BACKGROUND: Although the most supportive sports bras can control breast motion and associated breast pain, they are frequently deemed uncomfortable to wear and, as a result, many women report exercise bra discomfort. Given that exercise bra discomfort is associated with decreased levels of physical activity, there is a pertinent need to develop innovative solutions to address this problem. OBJECTIVES: This research aimed to evaluate the use of electromaterial sensors and artificial muscle technology to create a bra that was capable of detecting increases in breast motion and then responding with increased breast support to enhance active living. METHODS: The research involved two phases: (i) evaluating sensors suitable for monitoring and providing feedback on changes in the amplitude and frequency of breast motion, and (ii) evaluating an actuator capable of changing breast support provided by a bra during activity. RESULTS: When assessed in isolation, the developed technologies were capable of sensing breast motion and actuating to provide some additional breast support. CONCLUSIONS: The challenge now lies in integrating both technologies into a functional sports bra prototype, and assessing this prototype in a controlled biomechanical analysis to provide a breast support solution that will enable women to enjoy active living in comfort.
BACKGROUND: Although the most supportive sports bras can control breast motion and associated breast pain, they are frequently deemed uncomfortable to wear and, as a result, many women report exercise bra discomfort. Given that exercise bra discomfort is associated with decreased levels of physical activity, there is a pertinent need to develop innovative solutions to address this problem. OBJECTIVES: This research aimed to evaluate the use of electromaterial sensors and artificial muscle technology to create a bra that was capable of detecting increases in breast motion and then responding with increased breast support to enhance active living. METHODS: The research involved two phases: (i) evaluating sensors suitable for monitoring and providing feedback on changes in the amplitude and frequency of breast motion, and (ii) evaluating an actuator capable of changing breast support provided by a bra during activity. RESULTS: When assessed in isolation, the developed technologies were capable of sensing breast motion and actuating to provide some additional breast support. CONCLUSIONS: The challenge now lies in integrating both technologies into a functional sports bra prototype, and assessing this prototype in a controlled biomechanical analysis to provide a breast support solution that will enable women to enjoy active living in comfort.
Entities:
Keywords:
Breast support; actuators; breast biomechanics; sensors/sensor applications; sports bra; wearable devices
The female breast contains limited anatomical support and, therefore, external
assistance in the form of a bra is typically recommended to control breast
motion.[1,2]
Although the principal purpose of a bra is to support the breasts, most bras
designed for everyday wear represent a compromise between this supporting function,
the need for comfort, and aesthetics to enhance a woman’s breast shape. During tasks
in which vertical movement of the upper body increases, such as in jogging or
running, the demands on a bra with respect to providing breast support increase. For
example, past research has found that vertical breast displacement can increase by
more than 42 mm when a woman (bra size 14C; Australian bra sizing system) runs in an
everyday bra compared to walking in the same bra.[3] As increases in vertical breast displacement as little as 20–30 mm have been
repeatedly linked to breast pain and discomfort, it is recommended that women wear a
sports bra when exercising.[3-6]Sports bras are designed to restrict vertical breast movement by encapsulating the
breasts and/or compressing them against the chest wall. Sports bras achieve this
function, in part, by using fabrics that are stiffer and allow less stretch than the
fabrics used in everyday bras.[7] In an evaluation of several sports bra styles, Lawson and Lorentzen[4] reported that bras that were rated highly in terms of support were made from
firm, low-stretch materials, whereas bras that used softer, highly elastic materials
were poor at controlling breast motion. This research also highlighted that the
physical characteristics of a sports bra that enables it to limit breast motion,
such as firm, low-stretch materials, also tend to make the sports bra more
uncomfortable to wear.[4]A sporting activity or an exercise regime can include periods of activity when the
additional support offered by a sports bra is desirable, in combination with periods
of relative inactivity, when support is not as necessary. Ideally, in these
situations a sports bra should relax during inactivity to improve wearer comfort.
