Toothed Substrate Design to Improve Stretchability of Serpentine Interconnect for Stretchable Electronics

Abstract

and eye-like digital cameras [15,16] ) with biological tissues without mechanically induced irritation. [17][18][19][20] A challenge of the flexible and stretchable electronics is to accommodate large deformations of biological tissues. [7,[21][22][23] One of the solutions to address this challenge involves the development of organic semiconductor materials that have high fracture strains. [24][25][26] Alternatives rely on structure designs to achieve high stretchability, [27][28][29][30] such as the integration of serpentine interconnects and inorganic functional materials with a soft elastomeric substrate. [31][32][33][34][35] A disadvantage of such integrated system is that the serpentine interconnects are bonded to the elastomeric substrate, which constraints the free buckling of the serpentine interconnects and therefore limits the stretchability of the devices. [36][37][38] Many designs were proposed to reduce the constraints of the elastomeric substrate on the serpentine interconnect to improve the stretchability, e.g., microfluidic assemblies, [21,39] core/shell packages, [40] and patterned substrate. [41,42] The preparation process of the patterned substrate is the simplest among these approaches. However, the major challenge to exploit patterned substrates is to precisely position the serpentine interconnects on the patterned substrates. The stretchability of the integrated systems depends on the alignment and position between the serpentine interconnects and patterned substrates, which has great randomness. [43] In this paper, an integrated system combining serpentine interconnects with toothed substrates is proposed to improve the stretchability of the serpentine interconnects bonded to conventional planar substrates. Here, the straight segments of the serpentine interconnects are bonded to the teeth molds of the toothed substrates as shown in Figure 1e. The arc segments (maximum strain area) of the serpentine interconnects are freestanding in this design so that it can provide high stretchability for the system. Furthermore, slight translation between the serpentine interconnects and toothed substrates changes little of the freestanding dimension of the arc segments. Therefore, such an integrated system also solves the challenge of uncontrolled stretchability for traditional patterned substrates. Systematic studies include results from quantitative experiments and comparisons with analytical models and finite element method computations. These studies have general utility for future work on stretchability design for flexible and stretchable electronics.Integration of deformable serpentine interconnects and inorganic functional materials with soft elastomeric substrate enables the electronics to deform into arbitrary desired shapes. Conventionally, the serpentine interconnects are bonded to a planar substrate, which limits the out-of-plane buckling of the serpentine interconnects, and thus restricts their stretchability. An integrated system combining serpentine interconnects with toothed substrate is...

Transfer printing technologies for soft electronics

“…Yet, due to the restriction of out-of-plane deformation for the stretchable serpentine interconnects, soft elastomer-based packing materials could highly influence the system stretchability, especially for 3D integrated electronics. 113,114 Honglie Song et al used a polyimide network material (Fig. 5c) as a constraint-free platform and a 3D integrated soft system with high areal coverage (∼110%) was developed (Fig.…”

Flexible and Stretchable Antennas for Biointegrated Electronics

“…The development of soft, biointegrated technology platforms depends critically on enabling materials for ultrathin, ultralow modulus devices that can undergo large mechanical deformations. [68] A widely used design strategy involves thin, filamentary serpentine structures as interconnects and/or supporting platforms for electronic elements that embed within thin, soft elastomeric films, [37,38,69,70] as a type of composite material structure that combines the electrical properties of inorganic electronic systems with the mechanical properties of elastomeric polymers. In optimized layouts, these systems allow stretching, bending, and twisting deformations for seamless, conformal integration onto curvilinear surfaces of soft biological tissues, while maintaining high-performance operation.…”

Highly Stretchable Bilayer Lattice Structures That Elongate via In‐Plane Deformation

“…Integration of such stretchable structures into electronic devices usually relies on intricate device designs (such as patterned substrate) with prereserved spaces to accommodate the out-of-plane features, increasing the complexity of the fabrication process. [4] More importantly, surfaces with these out-of-plane features are uneven and nonsmooth, which gives rise to high surface roughness, [21] poor adhesion, [22] and low optical transmittance. [23] The advent of modern additive manufacturing techniques such as 3D printing offers rapid prototyping and demonstrate potent capability in printing a broad range of materials into complex structures, thereby opening new opportunities to manufacture novel engineering structures.…”

“…The first one relies on introducing serpentineshaped patterns to otherwise unstretchable structures. [4][5][6][7] These designed structures are initially planar and consist of serpentine patterns in their plane. When being stretched, the structures made of serpentine patterns can deflect and twist out of the plane, aligning to the direction of the applied loading largely by rigid-body rotation, giving rise to substantially enhanced stretch capability.…”