Multiscale porous elastomer substrates for multifunctional on-skin electronics with passive-cooling capabilities

Abstract

In addition to mechanical compliance, achieving the full potential of on-skin electronics needs the introduction of other features. For example, substantial progress has been achieved in creating biodegradable, self-healing, or breathable, on-skin electronics. However, the research of making on-skin electronics with passive-cooling capabilities, which can reduce energy consumption and improve user comfort, is still rare. Herein, we report the development of multifunctional on-skin electronics, which can passively cool human bodies without needing any energy consumption. This property is inherited from multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) supporting substrates. The multiscale pores of SEBS substrates, with characteristic sizes ranging from around 0.2 to 7 µm, can effectively backscatter sunlight to minimize heat absorption but are too small to reflect human-body midinfrared radiation to retain heat dissipation, thereby delivering around 6 °C cooling effects under a solar intensity of 840 W⋅m−2. Other desired properties, rooted in multiscale porous SEBS substrates, include high breathability and outstanding waterproofing. The proof-of-concept bioelectronic devices include electrophysiological sensors, temperature sensors, hydration sensors, pressure sensors, and electrical stimulators, which are made via spray printing of silver nanowires on multiscale porous SEBS substrates. The devices show comparable electrical performances with conventional, rigid, nonporous ones. Also, their applications in cuffless blood pressure measurement, interactive virtual reality, and human–machine interface are demonstrated. Notably, the enabled on-skin devices are dissolvable in several organic solvents and can be recycled to reduce electronic waste and manufacturing cost. Such on-skin electronics can serve as the basis for future multifunctional smart textiles with passive-cooling functionalities.

Skin Impedance Measurements with Nanomesh Electrodes for Monitoring Skin Hydration

“…For example, high water vapor permeability is achieved by processing the electrodes into a suitable porous shape or by fabricating electrodes on a porous substrate. [ 16‐21 ] Since these electrodes are less likely to inhibit water evaporation from skin, it is expected that measurements could be performed in a nearly natural state without causing skin dampness by wearing them. In addition, there are reports on electrodes that use highly biocompatible materials such as poly‐vinyl‐alcohol (PVA), [ 18,21 ] gels, [ 22 ] and silk fibroin for biocompatibility.…”

Materials, Devices, and Systems of On‐Skin Electrodes for Electrophysiological Monitoring and Human–Machine Interfaces

“…also proposed a phase separation‐controlled synthesis method to prepare multiscale porous electrode substrate. [ 13 ] During this process, polystyrene‐ block ‐poly(ethylene‐ran‐butylene)‐ block ‐polystyrene (SEBS) and isopropyl alcohol (IPA) were mixed into chloroform to fabricate the precursor solution. Subsequently, the precursor was coated on an aluminum foil and dried in ambience.…”

“…[ 9,10 ] As an index of the initiation and fatigue of activated muscles, EMG signals originate from electrical activities produced by muscle of interest and are suitable for monitoring muscular diseases and mental fatigue etc. [ 11 ] Particularly, the characteristics of EMG signals from muscles on forearm can be directly correlated to hand gestures, [ 12 ] therefore, EMG signals are widely used for gesture recognition, [ 13 ] prosthetic control, [ 14 ] etc. EEG signals obtained from human scalp surface capture the post‐synaptic potentials generated by pyramidal neurons, [ 15 ] thus can be utilized to assist brain‐activity cognition and mental disease diagnosis, such as epilepsy diagnoses.…”

Thermal management of wearable and implantable electronic healthcare devices: Perspective and measurement approach

“…118 Prasher et al found an optimal volume fraction for a given pressure and filler shape. 115 Xu et al 119 introduced a substrate, namely, multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-blockpolystyrene (SEBS), to support the cooling effect. They developed multifunctional on-skin electronics with improved passive cooling capability that can deliver 6 C of cooling effects under a solar intensity of 840 W.m −2 .…”