Similarly, an everyday bra might provide sufficient support during many activities
of daily living or work, such as sitting relatively stationary at a desk, but
situations can arise when additional breast support is unexpectedly required, such
as having to run to catch a bus. These scenarios demonstrate that the potential
exists for a bra design that can respond to the needs of the wearer by changing its
physical characteristics to provide more support during higher levels of physical
activity and then relaxing into a more comfortable state during periods of relative
inactivity. Such a bra would require a ‘sensor’ that is responsive to a change in
breast movement and an ‘actuator’ that can be triggered by the sensor and adjust the
supportive elements in the bra.Polypyrrole-coated textiles, in which a base fabric is coated with the conducting
polymer, polypyrrole (PPy), have been found to be effective wearable strain gauges
with a high linear dynamic range and gauge factors similar to conventional strain
gauges.[8,9]
Textile-based sensors using this technology are relatively inexpensive to
manufacture and can be applied to commercial high-stretch fabrics that conform to
the body, making them ideal to incorporate into a wearable garment for
bio-monitoring purposes.[10,11] More specifically, our previous work indicated that a
PPy-coated textile sensor, when pre-stretched by 20% of its initial length, was able
to accurately and reliably monitor changes in the amplitude and frequency of
vertical breast displacement when the sensor was attached appropriately to the
wearer’s bra.[12] Problems exist, however, when using these PPy fabric sensors. The textile
sensor: (i) needs to be pre-strained to 20% before being placed on the bra because
this is within the linear regime of the sensor response; (ii) displays recoil that
produces a double peak in the sensor reading at the end of the stretch
cycle/beginning of the unloading cycle; (iii) has a small response lag during
measurements, thought to be caused by changes within the textile geometry, and (iv)
the signal drifts over time with textile creep and exposure to the environment,
making ongoing calibration of the sensor a necessity.[12]In an attempt to alleviate the issues associated with PPy-coated textile sensors, we
investigated the use of an encased polypyrrole mechanical bending sensor, composed
of PPy layers either side of a polyvinylidine fluoride (PVDF) porous membrane filled
with electrolyte,[13,14] which could also potentially be used to monitor breast motion.
In this arrangement, a bending displacement of these thin film sensors generates a
small electrical potential difference in the millivolt range, providing a
mechanoelectrical output. These structures are fully encapsulated in a flexible
coating to increase device stability and improve immunity to the environment.[15] Here we investigate the use of encapsulated bending sensors for their
suitability to measure breast movement amplitude and frequency for the purpose of
triggering an actuator in a responsive bra.In addition to sensing a change in breast movement, the proposed responsive bra must
also be capable of physically adapting in response to the sensor input to provide an
appropriate level of breast support. Recent advances in artificial muscle research
have produced ‘Baughman muscles’, which consist of thermally driven coils made from
low cost polymer fibres, such as nylon fishing line and polyester sewing thread that
are capable of contracting by up to 49%.[16] Specifically, an actuating textile can be produced by weaving conventional
polyester, cotton and silver-plated nylon yarn (to drive the electrothermal
actuation) through a parallel assembly of Baughman muscles.[16] We postulate that such an actuating textile, when positioned appropriately on
a bra, has the capacity to modify breast support by changing bra tightness.Incorporating the above-mentioned sensor and actuating technologies into a bra so it
can respond to a wearer’s needs and provide the appropriate level of support for
women when they are active appears possible. Therefore, the aim of this research was
to investigate the feasibility of integrating electromaterials into a bra to create
a garment that can change its physical characteristics and alter the level of breast
support in response to changes in breast motion. We call this system the ‘Bionic
Bra’. To achieve this aim, the research involved two phases: (i) identifying a
sensor suitable for monitoring and providing feedback on changes in the amplitude
and frequency of breast motion, and (ii) identifying an actuator capable of changing
breast support provided by a bra during activity. It was hypothesised that: (i)
sensors made from electromaterials would be able to detect changes in the amplitude
and frequency of breast motion during activity, and that (ii) actuators made from
electrothermally driven Baughman artificial muscles could contract to tighten the
bra sufficiently to increase breast support.
