Design strategy of porous elastomer substrate and encapsulation forinorganic stretchableelectronics

The emergence of stretchable electronic technology has led to the development of many industries and facilitated many unprecedented applications,owing to its ability to bear var-ious deformations.However,conventional solid elastomer sub-strates and encapsulation can severely restrict the free motion and deformation of patterned interconnects,leading to poten-tial mechanical failures and electrical breakdowns.To address this issue,we propose a design strategy of porous elastomer substrate and encapsulation to improve the stretchability of serpentine interconnects in island-bridge structures.The ser-pentine interconnects are fully bonded to the elastomer sub-strate,while segments above circular pores remain suspended,allowing for free deformation and a substantial improvement in elastic stretchability compared to the solid substrates.The pores ensure unimpeded interconnect deformations,and mod-erate porosity provides support while maintaining the initial planar state.Compared to conventional solid configurations,finite element analysis(FEA)demonstrates a substantial enhancement of elastic stretchability(e.g.=9 times without encapsulation and=7 times with encapsulation).Uniaxial cyc-lic loading fatigue experiments validate the enhanced elastic stretchability,indicating the mechanical stability of the porous design.With its intrinsic advantages in permeability,the pro-posed strategy has the potential to offer insightful inspiration and novel concepts for advancing the field of stretchable inorganic electronics.

Morphable three-dimensional electronic mesofliers capable of on-demand unfolding

Development of miniaturized three-dimensional(3 D)fliers with integrated functional components has important implications to a diverse range of engineering areas.Among the various active and passive miniaturized 3 D fliers reported previously,a class of 3 D electronic fliers inspired by wind-dispersed seeds show promising potentials,owing to the lightweight and noiseless features,aside from the stable rotational fall associated with a low falling velocity.While on-demand shape-morphing capabilities are essential for those 3 D electronic fliers,the realization of such miniaturized systems remains very challenging,due to the lack of fast-response 3 D actuators that can be seamlessly integrated with 3 D electronic fliers.Here we develop a type of morphable3 D mesofliers with shape memory polymer(SMP)-based electrothermal actuators,capable of large degree of actuation deformations,with a fast response(e.g.,~1 s).Integration of functional components,including sensors,controllers,and chip batteries,enables development of intelligent 3 D mesoflier systems that can achieve the on-demand unfolding,triggered by the processing of real-time sensed information(e.g.,acceleration and humidity data).Such intelligent electronic mesofliers are capable of both the low-air-drag rising and the low-velocity falling,and thereby,can be used to measure the humidity fields in a wide 3 D space by simple hand throwing,according to our demonstrations.The developed electronic mesofliers can also be integrated with other types of physical/chemical sensors for uses in different application scenarios.

Recent progress in three-dimensional flexible physical sensors

Three-dimensional(3D)functional systems are of rapidly growing interest over the past decade,from the perspective of both the fundamental and applied research.In particular,tremendous efforts have been devoted to the developments of 3D flexible,physical sensors,partly because of their substantial advantages over planar counterparts in many specific performances.In this review,we summarize recent advances in diverse categories of 3D flexible physical sensors,covering the photoelectric,mechanical,temperature,magnetic,and other physical sensors.This review mainly focuses on their design strategies,working principles and applications.Finally,we offer an outlook on the future developments,and provide perspectives on the remaining challenges and opportunities in this area.

Engineering in-plane silicon nanowire springs for highly stretchable electronics

Crystalline silicon（c-Si） is unambiguously the most important semiconductor that underpins the development of modern microelectronics and optoelectronics, though the rigid and brittle nature of bulk c-Si makes it difficult to implement directly for stretchable applications. Fortunately, the one-dimensional（1 D） geometry, or the line-shape, of Si nanowire（SiNW） can be engineered into elastic springs, which indicates an exciting opportunity to fabricate highly stretchable 1 D c-Si channels. The implementation of such line-shape-engineering strategy demands both a tiny diameter of the SiNWs, in order to accommodate the strains under large stretching, and a precise growth location, orientation and path control to facilitate device integration. In this review, we will first introduce the recent progresses of an in-plane self-assembly growth of SiNW springs, via a new in-plane solid-liquidsolid（IPSLS） mechanism, where mono-like but elastic SiNW springs are produced by surface-running metal droplets that absorb amorphous Si thin film as precursor. Then, the critical growth control and engineering parameters, the mechanical properties of the SiNW springs and the prospects of developing c-Si based stretchable electronics, will be addressed. This efficient line-shape-engineering strategy of SiNW springs, accomplished via a low temperature batch-manufacturing, holds a strong promise to extend the legend of modern Si technology into the emerging stretchable electronic applications, where the high carrier mobility, excellent stability and established doping and passivation controls of c-Si can be well inherited.