Environment-Resilient Graphene Vibrotactile Sensitive Sensors for Machine Intelligence

Abstract

Skin-like sensors that transduce tactile pressures and vibrations with minimal environment variation on performance are crucial in robotic sensing and prosthetic skins. However, sensor performance variations under varying environmental conditions, such as temperature and humidity, are common in piezoresistive sensors because of their intrinsic materials properties. Moreover, the viscoelasticity of soft elastomers causes strain response in a time-dependent fashion, which poses sensor limitations in high-frequency tactile tasks, such as texture recognition. In this work, we demonstrate a new environment-robust tactile sensor via an interfacial engineering process for uniform graphene coating on microstructured elastomers. The sensor enables reliable pressure response over a range of temperature (25−60 °C) and humidity (30−90% relative humidity) conditions, with resistance variations less than 5% and 3%, respectively. It is also able to detect vibrations with frequency up to 1500 Hz. Moreover, our sensor shows ultra-high durability, with high sensitivity and low hysteresis preserved after 1 million cycles. We demonstrate applications with the sensor in epidermal signal monitoring at different arteries, as well as accurate (>95%) surface texture recognition in combination with machine learning.

Mechanical sensors based on two-dimensional materials: Sensing mechanisms, structural designs and wearable applications

“…The third typical structural design to achieve enhanced pressure sensitivity with rapid dynamic response is through incorporation of the microstructures, such as micro-pyramids. Assembling a flexible membrane composed of graphene/PDMS micro-pyramid composite with interdigitated electrodes on the opposite PET substrate created a piezoresistive pressure sensor ( Yao et al., 2020 ). Although the viscoelasticity of PDMS led to frequency dependent piezo-sensing performance, the elasticity of graphene effectively improved the mechanical response frequency of the device, making the sensor exhibit a stable response signal to high frequency vibration of 1.5 kHz with slight distortion ( Yao et al., 2020 ).…”

“…In addition, some stirring properties (e.g., biocompatibility ( Huang et al., 2019a ), biodegradability ( Zhang and Tao, 2019 ), superhydrophobic ( Dinh et al., 2019 ), self-healing ( D'Elia et al., 2015 ; Lin et al., 2019 ), self-powering ( Wang et al., 2018 ), visualization ( Deng et al., 2017 ; Yang et al., 2017b ), gas permeability ( Sun et al., 2018 ), flame retardancy ( Wang et al., 2020a ), acid alkali-resistance ( Wang et al., 2020a )) have also been achieved, which further broaden the application scope of 2D materials based-wearable mechanical sensors. In the future, combining wearable sensors with machine learning and artificial intelligence technologies to build machine learning-assisted smart sensors will become the theme ( Yao et al., 2020 ; Zhou et al., 2020 ), which further promote the growth of many emerging diversified application markets and boost the prosperity of the Internet of Things to a new level. The structural designs and wearable applications of mechanical sensors based on 2D materials are illustrated in Figure 1 .…”

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Figure 1 Structural designs and wearable applications of mechanical sensors based on 2D materials Adapted from Refs. [( Cheng et al., 2015 ) ( Dinh et al., 2019 ) ( Wang et al., 2019b ) ( Zhang et al., 2020 ) ( Zhang and Tao, 2019 ) ( Yang et al., 2018 ) ( Yao et al., 2020 ), ( Tao et al., 2017 )].

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“… Adapted from Refs. [( Cheng et al., 2015 ) ( Dinh et al., 2019 ) ( Wang et al., 2019b ) ( Zhang et al., 2020 ) ( Zhang and Tao, 2019 ) ( Yang et al., 2018 ) ( Yao et al., 2020 ), ( Tao et al., 2017 )]. …”

Differential cardiopulmonary monitoring system for artifact-canceled physiological tracking of athletes, workers, and COVID-19 patients

“…By comparison to traditional devices that loosely couple to the wrist, skin-mounted technologies offer vastly superior measurement capabilities due to their persistent, intimate interfaces to the body (1)(2)(3)(4)(5). This mode of operation can support a range of clinically standard diagnostic assessments, such as those based on electrocardiography (2,(6)(7)(8)(9)(10)(11), photoplethysmography (10)(11)(12)(13)(14)(15), arterial tonometry (16)(17)(18)(19)(20), and others (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). A recent set of important capabilities follows from wide-bandwidth measurements of subtle motions and vibrations of the surface of the skin [i.e., mechano-acoustic (MA) responses] (35)(36)(37) that arise from activities of internal organs and accelerations due to global movements of the body (36,38,39).…”