Experimental methods
Fabrication of the bending sensors
Polypyrrole (PPy)-based tri-layer bending sensors were fabricated as described in
detail previously.[13] Briefly, a PVDF porous filter membrane (millipore of nominal 0.45 µm pore
size, 75% porosity and ∼110 µm thickness) was sputter coated on both sides with
platinum. Polypyrrole was deposited galvanostatically at a current density of
0.10 mA cm–2 for 12 h on the Pt surfaces from a polymerisation
solution containing pyrrole monomer (0.06 M, Merck, freshly distilled) and
tetrabutylammonium hexafluorophosphate (0.05 M, TBA.PF6, Aldrich) in propylene
carbonate (99.7% anhydrous, Aldrich). Following electrodeposition, all edges of
the as-prepared bulk membrane were trimmed off and then cut to small strips
(20 mm × 1 mm) using a scalpel blade, ensuring that the two PPy layers on
opposite sides of the PVDF membrane were not in electrical contact. The sensor
was then encapsulated between two pieces of adhesive tape cut to slightly larger
than the sensor dimensions.
Sensor evaluation
For qualitative human testing, the sensor was encased in adhesive tape and
attached to the inferior aspect of the cup of an everyday bra (Brand: Berlei,
Style: Touched, Size: 14 C), worn by a participant as she walked and jogged on a
treadmill at 7 kph. The mechanical bending sensor relies on deformation to
generate a signal and is designed to deform principally in bending and twisting
modes. For this reason, we positioned the sensor on the bra so that breast
motion was most likely to apply a force to bend the sensor. The sensor was
therefore attached to the inferior aspect of the bra cup because: (i) the sensor
could detect a change in curvature of the bra cup rather than stretch; (ii) the
sensor was fully conformed to the bra cup; (iii) breast tissue was always in
contact with the bra material at the base of the bra cup thus ensuring a
continuous signal, and (iv) a large increase in the amount of ‘downward’ breast
motion was observed as the participant changed from a walk to a run.
Baughman muscle coiled fibre fabrication
Actuating fibres for this experiment were fabricated from 0.4 mm diameter
monofilament nylon 6 fishing line. A length of fibre was attached vertically to
a rotary tool whilst the other end was tethered to prevent rotation, but allowed
to move vertically. A load of 300 g was also attached to the bottom end to apply
tension and prevent unfavorable ‘snarling’ of the fibre (snarling occurs when
the end is unrestrained and over-twists onto itself). Twisting was applied until
coil propagation occurred, at which point the twisting rate was lowered to
ensure the filament would not break and twisting continued until the entire
fibre was coiled. The coiled fibre was then attached at both ends to a rigid
board at a neutral length and subject to thermal treatment in an oven at 150℃
for 2 h. Whilst the coiled fibre was still hot, it was stretched to 5–10% strain
and anchored. A further heat treatment at 150℃ for 1 h was applied to set the
fibre in place. Several cycles of stretching and heat treatment were performed
until the fibre reached 150% of its original length, ensuring the coils were
suitably separated (Figure
1).
Figure 1.
(a) Untreated coiled fibre. The frequency of coils can be observed to
be 1.5 × greater than a heat-treated coil. (b) Fibre after heat
treatment cycle, stretched out to 150% strain.
(a) Untreated coiled fibre. The frequency of coils can be observed to
be 1.5 × greater than a heat-treated coil. (b) Fibre after heat
treatment cycle, stretched out to 150% strain.In some cases the nylon monofilament fibre was co-twisted with a longer length of
silver coated nylon multifilament yarn (Shieldex, USA). The conductive yarn was
tightly wrapped around the monofilament and provided a means for electrical
heating.
