Universal modulus-free transfer of scalable laser-induced graphene for electronic skins.

Electronic skin (E-skin) with multifunctionality and large-scale features is highly desirable for human-machine interactions and wearable health monitoring. Laser-induced graphene (LIG) affords such devices with tailorable physical and chemical properties. However, relatively high Young's modulus of precursors that derive LIG hinders its application scenarios. Here, we report a universal cryogenic transfer approach for LIG via regulating the glass transition temperature or freezing point of the transfer media. The thermal expansion-induced interlocking, ease of interfacial separation and strong electrostatic interactions within the multiple graphene layers explain the transfer mechanisms. This contributes to the high-quality transfer of LIG onto elastomers, hydrogels and fabrics infused with various fluids. The thickness of typical elastomer can be down to 6.7 μm with its Young's modulus ranging from 4.5 MPa to 3.9 kPa. Using this transfer technique, we create large-scale and double-layer E-skins integrated on a humanoid robot face, achieving emotional interactions with humans. The proposed strategy for merging LIG with broad categories of media affords on-demand designs of wearable and implantable electronics.