point-of-use water treatment to control the possible transmission of the virus through drinking water during recreational activities like traveling or trekking. The wastewater treatment technology could incorporate LIG-based nanofibrous membranes in reactors to control the biofouling phenomena and sludge treatment. This would help prevent viral contamination in agriculture through sludge disposal and ultimately in the food products. The chlorine disinfection at water treatment plants has shown promising results against the virus; however, during the lockdown, excessive chlorine concentration has reached household tap water, which led to eye and skin irritation.[156] These phenomena solicit the need for an environmentally benign and long-lasting disinfection system. Despite its fascinating future applications, a handful of challenges also come along the pathway. The major challenge lies in controlling the shelf-life of the membranes. The powdered surface of the membrane needs to be maintained in a robust condition for extrapolating into the applications. For this, a proper selection of crosslinking agents and coating agents needs to be done. This would also help in stabilizing the surface structure during high flux applications. Another challenge is the optimization of the texture, upon which the non-electric antimicrobial action is dependent. Multiple sets of hits and trails would be required for optimal settings of laser to upgrade the texture.

Apart from this, the stability of electrodes, especially the anode, is essential for continuous disinfection applications. The anodic part of the carbon-based electrodes is prone to oxidation and breakdown due to the generation of hydrogen peroxide or similar reactive oxygen species (ROS). Therefore, attempts should be made to increase its resistance by up to anodic potentials. For enhancing the anodic stability, many studies have suggested the anchoring of metal-based nanomaterials as coating agents.[157,158] In contrast, others demonstrated the use of conductive polymers like polyaniline (PANI).[159] Recently, LIG has widely attracted the field of bioelectronics and soft robotics.[154,160] Due to its thermal and bioresponsive nature, LIG could be utilized in making bioresponsive soft robots for biofilm eradication.[161] Hwang et al. examined the role of magnetic nanoparticle-driven antimicrobial soft robotics in damaging the deleterious compounds of biofilm extracellular polymeric substance (EPS).[162] The iron nanoparticles embedded in soft robots performed bactericidal action by generating free radicals, oxidizing the EPS matrix, and magnetic removal of the adhered by-products. 3D modeling and vane-shaped robots have also been fabricated to cover the cylindrical- and helical-shaped areas. Nanoparticle-doped photothermally induced LIG-based actuators could be modeled for similar applications. This would promote an energy-efficient method and help reduce the aging of membranes via chemical treatment.

The role of early sensing and diagnosis is crucial in dealing with any pandemic. LIG, due to its exceptional properties, has shown great potential in sensing-based applications. For COVID prevention technology, LIG biosensors could be fabricated for rapid testing and diagnosis as done by Gao et al. for blood and saliva detection with immunosensor technology.[143] In healthcare facilities, miniaturized wearable temperature monitoring sensors could be equipped with daily testing facilities. In response to temperature variation, thermal vibrations and electron–phonon vibrational features in LIG could be adopted for such applications.[163] Yang et al. prepared a LIG sensor on a PI sheet via vector mode. This resulted in a temperature sensitivity of −0.06% °C–1 and detection limits of up to 0.051 °C, and thus being used for skin temperature detection.[163] Similarly, a LIG-based on-skin hydration wearable sensor could access skin hydration levels, detecting skin impedances.[164] This would be helpful in areas for evaluating skin diseases such as eczema. Along with this, mental stress conditions and cosmetic evaluation can also be assessed.[165]

In addition, LIG-based electrochemical sensors could be equipped with a real-time monitoring tool for environmental systems. The sensors could be integrated with the water treatment plant to monitor the viral load on the treatment sites. Wearable on-site integrated miniature devices should be produced for the quality control sector to monitor soil and crop quality. Due to LIG’s high thermal, mechanical, and light stability along with efficient biocompatibility, biomimetic LIG-based actuators could be fabricated. In such actuators, temperature, light, pH, and electric stimuli can be provided to work by harnessing energy[166,167] and performing bioresponsive tasks. Magnetically responsive actuators could be made by doping appropriate ferromagnetic particles such as cobalt or iron with LIG. The flexible, patternable, and shape-controlling features of LIG provide an immense platform for printable electronics and custom-varied morphologies. Due to the easy roll-to-roll fabrication and lamination, its commercialization aspects in the sensor-based industry are significantly high.[51,64] However, strong bonding between the LIG layer and the substrate remains a constraint. To overcome this, functionalization with viscous polymers like elastomer while transferring LIG onto composites should be performed for better strength and flexibility.[168]