Textile actuating device fabrication
The housing of the textile-actuating device was prototyped using additive
fabrication (Objet Connex350, ABS-stimulant material; Figure 2). Segmented lengths of fibres
were attached to the device housing using UV curable methacrylate glue,
embedding the fibre within the device itself. A three-dimensional (3D) printed
loom and shuttle were used to weave cotton fibre through the actuating fibres to
reinforce the lateral component of the structure. Silver-coated nylon was also
woven into the structure perpendicular to actuating fibres, with approximately
5 mm spacing between the strands, to provide a heating element for actuation
(Figure 3). Thermal
resistors (thermistors) were stitched into the fabric to allow accurate thermal
monitoring. Interconnects between the silver coated nylon and electronics were
formed by using water-based wire glue to adhere the fibres to metal pins.
Finally, control of the device was achieved using a Freetronics Leostick
microcontroller (Freetronics Pty Ltd, Croydon Hills, Australia). A feedback loop
was set up where the temperature of the fabric was determined and
transistor-regulated current allowed to pass through the silver-coated nylon
only if the temperature was below a pre-set threshold. The actuating textile
only generates a contractile force in the direction of the actuating Baughman
muscle fibres. Therefore, the actuating textile is positioned on the bra to
maximise the effectiveness of this force generation.
Figure 2.
Rapidly prototyped low-profile device housing, designed to utilise
readily available hook and eye fasteners. Commercially available bra
hook fasteners were fixed into one end of the housing, with the
actuator fixed onto the other end. Bra eye fasteners were sewn onto
the sample sports bra, allowing the actuator device to be placed and
stretched to different initial loadings.
Figure 3.
Close-up photograph of fabric structure showing cotton support fibres
woven perpendicular to actuating fibres, and silver-coated nylon
woven through to provide the heating element for actuation.
Rapidly prototyped low-profile device housing, designed to utilise
readily available hook and eye fasteners. Commercially available bra
hook fasteners were fixed into one end of the housing, with the
actuator fixed onto the other end. Bra eye fasteners were sewn onto
the sample sports bra, allowing the actuator device to be placed and
stretched to different initial loadings.Close-up photograph of fabric structure showing cotton support fibres
woven perpendicular to actuating fibres, and silver-coated nylon
woven through to provide the heating element for actuation.
Actuation testing
The textile-actuating device and individual actuator fibres were characterised
using temperature-dependant force calibration plots. A known length of fibre or
textile was mounted at zero strain into an EZ Mechanical Tester (Shimadzu Ltd,
Kyoto, Japan). The machine was set to measure force over time, while maintaining
a constant strain. Current was applied at constant voltage to the silver-coated
nylon wrapped around the coiled fibres or woven into the actuating textile.
Alternatively, the sample was enclosed in a small tube furnace for controlled
heating tests. Temperature and force were recorded as a function of time, with a
linear response within a target operational range of ambient room temperature
to < 80℃ (the maximum temperature deemed safe for use in the bra
application). Fibre or textile temperature was recorded using an infrared
thermal imaging camera (Micro– EPSILON, TIM160) and thermistor (Honeywell 100 K
Thermistor, 135-104LAG-J01).
Results
Clean electronic signals were obtained from the bending-type sensors. The
amplitude of the signal voltages (minimum peak to maximum peak) between walking
(0.4 mV) and running (5 mV) were obvious and clearly distinct from the
background electronic noise (Figure 4). The recoil observed with the PPy coated textile sensor[12] was absent. Therefore, it was concluded that the bending sensor was
superior to the PPy coated textile sensor due to greater sensitivity to small
strain values, low noise and minimal signal drift. In addition, as the sensor
was encased it showed improved immunity to the environment compared to the
textile sensors. This is important because wearable sensors need to be robust
against external physical, electrical and electromagnetic disturbances, as well
as impervious to factors such as sweat, moisture, and temperature fluctuations.[17] Currently, the small output signals of the bending sensors are detected
by hardwiring directly to a high-quality laboratory data collection system.
