Wearable multifunctional printed graphene sensors

The outstanding properties of graphene have initiated myriads of research and development;yet, its economic impact is hamperedby the difficulties encountered in production and practical application. Recently discovered laser-induced graphene is generated bya simple printing process on flexible and lightweight polyimide films. Exploiting the electrical features and mechanical pliability ofLIG on polyimide, we developed wearable resistive bending sensors that pave the way for many cost-effective measurementsystems. 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 resistancemeasurement, exploiting the piezoresistance of the printed graphene electrodes. The LIG sensors possess an outstanding range forstrain measurements reaching >10% A double-sided electrode concept was developed by printing the same electrodes on bothsides of the film and employing difference measurements. This provided a large bidirectional bending response combined withtemperature compensation. Versatility in geometry and a simple fabrication process enable the detection of a wide range of flowspeeds, forces, and deflections. The sensor response can be easily tuned by geometrical parameters of the bending sensors and theLIG 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 speedmonitoring applications, and a recording of the surface current velocity on a coral reef in the Red Sea.

Flexible Hall sensor made of laser-scribed graphene

Graphene has shown considerable potential for sensing magnetic fields based on the Hall Effect,due to its high carrier mobility,low sheet carrier density,and low-temperature dependence.However,the cost of graphene in comparison to conventional materials has meant that its uptake in electronic manufacturing has been slow.To lower technological barriers and bring more widespread adoption of graphene Hall sensors,we are using a one-step laser scribing process that does not rely on multiple steps,toxic chemicals,and subsequent treatments.Laser-scribed graphene Hall sensors offer a linear response to magnetic fields with a normalized sensitivity of~1.12 V/AT.They also exhibit a low constant noise voltage floor of~50 nV√Hz p for a bias current of 100μA at room temperature,which is comparable with state-of-the-art low-noise Hall sensors.The sensors combine a high bendability,come with high robustness and operating temperatures up to 400°C.They enable device ideas in various areas,for instance,soft robotics.As an example,we combined a laser-scribed graphene sensor with a deformable elastomer and flexible magnet to realize low-cost,compliant,and customizable tactile sensors.