Switchable dry adhesive based on shape memory polymer with hemispherical indenters for transfer printing

Transfer printing based on switchable adhesive is essential for developing unconventional systems,including flexible electronics,stretchable electronics,and micro light-emitting diode(LED)displays.Here we report a design of switchable dry adhesive based on shape memory polymer(SMP)with hemispherical indenters,which offers a continuously tunable and reversible adhesion through the combination of the preloading effect and the thermal actuation of SMP.Experimental and numerical studies reveal the fundamental aspects of design,fabrication,and operation of the switchable dry adhesive.Demonstrations of this adhesive concept in transfer printing of flat objects(e.g.,silicon wafers),three-dimensional(3D)objects(e.g.,stainless steel balls),and rough objects(e.g.,frosted glasses)in two-dimensional(2D)or 3D layouts illustrate its unusual manipulation capabilities in heterogeneous material integration applications.

Fully paper-integrated hydrophobic and air permeable piezoresistive sensors for high-humidity and underwater wearable motion monitoring

Paper-based electronics have attracted much attention due to their softness,degradability,and low cost.However,paper-based sensors are difficult to apply to high-humidity environments or even underwater.Here,we report a fully paper-integrated piezoresistive sensing system that exhibits flexibility,waterproofing,air permeability,and biocompatibility.This system consists of hydrophobic paper as the substrate and encapsulation layer,conductive paper with a double‘zig-zag’and dotted surface structure as the sensing layer,and silver paste films as the interconnects.The structural design of the sensing layer helps to increase the contact area in adjacent layers under pressure and further improves the pressure sensitivity.The piezoresistive system can be worn on human skin in the ambient environment,wet environment,and water for real-time monitoring of physiological signals with air permeability and waterproofing due to its hydrophobic fiber structure.Such a device provides a reliable,economical,and ecofriendly solution to wearable technologies.

Stretchable,Rehealable,Recyclable,and Reconfigurable Integrated Strain Sensor for Joint Motion and Respiration Monitoring

Cutting-edge technologies of stretchable,skin-mountable,and wearable electronics have attracted tremendous attention recently due to their very wide applications and promising performances.One direction of particular interest is to investigate novel properties in stretchable electronics by exploring multifunctional materials.Here,we report an integrated strain sensing system that is highly stretchable,rehealable,fully recyclable,and reconfigurable.This system consists of dynamic covalent thermoset polyimine as the moldable substrate and encapsulation,eutectic liquid metal alloy as the strain sensing unit and interconnects,and off-the-shelf chip components for measuring and magnifying functions.The device can be attached on different parts of the human body for accurately monitoring joint motion and respiration.Such a strain sensing system provides a reliable,economical,and ecofriendly solution to wearable technologies,with wide applications in health care,prosthetics,robotics,and biomedical devices.