Further work is required to develop appropriate electronics for on-board signal
amplification and transmission.
Figure 4.
Raw voltage output from the mechanical bending sensor located on the
inferior aspect of the bra cup for the participant (bra size 14C)
walking and jogging (both at 7 kph).
Raw voltage output from the mechanical bending sensor located on the
inferior aspect of the bra cup for the participant (bra size 14C)
walking and jogging (both at 7 kph).
Actuator evaluation
Evaluation of force generation
Both individual Baughman muscle fibres and actuating textiles were evaluated
for their force generation. As shown in Figure 5(a), a maximum force
of ∼ 0.7 N was achieved within 5–6 s in a single coiled fibre using an
electrical input of 12.0 V (at approximately 250 mA with supply current
varying slightly, due to variation in the heating element resistance). The
electrical heating increased the coiled fibre temperature from ambient to
around 80℃ and the force generated closely tracked the measured temperature.
Adjusting the input electrical power controlled the rate of heating and
maximum force generated. The device relaxed back to near the base-line force
(approximately 0.03 N) upon cooling. These results were confirmed by furnace
heating tests (Figure
5(b)) where individual coiled fibres (without a wrapped heating
element) generated approximately 0.6 N when heated to from 25℃ to 75℃. The
results also indicate that forces of up to 3 N could be attained from the
textile-actuating device consisting of nine parallel polymer coils when
electrically heated to ∼ 80℃ (Figure 6). Force generation increased
with temperature and a maximum force of 6.5 N was achieved at a fabric
temperature of 135℃. At the same measured temperature of ∼ 80℃, the textile
actuating band with nine parallel actuating coiled fibres generated
approximately five times the force of a single actuating fibre. Uneven
heating of the fibres due to the sparsely woven electrical heating fibre in
the textile is likely to have contributed to the slightly lower than
expected force. Further improvements to the heating elements included in the
actuating textile are currently under investigation.
Figure 5.
Force and temperature response curves for a single actuating
coiled Baughman muscle fibre electrically heated when 12 V was
applied to the silver-coated nylon yarn wrapped around the
Baughman muscle (a) or when heated to 75℃ in a
temperature-controlled oven (b).
Figure 6.
Force and temperature response curve for an actuating textile.
Power was supplied to the heating element for 1 min, and then
the current was removed and the actuator returned to a relaxed
stretched length.
Force and temperature response curves for a single actuating
coiled Baughman muscle fibre electrically heated when 12 V was
applied to the silver-coated nylon yarn wrapped around the
Baughman muscle (a) or when heated to 75℃ in a
temperature-controlled oven (b).Force and temperature response curve for an actuating textile.
Power was supplied to the heating element for 1 min, and then
the current was removed and the actuator returned to a relaxed
stretched length.
Evaluation of an actuator device integrated into a bra
Two textile actuating devices were placed horizontally and in parallel on the
back of a commercially available compression sports bra (Brand: Champion,
Style: WB2374, Size: Medium; Figure 7), worn by a female
participant (age = 20 years, mass = 68.2 kg; height = 1.61 m; bra
size = 12 E). The bra was fitted to the participant according to
professional bra fit criteria.[18] Although fitted, subjective feedback from the participant indicated
that she felt the bra did not compress her breasts enough to limit her
breast motion during exercise. The purpose of this actuator position was to
assess whether textile device actuation could increase the level of breast
compression while the participant stood stationary and while running on a
treadmill. Breast compression by the bra was evaluated by measuring the
pressure exerted on the participant’s torso by the bra side band. To assess
changes in left and right band pressure during the static standing trials,
two calibrated Pliance® pressure mats (4 × 16 cm2 sensors;
novel®, Munich, Germany) were adhered directly onto the participant’s torso,
extending from the edge of her breast tissue towards her back on both sides
of her torso. Two trials of mean bra band pressure data (N/cm2;
10 s each) were then collected with the actuator device de-activated (Figure 8). The
actuator device was then activated and a further 10 trials of pressure data
(10 s each) were collected with the actuator ‘on’, in order to examine the
pressure sustained over this period of time.