Commercialization Aspects of LIG

The commercialization of LIG holds great promise to the communities due to its economic viability and low energy consumption. Since economic feasibility is one of the significant parameters in commercialization, the primary cost of LIG comes from the carbon substrate and the laser system as the electricity cost for laser usage is low.[169] According to Thamaraiselvan et al., the capital cost for making 1 m2 of LIG membrane at a laboratory scale is $1.[169] This cost might reduce in scaling up to the industrial amounts. In addition, Gupta et al. claim the cost of LIG composite membranes to be around $4–5/m2.[170] This also includes the cost of solvents and crosslinkers used to prepare membranes, which can further be reduced in bulk purchase. LIG can be printed on the waste such as biomass or other waste products, including wood and cardboards.[24] The incorporation of such precursors could lower down the cost even more. Apart from cost, the irradiation energy required for carbonization is ∼5 J/cm2, and <40 J/cm2 is required for the photothermal process for making various morphologies of LIG, including fibers.[60] This energy is far less as compared to the CVD process, which requires around 4–7 kWh/cm3 of the product formed, thus creating a sustainable footprint toward graphene manufacturing.[171,172]

In addition to the cost and energetics, the viability of scale-up production is required to deliver the mass and volume demands in practical applications. The techniques, including roll-to-roll processing and 3D printing, have shown their potential in manufacturing LIG in bulk.[173] The roll-to-roll process involves the production of consecutive LIG films along with the advancement of hybrid materials.[174] The carbon substrate is fed into the laser chamber with the help of a supply roll, and a 3D LIG film forms on two-sided irradiation.[173] In addition, the 3D printing method gives a platform for developing LIG monoliths via different routes. Usually, the formation of 3D macroscopic graphene is done on metallic foam, followed by metal removal, as shown by Chen et al.[175] However, due to the LIG technology, laser sintering and laminated objected manufacturing (LOM) could be equipped to produce graphene in a hassle-free manner. These techniques are widely used in additive manufacturing for the bulk production of materials. In laser sintering, metals and carbon-based mixtures are subjected to laser irradiation followed by the etching step.[176]

On the contrary, in LOM, the LIG films first adhere via ethylene glycol, followed by further lasing on top of the carbonaceous surface.[51,177] These techniques are unique in controlling the macroscopic features and shape of the substance via computer-based designs. Furthermore, the quality of graphene obtained by these methods has shown high conductivity and porosity.[173,176] The prevalence of lasers in high-throughput manufacturing is widely known and can be equipped to produce high-quality graphene for various applications. The major challenge lies in the selection of appropriate raw material and its modification for LIG. Table gives a brief summary of different substrates used to make LIG for sensing, antibacterial, and antiviral applications. Since a significant amount of research has been done with polyimide (PI) sheets, there is a need for exploring different carbonaceous materials, including biodegradable ones, for a better understanding of the manufacturing process and extrapolation to the fields.

Table 1

Summary of Various Carbon-Based Precursors and Their Laser Settings Used for Making LIG for Control and Preventive Technologies

