Mechanically‐Guided Structural Designs in Stretchable Inorganic Electronics

Abstract

but remove the constraints of rigid, brittle, planar, wafer substrates, through the strategic integration with soft elastomers. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Compared with the conventional rigid devices, stretchable inorganic electronics not only allow large deformations without degradation in electronic performances, but also yield conformal integration with the complex surfaces of tissues of the human body. [8,[15][16][17][18][19][20] Due to these unique advantages, stretchable inorganic electronics technologies significantly broaden the application areas of conventional electronics, and also enable novel uses in health monitoring, advanced humanmachine interfaces and internet of things, such as epidermal electronics, [21][22][23][24][25] curvilinear electronics, [26][27][28] deformable optoelectronics, [29][30][31][32][33][34] transient electronics, [35][36][37] and many other bioelectronic systems. [38][39][40] With a series of rapid developments over more than a dozen of years, stretchable inorganic electronic systems now define a well-recognized and active field of study, encompassing a diverse range of fundamental and applied topics, [41][42][43][44][45][46][47][48][49][50][51][52][53] including, for example, a collection of unusual material/structure designs and techniques to integrate hard inorganic semiconductor components and geometrically structural interconnects in optimized layouts onto patterned soft substrates. [7,54,55] Stretchable electronics have achieved high levels of sophistication largely through the use of inorganic active materials. According to the utility of different conductive materials, stretchable inorganic electronics can be classified into three categories, including those based on the composite stretchable conductors, liquid metals, and structured semiconductors/metals. [49,[56][57][58] In the first category, novel nanomaterials dispersed into a polymer matrices form composite films or fibers, by coating, dipping, printing, and electrospinning. Various nanomaterials have been exploited in this context, including metal nanoparticles, nanowires, nanoflakes, and the allotropes of carbon (carbon nanotubes, graphene, and carbon blacks). [59][60][61][62][63][64][65][66] A key to this strategy is in maintaining interconnected pathways through these nanomaterials to enable highly conductive channels when the substrate is stretched. [67][68][69][70][71] Despite great progress, the conductivities of such composites are typically lower than those of conventional metals. The second category of stretchable inorganic conductors relies on liquid metals patterned and encapsulated into channels of elastomeric materials. [72,73] Such constructs can be bent and stretched to levels beyond those possible with conventional electronic materials.Over the past decade, the area of stretchable inorganic electronics has evolved very rapidly, in part because the results have opened up a series of unprecedented applications with broad interest and potential for impact, especially in bio-inte...

Ink‐Based Additive Nanomanufacturing of Functional Materials for Human‐Integrated Smart Wearables

“…Cracking of the printed film under mechanical deformation represents a major failure mode for wearable devices. The incorporation of self-healing materials [1049][1050][1051][1052][1053][1054] and mechanically compliant structures [78,117,[1055][1056][1057][1058][1059][1060][1061] into the printed devices should be researched and explored to mitigate such mechanical failures.…”

Flexible inorganic bioelectronics

“…To be mechanically compatible, the stretchability and conformal contact are the basis for devices to be mechanically invisible to the human body. [69][70][71][72] With geometry designed strain limiting substrate, a device that resembles the stress-strain behavior of skin can be safe and comfortable in long-term wearing. [73][74][75] To be biologically compatible, devices working on the skin shall be breathable with the help of textile/micropores or nanofiber meshed membrane based substrate.…”

Hexahedral LED Arrays with Row and Column Control Lines Formed by Selective Liquid‐Phase Plasticization and Nondisruptive Tucking‐Based Origami

“…Recently developed “origami” technology is feasible for the fabrication of various transformable forms [ 1–4 ] for interdisciplinary applications, such as microelectromechanical systems, [ 5,6 ] optical devices, [ 7,8 ] artificial muscles, [ 9 ] mechanical metamaterials, [ 10,11 ] biomedical systems, [ 12,13 ] microfluidic paper devices, [ 14 ] energy storage/conversion systems, [ 15–18 ] and electronics. [ 19–36 ] The technology basically uses geometrical relief structures, such as trenches, [ 18,21,30 ] dashed cut lines, [ 8,20,22,26 ] and creases, [ 3,9,15,17,24,32,35 ] in the desired regions that can be deformed by simple external mechanical forces. Selective bending is also possible by using various actuators based on photoactive materials, [ 37–40 ] swelling materials, [ 41–43 ] shape memory alloys/polymers, [ 44–46 ] thermally expandable materials, [ 47–49 ] field‐responsive materials, [ 50–54 ] and prestrained materials.…”