Skin-like electronics allow seamless integration with the human body to provide continuous, high-fidelity monitoring of physiological signals for real-time health analysis, localized treatment and enhanced sensorimotor functions in prosthetics and augmented reality applications. Functional materials and devices that are intrinsically stretchable and capable of maintaining intimate contact with dynamic, moving tissues are highly sought after. Despite substantial progress in material innovation and device engineering, having a large integration scale alongside superior electrical performance is still a challenge.
The building blocks of the system are bottom-gated transistors. First, spin-coated poly(3,4-ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS) was patterned as the gate electrode with a surface roughness of 1.3 nm. The PEDOT:PSS dispersion was cross-linked using a topological supramolecular crosslinker (based on polyrotaxnes) to enhance the stretchability of the film without compromising its conductivity. A nitrile-butadiene dielectric with a dielectric constant of 10 at 100 kHz, was then photopatterned using a direct process based on a thiol-ene reaction and passivated using a 50-nm styrene-ethylene-butylene-styrene elastomeric film. A metal-assisted lift-off of a stacked structure of poly(methyl methacrylate)/copper/spray-coated metallic-carbon nanotubes/palladium was introduced for patterning the source-drain electrodes. Thanks to the sharp edges created by the metal-layer-assisted lift-off, channel lengths of 0.9 µm were achieved. Moreover, the presence of the palladium layer reduced the contact resistance by about 80%. Semiconducting carbon nanotube networks were chosen as channel material for their charge-carrier mobilities. To address hysteresis issues in transfer curves caused by oxygen plasma treatment of the polymer dielectric, semiconducting carbon nanotubes were first deposited onto a dextran film before being transferred onto the polymer dielectric. Finally, a film of styrene–butadiene–styrene was deposited as an encapsulation layer and EGaIn electrodes as global interconnects (with a sheet resistance of about 0.2 Ω sq−1).
This is a preview of subscription content, access via your institution