Bean Pod-Inspired Ultrasensitive and Self-Healing Pressure Sensor Based on Laser-Induced Graphene and Polystyrene Microsphere Sandwiched Structure

Abstract

Flexible pressure sensors are currently at the center stage of wearable electronics. Despite tremendous progress in the recent years, flexible pressure sensors with high sensitivity, high stability, and mechanical robustness are still challenging. In this paper, as inspired by the bean pod structure, a sensor architecture consisting a microspacer core layer of polystyrene (PS) microspheres, sandwiched between two laser-induced graphene/polyurethane (LIG/PU) films, is presented. A flexible and self-healable pressure sensor is prepared, achieving ultrahigh sensitivity, improved linearity, wide sensing range up to 100 kPa, and excellent stability (for over 1000 loading−unloading cycles). Specifically, the pressure sensor achieves high sensitivities of 149, 659, and 2048 kPa −1 for the pressure ranges of 0−1, 1−10, and 10−100 kPa, respectively. Upon three cut−heal cycles at room temperature, severely damaged devices are self-healed and are able to maintain high sensitivity. The sensors have been further verified in stringent applications, such as human arterial pulse monitoring and gait detection. The novel device architecture enabling facile fabrication and high performance paves the way to the scalable production of pressure sensors for human physiological diagnostics and other advanced wearable applications.

Microengineering Pressure Sensor Active Layers for Improved Performance

“…An alternative method of microengineering the active layer of resistive pressure sensors to improve performance is to introduce micropores. [ 44,87,112–114 ] Using FEM to simulate samples with different pore sizes, Kim et al found that modulus changes based on pore size and pore density. [ 87 ] Further, Visser et al found that modulus changes whether the overall structure is open‐cell or closed‐cell (Figure 9A).…”

Physical Sensors Based on Laser-Induced Graphene: A Review

“…Piezoresistive transducers. The piezoresistance of LIG electrodes printed on flexible PI films has been exploited and utilized in a range of configurations, including measurements of strain, deflection, curvature, force, and pressure [86,89,90,94,97,103,105]. The high variation of the electrical resistance of multilayer samples under strain is induced by the displacement of the layers and changes of their overlapping area.…”

Bioinspired Design of Graphene‐Based Materials

“…Adapted with permission. [174] Copyright 2020, American Chemical Society; e) SEM images of different parts of a printed synthetic spider's web. Adapted with permission.…”

“…For instance, a bean pod-like configuration, where the "pod" is a conductive porous graphene network and the "beans" are insulating polymer spacers (Figure 9d), results in a good pressure-sensing behavior in both high-and low-pressure regimes because the conductance changes significantly as the spacers are compressed. [174] At the same time, the geometry can be tuned to provide spatial resolution. In a spider web, the radial threads, which provide structural support and transport vibrational signals, have a different structure to the flexible spiral threads, where prey is caught.…”