Wearable multifunctional printed graphene sensors

Altynay Kaidarova,Ulrich Buttner,Cobus Muller,Jurgen Kosel,Alexander Przybysz,Nathan R Geraldi,Rory P Wilson,Marco Marengo,Mohammed Asadullah Khan,Carlos M Duarte,Liam Swanepoel,Andreas Fahlman

doi:10.1038/s41528-019-0061-5

Abstract

The outstanding properties of graphene have initiated myriads of research and development; yet, its economic impact is hampered by the difficulties encountered in production and practical application. Recently discovered laser-induced graphene is generated by a simple printing process on flexible and lightweight polyimide films. Exploiting the electrical features and mechanical pliability of LIG on polyimide, we developed wearable resistive bending sensors that pave the way for many cost-effective measurement systems. The versatile sensors we describe can be utilized in a wide range of configurations, including measurement of force, deflection, and curvature. The deflection induced by different forces and speeds is effectively sensed through a resistance measurement, exploiting the piezoresistance of the printed graphene electrodes. The LIG sensors possess an outstanding range for strain measurements reaching >10% A double-sided electrode concept was developed by printing the same electrodes on both sides of the film and employing difference measurements. This provided a large bidirectional bending response combined with temperature compensation. Versatility in geometry and a simple fabrication process enable the detection of a wide range of flow speeds, forces, and deflections. The sensor response can be easily tuned by geometrical parameters of the bending sensors and the LIG electrodes. As a wearable device, LIG bending sensors were used for tracking body movements. For underwater operation, PDMS-coated LIG bending sensors were integrated with ultra-low power aquatic tags and utilized in underwater animal speed monitoring applications, and a recording of the surface current velocity on a coral reef in the Red Sea.

Highlights

Bending sensors provide an electrical signal as a function of the bending radius or curvature.[1]
In case of passive resistive bending sensors, an electrically conductive pattern or electrode is fabricated on top of a flexible substrate, and changes its resistance upon substrate bending
In 2014, it was discovered that direct lasing of PI films leads to the formation of 3D porous graphene,[32,33,34] by a photothermal process associated with a localized high temperature, the pressure produced by laser irradiation and easy absorption of longwavelength radiation

Summary

INTRODUCTION

Bending sensors provide an electrical signal as a function of the bending radius or curvature.[1] Such sensors offer an extremely versatile sensing platform capable of measuring changes of various physical quantities They can be made lightweight, lowcost, and robust and tolerate vibration, thermal shock and stretching without electromagnetic interference or sensor occlusion.[2] The application areas of bending sensors are rapidly increasing, including medical,[3,4] automotive,[5] industrial,[6,7] physical activity measurements,[6,8] and human–machine interactions.[9] In case of passive resistive bending sensors, an electrically conductive pattern or electrode is fabricated on top of a flexible substrate, and changes its resistance upon substrate bending. In 2014, it was discovered that direct lasing of PI films leads to the formation of 3D porous graphene,[32,33,34] by a photothermal process associated with a localized high temperature, the pressure produced by laser irradiation and easy absorption of longwavelength radiation This process enables the development of LIG bending sensors that are mechanically flexible, lightweight, robust, and multifunctional. The flow tube for sensor testing was assembled using two segments of opaque PVC (0.73 -m length)

Kaidarova et al 4

Findings

METHODS