Figure 7.
Two actuator systems placed in parallel on the back band of a
bra. Electrical connections for powering the actuator systems
are shown.
Figure 8.
Mean bra band pressure (N/cm2) measured for one
participant before and after the bra actuator was activated,
over 12 trials (10 s each).
Two actuator systems placed in parallel on the back band of a
bra. Electrical connections for powering the actuator systems
are shown.Mean bra band pressure (N/cm2) measured for one
participant before and after the bra actuator was activated,
over 12 trials (10 s each).Following pressure data collection, the actuator device was switched off and
a short break (∼2–5 min) was taken for the actuator to cool down and to
allow the bra to return to its original state. The participant then ran on a
treadmill (SportsArt T650ME, Tainan City, Taiwan) at 10 kph for 3 min
duration. Immediately after running, the participant was asked to mark her
perceived levels of bra discomfort, perceived breast motion, and any
associated breast motion discomfort on a 5 inch visual analogue scale (VAS)
with no discomfort or movement at the ‘0’ end of the scale, and worst
possible discomfort or extreme movement at the ‘5’ end of the scale. The
actuator device was then activated and the running trial and associated VAS
data collection were repeated.Mean pressure for the left and right bra bands were averaged to produce the
total mean bra band pressure over the 12 trials. As expected, bra band
pressure increased significantly when the actuator was activated, and
maintained this level of pressure throughout activation (Figure 8). Before
activation, the bra band exerted a mean pressure of slightly more than
1 N/cm2 due to elastic stretching of the bra material.
Activation of the actuators increased this mean pressure by ∼ 50% to
1.5 N/cm2 by further stretching the bra material around the
wearer’s torso. Subjective data presented in Table 1 indicated that the
participant was able to perceive the change in breast support provided by
tightening of the bra as the actuator was activated, and this resulted in
improved breast and bra comfort, as well as a perceived decrease in breast
movement during running.
Table 1.
Subjective visual analogue scale (VAS; 0–5 scale) data for one
participant’s perceived breast movement, breast discomfort and
bra discomfort, when the actuator was de-activated and
activated.
Actuator status
Breast movement
Breast discomfort
Bra discomfort
De-activated
3.5
3.8
2.9
Activated
2.6
2.9
1.9
Subjective visual analogue scale (VAS; 0–5 scale) data for one
participant’s perceived breast movement, breast discomfort and
bra discomfort, when the actuator was de-activated and
activated.
Discussion
A bra that can respond to the needs of the wearer by changing its physical
characteristics to provide more support during higher levels of physical activity
and then relaxing into a more comfortable state during periods of relative
inactivity would foster the comfort of many women and, in turn, enhance active
living. Such a bra would require a ‘sensor’ that is responsive to an increase in
breast movement, and an ‘actuator’ that is responsive to output from the sensor and
could adjust the supportive elements in the bra. This study aimed to identify a
sensor suitable for monitoring and providing feedback on increasing amplitude and
frequency of breast motion, and to identify an appropriate actuator that when
activated was capable of increasing the breast support provided by a bra. Results of
this research confirm that sensors made from electromaterials were able to detect
changes in the amplitude and frequency of breast motion during walking and running.
