Highly Elastic Graphene‐Based Electronics Toward Electronic Skin

Abstract

Epidermal electronics are extensively explored as an important platform for future biomedical engineering. Epidermal devices are typically fabricated using high‐cost methods employing complex vacuum microfabrication processes, limiting their widespread potential in wearable electronics. Here, a low‐cost, solution‐based approach using electroconductive reduced graphene oxide (RGO) sheets on elastic and porous poly(dimethylsiloxane) (PDMS) thin films for multifunctional, high‐performance, graphene‐based epidermal bioelectrodes and strain sensors is presented. These devices are fabricated employing simple coatings and direct patterning without using any complicated microfabrication processes. The graphene bioelectrodes show a superior stretchability (up to 150% strain), with mechanical durability up to 5000 cycles of stretching and releasing, and low sheet resistance (1.5 kΩ per square), and the graphene strain sensors exhibit a high sensitivity (a gauge factor of 7 to 173) with a wide sensing range (up to 40% strain). Fully functional applications of dry bioelectrodes in monitoring human electrophysiological signals (i.e., electrocardiogram, electroencephalography, and electromyogram) and highly sensitive strain sensors for precise detection of large‐scale human motions are demonstrated. It is believed that our unique processing capability and multifunctional device platform based on RGO/porous PDMS will pave the way for low‐cost processing and integration of 2D materials for future wearable electronic skin.

Graphene Nanostructure-Based Tactile Sensors for Electronic Skin Applications

“…In addition, their scalable production makes for an attractive choice for practical implementation [21]. Recently, researchers have developed several porous materials as templates to generate 3D graphene porous structures, such as polymer sponges (including polyurethane (PU) and polyvinyl chloride (PVC)) [73][74][75][76][77][78], various fabrics [79][80][81], cellulose paper [82], multilayer silk [83], all kinds of metal foams [84][85][86], and others [87][88][89].…”

“…b Real-time response of the MWNT-RGO@PU piezoresistive sensor for various small-scale motion monitoring applications was studied using the throat while pronouncing different words. Reproduced with permission from Ref [73]…”

Sugar transfer of nanomaterials and flexible electrodes

“…In flexible device application, patterning of large-scale 2D materials synthesized by chemical vapor deposition (CVD) is required [28][29][30]. We then corroborate that such sugar transfer application on patterned 2D materials, in which little quality decay is observed.…”

Highly flexible graphene nanoplatelet-polydimethylsiloxane strain sensors with proximity-sensing capability

“…Notably, the sensor conductivity remained almost unchanged after stretching, indicating that the GNP network sandwiched between PDMS is highly stable and robust and that the conductance recovery is fast and consistent even at a high frequency. Figure 4(b) summarizes the gauge factors and maximum stretchabilities of previously reported flexible strain sensors [5,14,[26][27][28][29][30][31][32][33][34][35][36][37][38][39]. As indicated by the dashed line, the gauge factor and stretchability have a trade-off.…”

“…(b) Summary of the gauge factors and maximum stretchability of the flexible strain sensors. The dashed line indicates the correlation between the gauge factor and the maximum stretchability, which exhibits a tradeoff relationship[5,14,[26][27][28][29][30][31][32][33][34][35][36][37][38].…”