A galinstan-based inkjet printing system for highly stretchable electronics with self-healing capability.

We report a galinstan-based inkjet printing system to realize highly stretchable electronics with self-healing capability. The printing head made of polydimethylsiloxane (PDMS) consists of a main microfluidic channel and a coplanar channel. The main channel containing the oxidized galinstan is surrounded by the coplanar channel, which is filled with HCl. The HCl vapor effectively permeates the channel wall due to the high gas permeability of PDMS. The oxide skin of galinstan is consistently removed by chemical reaction with the HCl vapor. This allows one to maintain galinstan in a true liquid phase in the main channel. After the fabrication of the printing head with PDMS, the sizes of droplets ejected from the printing head with various flow rates have been characterized. The fabricated inkjet printing system is also utilized to generate complex galinstan patterns on various substrates. An LED-integrated circuit with self-healing capability shows excellent electrical and mechanical performance even after it is twisted more than 180° or stretched up to ∼60% more than 2000 times. The experimental results reveal that the proposed system has tremendous potential for stretchable electronic applications in the future.