Printable G‐Putty for Frequency‐ and Rate‐Independent, High‐Performance Strain Sensors

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 23; pp. e2006542 - n/a
• Main Authors: O'Driscoll, Daniel P., McMahon, Sean, Garcia, James, Biccai, Sonia, Gabbett, Cian, Kelly, Adam G., Barwich, Sebastian, Moebius, Matthias, Boland, Conor S., Coleman, Jonathan N.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-06-2021
• Subjects: Graphene; Hysteresis; Nanocomposites; Nanotechnology; percolation; piezoresistance; Polysiloxanes; pressure sensing; Sensitivity; Sensors; Strain rate; Substrates; Thin films; Viscoelasticity; pressure sensing; percolation; piezoresistance
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202006542

While nanocomposite electromechanical sensors are expected to display reasonable conductivity and high sensitivity, little consideration is given to eliminating hysteresis and strain rate/frequency dependence from their response. For example, while G‐putty, a composite of graphene and polysiloxane, has very high electromechanical sensitivity, its extreme viscoelasticity renders it completely unsuitable for real sensors due to hysteretic and rate‐/frequency‐dependent effects. Here it is shown that G‐putty can be converted to an ink and printed into patterned thin films on elastic substrates. A partial graphene‐polymer phase segregation during printing increases the thin‐film conductivity by ×106 compared to bulk, while the mechanical effects of the substrate largely suppress hysteresis and completely remove strain rate and frequency dependence. This allows the fabrication of practical, high‐gauge‐factor, wearable sensors for pulse measurements as well as patterned sensors for low‐signal vibration sensing.
Here the production of a range of graphene/polysiloxane/solvent inks, which can be used to print‐patterned, conductive, thin films, is described. These films have high piezoresistive gauge factors and can be used to fabricate highly sensitive strain sensors with good frequency independence and low hysteresis.