Piezoresistive 3D graphene–PDMS spongy pressure sensors for IoT enabled wearables and smart products

Abstract

Recently, 3D porous graphene-polymer composite-based piezoresistive sensors have drawn great interest of researchers in the field of flexible electronics owing to their ultralightweight nature, compressability, robustness, and excellent electromechanical properties. In this work, we present a facile recipe for developing repeatable, reliable, and linear 3D graphene-PDMS spongy sensors for internet-of-things (IoT)-enabled wearable systems and smart consumer products. Fundamental morphological characterization and sensing performance assessment of the piezoresistive 3D graphene-polymer sensors were conducted to establish its suitability for the development of squeezable, flexible, and skin-mountable human motion sensors. The density and porosity of the sponges were determined to be 250 mgcm-3 and 74% respectively. Mechanical compressive loading tests conducted on the sensors showed an average elastic modulus as low as ~56.7 kPa. Dynamic compressive force-resistance change response tests conducted on four identical sensors revealed a linear piezoresistive response (in the compressive load range 0.42–3.90 N) with an average force sensitivity of 0.209±0.027 N-1. In addition, an accelerated lifetime test comprising 1500 compressive loading cycles (at 3.90 N uniaxial compressive loading) was conducted to demonstrate the long-term reliability of the sensor. To test the applicability of the sensors in smart wearables, four identical graphene-PDMS sponges were configured on the fingertip regions of a soft nitrile glove to develop a pressure sensing smart glove for real-time haptic pressure monitoring. The sensors were also integrated into Philips electronic shaver to realize smart shaving applications with the ability to monitor shaving motions. Furthermore, the readiness of our system for next-generation IoT-enabled applications was demonstrated by integrating the smart glove with an embedded system software utilizing the Arduino-Uno platform. The system was capable of identifying real-time qualitative pressure distribution across the fingertips while grasping daily life objects, thus establishing the suitability of such sensors for next-generation wearables for prosthetics, consumer devices, and personalized healthcare monitoring devices.

Nanomaterials‐Based Bioinspired Next Generation Wearable Sensors: A State‐of‐the‐Art Review

“…The phenomenon could be further explained by observing the unprocessed resistance change signal in response to 0.86 N uniaxial compressive loading of an improved graphene-PDMS piezoresistive sensors reported by Sengupta et al (shown by the plot in Figure 12m). [36] As observed from the plot in Figure 12m, the sensor demonstrated an initial sharp increase in resistance followed by a steady decrease in resistance in response to uniaxial compressive loading, which is manifested as overshooting behavior of the resistance change response. Similar behaviors have been observed previously by several researchers.…”

“…[18][19][20][21] In particular, wearable mechanical sensors reported lately can track a multitude of vital human physiological parameters including pulse rate, [19] gait, [22,23] respiration rate, [24] and various joint movements. [18,25,26] In general, based on their underlying sensing mechanism, mechanical sensors can be categorized into piezoelectric, [27][28][29][30][31] capacitive, [32][33][34][35] piezoresistive, [25,26,[36][37][38][39][40] and others (such as triboelectric, [41,42] optical, [43,44] and transistor, [45][46][47] based). Of all the major sensing mechanisms, capacitive and piezoresistive sensing mechanisms remain the most popular and widely used because of their simple implementation, excellent resolution, and superior static and dynamic sensing performance.…”

An Inkjet-Printed Piezoresistive Bidirectional Flow Sensor

“…In addition to the strain induced resistance change phenomenon demonstrated by regular metallic strain gauges (owing to geometric deformation), the strain gauge reported here also employs conductive domain discontinuity mechanism commonly observed in polymer-nanomaterial composite based strain sensors [3], [12]- [14]. When the cantilever tip is displaced downwards, a tensile stress acts on the strain gauge on the top (printed near the cantilever support end) which causes geometric deformation/strain leading to a change in resistance.…”

Fabric-like Electrospun PVAc–Graphene Nanofiber Webs as Wearable and Degradable Piezocapacitive Sensors

“…Historically, strain and pressure sensing devices have relied on different sensing mechanisms, namely piezo-resistive, − piezoelectric, − and capacitive. − Other mechanisms utilizing transistors for pressure sensing have also been reported in the literature. − More recently, the triboelectric sensing mechanism has also been employed in the development of pressure and strain sensors. , Though the piezoelectric sensing mechanism offers the advantage of self-powered sensing, their inability to sense static pressure places a major hindrance on their applications in tasks requiring both static and dynamic pressure sensing. In contrast, piezoresistive sensing offers functionality in a wide range of pressure sensing conditions, including static, quasi-static, and dynamic pressure/strain sensing.…”