Enhancing the Sensitivity of Percolative Graphene Films for Flexible and Transparent Pressure Sensor Arrays

Abstract

Flexible and transparent pressure sensor arrays can find applications in many places such as touch panels, artificial skin, or human motion detection. However, conventional strain gauges are rigid and opaque and are not suitable for such applications. Graphene‐based percolative strain gauges can overcome these challenges but currently are still in the infancy of their development. In this work, the performance of graphene‐based percolative strain gauges is investigated and guidelines to improve the durability and sensitivity of graphene films as sensing elements are developed. It is found that the gauge factor depends on the initial resistance of the graphene film. For the same film resistance, it is found that graphene flake size and film morphology also play a role in determining the gauge factor. Increasing the flake–flake resistance through assembly of surfactant molecules between graphene flakes provides an additional route to enhance the gauge factor. Furthermore, encapsulating the percolative film in micrometer‐thin Poly(methyl methacrylate) does not disrupt the sensing process but significantly improves the sensor's durability. Finally, thus enhanced graphene strain gauges are integrated into flexible and transparent pressure sensor arrays that exhibit high reproducibility and sensitivity.

Highly Stretchable, Adaptable, and Durable Strain Sensing Based on a Bioinspired Dynamically Cross‐Linked Graphene/Polymer Composite

“…Conductive polymer composites that embed active elements or conductive fillers in or atop a soft polymer matrix can serve as excellent lightweight, low cost, readily processable strain sensing materials with high stretchability (measuring range) and sensitivity (gauge factor) . Various strategies have been developed to fabricate flexible strain sensors, including modulating aspect ratios, incorporation, orientation, and selective distribution, surface functionalization of active elements or conductive fillers . Among published examples, strain sensors based on graphene woven fabric structure and gold nanostructures have achieved extremely high sensitivity at small deformations.…”

Block copolymer structural color strain sensor

“…Numerous sensors have been demonstrated. The three major mechanical-to-electrical conversion principles are the capacitance [3][4][5][6][7][8] , piezo-electricity 9,10 , and piezoresistivity [11][12][13][14][15][16][17] . Piezo-based sensors rely upon either electrical voltage or resistance changes under mechanical deformation.…”

“…For instance, high-performance piezoresistivity in 1D or 2D nanomaterials with efficient pressure-sensitive percolation of their networked structures upon pressure application has been employed. This property gave rise to a high pressure sensitivity [12][13][14] . On the other hand, capacitive sensors utilize capacitance changes in pressure-sensitive dielectric films under mechanical stimuli.…”

Advanced carbon materials for flexible and wearable sensors

“…In particular, the selection of suitable active materials plays an important role in dominating the performance of sensors. To date, various materials, including carbon nanotubes (CNTs) [11,[26][27][28][29][30], graphene [31][32][33][34][35][36][37][38][39][40], carbon black [41][42][43][44][45], conductive polymers [16,[46][47][48], metal nanoparticles (NPs) and nanowires [21,[49][50][51][52][53][54][55], semiconductors [56,57], have been used as the active components for the fabrication of flexible sensors. Among these materials, metal NPs can be used to fabricate flexible sensors with high sensitivity, but the sensing range and stretchability of these sensors are limited [58].…”