As performant and well-established as conventional silicon-based electronics have become, the era of wearable electronics and the Internet-of-Things has created a demand for robust electronic devices that can conform to the surfaces of the human body. Whereas the mechanical mismatch between rigid silicon electronics and the human body represents a fundamental limit to conventional non-invasive health sensing, wearable electronics and electrodes that can conform to the microscopic features of the skin^1,2 can circumvent most of the motion artifacts inherent to conventional, rigid sensing devices, and facilitate continuous health monitoring as is required for modern, more proactive healthcare. Unfortunately, without addressing this fundamental mechanical incompatibility, devices that leverage the high density of transistors available in rigid silicon-based integrated circuits are handicapped by how well they can maintain contact with the body, and consequently are prone to failure at the sensor-circuit interface.

The extraordinary properties of two-dimensional materials pose a unique opportunity for addressing this mechanical mismatch. Their unusual mechanical strength combined with their ultimate thinness, optical transparency, and favorable electronic transport properties³ makes them ideal candidates for the next generation of highly conformable wearable electronics free of the constraints of a rigid silicon circuit board—however, minimizing local strain in the vicinity of the active devices to ensure reliable operation remains a priority. Using a design informed by finite element method (FEM) simulations, our proposed strain-neutralizing 2D transistors are configured to resist applied strains on the order of the 30% strains human skin can withstand by redistributing strain away from active regions. Tight binding simulations of the transistor channels helps with further compensation of residual strain in the active regions, alongside careful consideration of materials and device architecture during fabrication. Together, these considerations help realize the possibility of fully integrated strain-neutralized 2D transistors compatible with state-of-the-art conformable wearable sensors.

[1]S. Kabiri Ameri et al., “Graphene electronic tattoo sensors,” ACS Nano, 11, 7634–7641, 2017.

[2] S. Kabiri Ameri et al., “Imperceptible electrooculography graphene sensor system for human–robot interface”, npj 2D Materials and Applications, 2, 1-7, 2018.

[3] A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K. Geim, “The electronic properties of graphene,” Rev. Mod. Phys., vol. 81, no. 1, pp. 109–162, Jan. 2009, doi: 10.1103/RevModPhys.81.109.