Furthermore, actuators made from electrothermally driven artificial muscles could be
initiated to contract, tightening the bra, and providing additional breast support
for the wearer. Practicalities and implications associated with these results are
discussed below.The efficacy and limitations of PPy-coated textile sensors in detecting breast motion
have been published elsewhere,[12] and so this study focused on use of a more robust encased polypyrrole
mechanical bending sensor. Although PPy-coated textile sensors provide output based
on stretch, as the name implies, the mechanical bending sensor relies on bending to
generate a signal. For this reason, the mechanical bending sensor was positioned
where breast displacement was most likely to bend the sensor. Results of the present
study established that placing the mechanical bending sensor around the curved area
at the base of the bra cup (placed vertically from the most inferior portion of the
bra cup to 1.5 cm below and 1 cm lateral of the nipple away from the sternal line;
Figure 4) provides very
clean electronic signals with clear signal differences between walking and running.
Therefore, these sensors could be integrated into a Bionic Bra design to indicate a
change in the amplitude of breast motion. Their exact placement, however, would
depend on ease of integration, as well as identifying a part of the bra that was
least likely to fail, and a location that would not interfere with or cause
discomfort to the breasts. For example, respondents may not like an active component
sitting directly on top of their breast tissue. Table 2 summarises some aspects that should
be considered when deciding which sensor might be most suitable to integrate into a
Bionic Bra design.
Table 2.
Aspects to consider when choosing either the PPy coated textile stretch
sensor or the PPy film type-bending sensor in the Bionic Bra
application.
Fabric Stretch Sensor
Film Bending Sensor
Soft fabric construction (nylon Lycra) that does not
increase stiffness of bra structure
Need to be encased to prevent drying of the electrolyte in
the sensor, resulting in additional stiffness to the bra cup
compared to the fabric sensor
Signal drift due to changing electrical properties of PPy
coating due to: ^ inherent ‘creep’ of base textile ^ ‘aging’
of the coating and ‘stretching’ of the original fabric
sample after repeated elongation, especially at larger
strains ^ environmental instability of the conducting
coating, especially in humid environments
Minimal signal drift as these sensors do not ‘age’ like the
fabric sensors. They are protected from the environment by
the casing.
Best positioned vertically from the most superior portion of
the bra strap to 4 cm above the nipple; sensor length
approximately 120-135 mm
Best positioned vertically from the most inferior portion of
the bra cup to 1.5 cm below and 1 cm lateral of the nipple
away from the sternal line; sensor length approximately
30-40 mm
Need to pre-strain to 20% for there to be a linear change in
resistance with strain. A larger strain amplitude is needed
to elucidate the signal from the electronic ‘noise’
originating from the baseline drift, natural creep of the
nylon Lycra fabric and the ‘recoil’ effect
Can detect signals at lower strains due to a low noise
signal and no inherent creep within the sensor
Reference voltage to induce signal (battery required)
No battery required in principle (energy harvesting)
Signal requires no amplification (output in V)
The signal may require amplification in the circuit (output
in mV)
Aspects to consider when choosing either the PPy coated textile stretch
sensor or the PPy film type-bending sensor in the Bionic Bra
application.This was the first study to examine the efficacy of Baughman coiled polymer fibre
artificial muscles as actuators for tightening a bra, and the results are promising.
