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.

A thermal actuated switchable dry adhesive with high reversibility for transfer printing

Transfer printing based on switchable adhesive that heterogeneously integrates materials is essential to develop novel electronic systems,such as flexible electronics and micro LED displays.Here,we report a robust design of a thermal actuated switchable dry adhesive,which features a stiff sphere embedded in a thermally responsive shape memory polymer(SMP)substrate and encapsulated by an elastomeric membrane.This construct bypasses the unfavorable micro-and nano-fabrication processes and yields an adhesion switchability of over1000 by combining the peel-rate dependent effect of the elastomeric membrane and the thermal actuation of the sub-surface embedded stiff sphere.Experimental and numerical studies reveal the underlying thermal actuated mechanism and provide insights into the design and operation of the switchable adhesive.Demonstrations of this concept in stamps for transfer printing of fragile objects,such as silicon wafers,silicon chips,and inorganic micro-LED chips,onto challenging non-adhesive surfaces illustrate its potential in heterogeneous material integration applications,such as flexible electronics manufacturing and deterministic assembly.

Implantable Thermal Therapeutic Device with Precise Temperature Control Enabled by Foldable Electronics and Heat-Insulating Pads

Thermal therapy has continued to attract the attention of researchers and clinicians due to its important applications in tumor ablation,wound management,and drug release.The lack of precise temperature control capability in traditional thermal treatment may cause the decrease of therapeutic effect and thermal damage to normal tissues.Here,we report an implantable thermal therapeutic device(ITTD),which offers precise closed loop heating,in situ temperature monitoring,and thermal protection.The ITTD features a multifunctional foldable electronics device wrapped on a heat-insulating composite pad.Experimental and numerical studies reveal the fundamental aspects of the design,fabrication,and operation of the ITTD.In vivo experiments of the ITTD in thermal ablation for antitumor demonstrate that the proposed ITTD is capable of controlling the ablation temperature precisely in real time with a precision of at least 0.7℃ and providing effective thermal protection to normal tissues.This proof-of-concept research creates a promising route to develop ITTD with precise temperature control capability,which is highly desired in thermal therapy and other disease diagnosis and treatments.

Soft,stretchable thermal protective substrates for wearable electronics

Wearable electronics have continued to attract the attention of researchers and clinicians due to their great potential in medical applications.During their operations,the undesired heating may cause thermal discomfort or damage to skin.Seeking materials and structures for advanced thermal protection has become an urgent issue.Here,we report a soft,stretchable thermal protective substrate for wearable electronics with remarkable thermal insulating performance,mechanical compliance and stretchability.The thermal protective substrate features a composite design of the widely used polymeric material polydimethylsiloxane with embedded heat absorbing microspheres,consisting of phase change materials encapsulated inside the resin shell.Experimental and numerical studies show that the thermal protective substrate could be subjected to complex deformations over 150% and could reduce the peak skin temperature increase by 82% or higher under optimizations.In vivo demonstration of this concept on the mouse skin illustrates its unusual thermal protection capability for wearable thermal management.