Ultra-Conformable Free-Standing Capacitors Based on Ultrathin Polyvinyl Formal Films

TL;DR

This paper introduces a novel ultra-thin, free-standing polyvinyl formal capacitor that is highly conformable, capable of adhering to complex surfaces, and represents the thinnest free-standing capacitor reported to date.

Contribution

The work presents a new fabrication method for ultrathin, free-standing capacitors using polyvinyl formal nanosheets, achieving unprecedented thinness and conformability.

Findings

Capacitors with thickness as low as 200 nm were fabricated.

The capacitors can conform to surfaces with curvature radii as small as 1.5 μm.

They can adhere to complex textured surfaces without losing functionality.

Abstract

Conformable Electronics refers to a class of electronic devices that have the ability to conformally adhere onto non-planar surfaces and materials, resulting particularly appealing for skin applications, such as the case of skin-worn unobtrusive (bio)sensors for healthcare monitoring. Conformability can be addressed by integrating basic electronic components on ultrathin polymeric film substrates. Among other basic electronic components, capacitors are fundamental ones for energy storage, sensing, frequency tuning, impedance adaptation and signal processing. In this work we present a novel approach for conformable capacitors based on a free-standing, ultrathin and ultra-conformable nanosheets of poly (vinyl formal) (PVF), which serve both as structural and dielectric component of the capacitor. A novel fabrication approach is proposed and applied to fully free-standing ultrathin capacitors fabrication, having an overall thickness as low as 200 nm; that represents, to the best of our knowledge, the thinnest free-standing capacitors ever reported. Thanks to the ultra-low thickness, the proposed capacitors are able to sustain flexure to extremely small curvature radii (as low as 1.5 {\mu}m) and to conform to complex surfaces, such as a nylon mesh with micrometric texture without compromising their operation.