Localized modulus-controlled PDMS substrate for 2D and 3D stretchable electronics

Stretchable electronics have great importance for applications of wearable devices and electronic skin. Balancing and improving mechanical stretchability and electronic performance are the key challenges that restrict further development of stretchable electronics. In order to achieve stretchable electronics, it is crucial to choose appropriate substrates, among which PDMS is the most commonly used polymer due to its easy fabrication and low cost. In this paper, we propose a novel strategy and fabricate localized modulus-controlled PDMS for both 2D and 3D stretchable electronics. Based on a secondary cross-link effect, the modulus of cured PDMS can be enhanced and controlled by spin-coating different masses of curing agent. Using a laser-cut PI mask, the modulus-enhanced region can be defined by users. Through this simple method, the functional conductive thin-film materials (gold/Ag nanowires/reduced graphene oxide) can be well protected when the structural layer is stretched and the 'barrel effect' of a multi-material film (where different material films possess different stretchability) on one piece of substrate can also be solved. Besides this, compared with uniform PDMS, different 3D buckling structures can be formed on locally modified PDMS as a substrate by a pre-stretching and releasing process, illustrating a new way to control the 3D buckling structure. © 2020 IOP Publishing Ltd.