starting material	laser type	lasing parameters for LIG fabrications	application	modification/functionalization type	properties induced	refs
Polyimide	10.6 μm CO2 laser	power = 22%	glucose biosensor	lactase oxidase and glucose oxidase (type VII) with chitosan	high specificity and selectivity	(178, 179)
		speed = not mentioned
		power = 1%	sweat glucose biosensor	Pt nanoparticles with chitosan and glucose oxidase	high conductivity and charge transfer resistance	(180)
		speed = 10%
		power = 9.6 W	point-of-care diagnosis	aptamer with thrombin-receptive interface	high capacitive response and selectivity	(181)
		speed = 15 cm/s
		power = 7.5	antibacterial surfaces	low-density polyethylene (LDPE)	superhydrophobic	(51, 182)
		speed = 30 cm/s
		power = 9–11.5 W	air filters	no functionalization	antimicrobial, self-sterilizing	(29, 95)
		speed = 30 cm/s
		power = 10%	wearable sensor	electroless Ni plating, polyurethane	enhanced sensitivity, piezoelectric effect	(183, 184)
		speed = 10–11%
	micromachining laser, 10.6 μm CO2 laser	power = 3 W	pathogen detection	Pt, Au, Ag NPs with chitosan hydrogel ink, antibodies with metal nanoparticles	excellent sensitivity, stability and flexibility	(185, 186)
		speed = 2–5 cm/s
	10.6 μm CO2 laser, fiber laser	power = 1.8–3 W	face masks	AgNO3, GO, and TiO2, dual-mode continuous wave (CW) laser-induced forward transfer (LIFT) method	photothermal effect superhydrophobic	(97, 187, 188)
		speed = 40–100 cm/s
Polyether sulfone (PES)	10.6 μm CO2 laser	power = 0.05–2 W	antimicrobial surfaces and membranes	sulfur-doping, PVA/glutaraldehyde/GO, AgNO3	antimicrobial, antibiofouling, bactericidal	(25, 27, 66, 70, 73, 109, 170)
		speed = 10–30 cm/s
Polyether ether ketone (PEEK)	10.6 μm CO2 laser	power = 50%	antimicrobial surfaces	MoOx-metal NPs	antibacterial, biocompatible	(189)
		speed = 10 cm/s
Miscellaneous materials: wood, water color paper	10.6 μm CO2 laser, 355 nm UV laser	power = 3–6 W	antimicrobial surfaces	polyimide-dichloromethane (DCM)-inert atmosphere, Ag and ZnO nanocrystals	superhydrophilic, bacteriostatic, antibiofouling	(190, 191)
		speed = 10–100 cm/s

Summary and Conclusions

The COVID-19 pandemic has meticulously imprinted its side effects on the environment; be it directly or indirectly, it has impacted human health adversely. The control and prevention of this highly contagious viral spread become indispensable at the beginning when it acquires different routes of transmission. The overexploitation of resources has also become a serious issue nowadays and requires material management to a greater extent. There comes the need for sustainable materials, encompassing properties such as easy fabrication, resource efficiency, low cost, environmental nonhostility, and low energy requirement. Laser-induced graphene is a versatile material embodied with all these features. LIG could be prepared via single-step laser scribing without the need for any additional chemicals. Its nanofibrous texture and sharp edges induce potent antibacterial activity, further enhanced by incorporating metal and metal oxides. Due to high conductivity, it also shows captivating joule heating properties along with self-sterilization applications in air and water. This was also envisioned against coronaviruses HCoV-OC43 and HCoV-229E, and complete killing of the virus occurred within 15 min of photothermal action.

In addition to that, it also offers superior electrochemical properties due to its low oxygen overpotential.[192] On exposure to electricity, the generation of hydrogen peroxide occurs, which creates oxidative stress in the microbes, leading them to die. However, a high voltage is required for viruses due to their complex structure. LIG electroconductive filters were also fabricated, which can be used at high flux when coated with PVA and GO. At a high flow rate and in flow-through mode, these membranes completely removed the microorganisms. Their antiviral and antibacterial properties can be utilized in applications ranging from antiviral surfaces to membrane-based electrochemical disinfection devices. The low heat capacity of LIG promotes easy heat gain and loss from the materials, which can be utilized in making antiviral surfaces. The shape-controlling feature provides custom-tailored fabrication, which can be optimized via laser settings. Also, its high nucleobase adsorption and charge transfer capacity make it suitable for biosensing applications. Due to the high commercialization aspects and easy fabrication of LIG, electrochemical, optical, and biosensing could be explored for water, air, and soil monitoring. Additionally, LIG could be incorporated in membrane-based technology for air, water, and sludge management with real-time monitoring through sensors. The texture, conductivity, and robustness of the membrane surface can be optimized for better performance. Overall, LIG has attracted researchers toward its promising self-sterilization and easy and versatile preparation, which demands extensive research in devising its implementation toward control and preventive technology. LIG’s low-cost, low-energy, single-step fabrication, eco-friendliness, and sustainability aspects make it an innovative and sustainable material to restrain COVID-19 or similar pandemics in the environment.