Designing Thin, Ultrastretchable Electronics with Stacked Circuits and Elastomeric Encapsulation Materials

Abstract

Many recently developed soft, skin-like electronics with high performance circuits and low modulus encapsulation materials can accommodate large bending, stretching, and twisting deformations. Their compliant mechanics also allows for intimate, nonintrusive integration to the curvilinear surfaces of soft biological tissues. By introducing a stacked circuit construct, the functional density of these systems can be greatly improved, yet their desirable mechanics may be compromised due to the increased overall thickness. To address this issue, the results presented here establish design guidelines for optimizing the deformable properties of stretchable electronics with stacked circuit layers. The effects of three contributing factors (i.e., the silicone inter-layer, the composite encapsulation, and the deformable interconnects) on the stretchability of a multilayer system are explored in detail via combined experimental observation, finite element modeling, and theoretical analysis. Finally, an electronic module with optimized design is demonstrated. This highly deformable system can be repetitively folded, twisted, or stretched without observable influences to its electrical functionality. The ultrasoft, thin nature of the module makes it suitable for conformal biointegration.

Rollable, Stretchable, and Reconfigurable Graphene Hygroelectric Generators

“…In this regard, programmable laser treatment can easily construct bridge–island‐structured devices ( Figure a), where the unstretchable GHEGs (islands) are directly connected by electric conductive serpentine rGO interconnect (bridges). The GHEGs will remain undeformed when stretched, while the serpentine rGO interconnect undergoes lateral buckling to accommodate the applied strain, transforming high tensile deformation into bending deformation on bridges and resulting in large strength deformation of final device . Finite‐element analysis (FEA) reveals that the highest tensile strain of the device with three serpentine interconnect units is only 0.89% (Figure a), which is much lower than the critical strain at break of GO film (Figure S19, Supporting Information) .…”

Mechanical designs employing buckling physics for reversible and omnidirectional stretchability in microsupercapacitor arrays

“…Previous studies have shown that buckling and postbuckling deformation of thin films can greatly improve the reversible stretchability of interconnects [15,19,20]. Because the critical buckling strain (which is proportional to the thickness squared) of such thin interconnects is small, out-of-plane deformation commencing upon buckling significantly reduces the strain energy in metal interconnects.…”

“…Because of this irreversible deformation, the life-cycle of the stretchable supercapacitor array is expected to be much shorter than what is desirable for stretchable electronics ( ∼ 1000 cycles). Based on a commonly used criterion in finite element analysis validated by cyclic mechanical testing and four-probe resistance measurements [19][20][21][22], i.e. the maximum principal strain exceeding the yield strain in half of the width of an interconnect section, it was found that the reversible uniaxial stretchability of this supercapacitor array is only 8%.…”

Semi-liquid metal and adhesion-selection enabled rolling and transfer (SMART) printing: A general method towards fast fabrication of flexible electronics

“…At present, integrating inorganic or organic electronic materials with elastomeric substrates is the major approach to fabricate stretchable conductors. However, complicated and expensive fabrication and limited stretchability hinder the application of inorganic electronic materials [11][12][13][14][15]. The organic electronic materials own good stretchability, but their conductivities are lower than those of metal materials [16][17][18][19].…”