Specimen size effect on the fracture energy of architected stretchable materials

Architected stretchable materials with well-organized microarchitectures evolve very rapidly due to their potential in customizing mechanical properties and achieving exotic functions.In many applications,the architected stretchable materials are required to sustain large deformation,and their fracture is size-dependent.However,the size effect on the fracture of architected stretchable materials is still elusive.Here,we study this issue by experiment and finite element calculation.It is found that the fracture energy of architected stretchable materials increases with the specimen size ratio,H/h,within a range.When H/h reaches a transition ratio,Rt,the fracture energy approaches a plateau.This transition ratio differentiates the size-dependent and size-independent fracture behavior of architected stretchable materials.The mechanical properties of constituent material only have a minor effect on the transition ratio.The degree of constraint and stress concentration at the node,which are affected by the geometry of the unit-cell,dominate the specimen size effect.The result gives a practical guidance in choosing the specimen size to measure the steady state fracture energy of this class of materials.This work provides insights into the fracture of architected stretchable materials and design for fractureresistant architected stretchable devices.

A Comprehensive Review of Wearable Applications and Material Construction

Wearable electronic systems are able to monitor and measure multiple biophysical, biochemical signals to help researchers develop further understandings of human health and correlation between human performance and diseases. Driven by increasing demand for need in sports training, health monitoring and disease diagnose, bio-integrated systems are developing at a significant speed based on recent advances in material science, structure design and chemical techniques. A wide range of wearable systems are created and feature unique measuring targets, methods and soft, transparent, stretchable characters. This review summarizes the recent advances in wearable electronic technologies that also include material science, chemical science and electronic engineering. The introduction to basic wearable fundamentals covers subsequent consideration for materials, system integration and promising platforms. Detailed classification towards their functions of physical, chemical detection is also mentioned. Strategies to achieve stretchability and promising material, AgNW, are fully discussed. This paper concludes with consideration of main challenging obstacles in this emerging filed and promises in materials that possess excellent potentials for predicted progress.