Bench top analysis revealed that the actuators produced up to 3 N of force when
electrically heated to ∼ 80℃. When integrated into a bra, the actuator elements
caused a ∼ 50% increase in bra band pressure on the wearer’s torso. Subjective
feedback indicated a slight decrease in perceived breast movement, and an increase
in breast and bra comfort following actuator activation. Further research is
therefore needed to confirm or refute these results in an appropriately powered
sample of participants of varying breast size. Furthermore, objective measures of
breast motion, such as vertical breast displacement, should be also incorporated
into future research to ascertain whether the increased bra band pressures were
sufficient to decrease breast motion. Nevertheless, these results indicated that
Baughman muscles could be initiated to contract, tightening the bra to provide
additional support to the wearer, and there is scope for further investigation in
the use of coiled artificial muscles in bra technology.Despite the evidence showing that a sensor can detect changes in breast motion and an
actuator can be activated to tighten the bra to provide more perceived support,
integrating these components into a wearable garment, that can be washed and worn,
remains challenging. Essentially, the electronics for such a bra would need two
components, a circuit used to amplify the signal supplied by the sensor and a
circuit used to deliver control signals to the actuator. Furthermore, the sensor
would need to be coupled with the actuator, with electronics that could integrate
the sensor information and provide information to the actuator to respond, and all
components would need to be powered. Although the electrical input to power the
actuator is at a low level, future developments would incorporate an electrical
insulation coating to avoid any issues with short-circuiting and to improve
durability. The future prototypes would also require temperature-sensing elements
for feedback control and to prevent any excessive force application.Being such a sensitive part of the body, there are likely to also be concerns about
where electronics and batteries are placed on the bra and women might prefer not to
have any active components placed on or around their breast tissue. These
restrictions mean that active components may need to be placed in other areas of the
bra, most likely on the bra band on the wearer’s back. Furthermore, given a bra is
such a personal item of apparel, support must be considered subjectively as well as
objectively. That is, how comfortable a bra feels to the wearer is a key outcome for
any bra design study, and the perceptions of the wearer towards the look and feel of
the bra must be carefully considered in the ultimate design of a Bionic Bra. We
emphasise that this manuscript is focussed on demonstrating the proof of principle
of a responsive bra concept. Further development is needed to build a practical
device including the appropriate electrical components, wiring, power supply and to
solve issues relating to washability, durability and aesthetics.Finally, adequate breast support is unlikely to be achieved by any one sports bra
structure or design across a range of breast shapes and sizes.[5] The ability to change the physical characteristics of a bra might therefore
still be limited by the inherent structural design of the bra. Although the Bionic
Bra revolutionises the sports bra concept towards providing a bra that responds to
the individual needs of women to minimise bra discomfort, much work is still
required to design better bra structures to accommodate this technology.
Conclusion
Highly supportive sports bras, while effective in controlling breast motion and
associated breast pain, are deemed uncomfortable to wear, and as a result many women
report exercise bra discomfort. Given that exercise bra discomfort is associated
with decreased levels of physical activity, there is a pertinent need to develop
innovative solutions to address this problem. Using electromaterials and artificial
muscle technology to create a bra that is comfortable to wear, but capable of
detecting increases in breast motion, and respond with increased breast support,
might provide a solution. These sensor and actuator technologies were developed and
evaluated for this specific purpose in this study, and results indicate that, when
assessed in isolation, the technologies are capable of sensing breast motion and
providing some additional breast support. The challenge now lies in integrating both
technologies into a functional Bionic Bra prototype, and assessing this prototype in
a controlled biomechanical analysis. Furthermore, due to the highly personal nature
of bras, consumers must be engaged to ensure the final prototype meets its objective
goals of responding to, and reducing breast motion, as well as the subjective
criteria of comfort, fit and aesthetics. When successful, the Bionic Bra will
transform sports bra technology, and provide a solution that will enable women to
exercise in comfort and, in turn, enhance active living.
Authors: Carter S Haines; Márcio D Lima; Na Li; Geoffrey M Spinks; Javad Foroughi; John D W Madden; Shi Hyeong Kim; Shaoli Fang; Mônica Jung de Andrade; Fatma Göktepe; Özer Göktepe; Seyed M Mirvakili; Sina Naficy; Xavier Lepró; Jiyoung Oh; Mikhail E Kozlov; Seon Jeong Kim; Xiuru Xu; Benjamin J Swedlove; Gordon G Wallace; Ray H Baughman Journal: Science Date: 2014-02-21 Impact factor: 47.728
Authors: Krista M Nicklaus; Karen Bravo; Chi Liu; Deepti Chopra; Gregory P Reece; Summer E Hanson; Mia K Markey Journal: Support Care Cancer Date: 2020-03-25 Impact factor: 3.603