A Flexible Strain Sensor with High Electrical Conductivity, Rapid Electrothermal Response, and High Strain Sensitivity for Real‐Time Monitoring of Human Joint Movement

Abstract

Here, a flexible film, called PPA film, is designed as a multifunctional sensor with high electrical conductivity, rapid electrothermal response, and high strain sensitivity. The film contains polyvinyl alcohol (PVA), graphene nanosheets (GNs), nanocellulose crystals (CNCs), polydopamine (PDA), and silver nanoparticles (Ag NPs), symbolized as PPA film. The CNCs enhance the dispersion of the GNs during film formation; the stacked GNs change heat conduction and resistance during film bending; PDA serves as a linking agent; Ag NPs improve the conductivity (i.e., 2.65 × 103 S/m) of the film during electrothermal response measurement. A flexible strain sensor designed from PPA films is mounted on the skin surface of human joints to monitor human movement in real time. The sensor exhibited good stability and cycling durability, i.e., the resistance variation remained stable during the bend‐release repetitions for 600 cycles at 1.2 % strain. The flexible sensors exhibited highly sensitive to bending strain, i.e., 30.5 of the gauge factor (GF), and can be applied to monitor bending motions of human joints, such as finger, wrist, elbow, and knee joints.In addition, the PPA films exhibit very high joule heat generation ability and demonstrate its applicability as a joint or stomach warmer and sensor. The as‐designed flexible sensor is a promising candidate for application in environmentally friendly and multifunctional wearable devices.

Graphene and Silver Nanoparticle-Coated Poly(vinyl) Alcohol/Graphene Oxide/Dioctyl Terephthalate: Bis(2-hydroxyethyl) Terephthalate Composite Strain Sensors

“…The results of this study were compared with those of flexible polymer substrates such as PVA, PI, and PET, widely used in strain sensor production. Figure 9 represents the performance indicator comparison of reported the gauge factor and strain level of graphene-based polymer by He et al, 66 Li et al, 67 Liu et al, 68 Lynch et al, 69 and Htwe et al 70 As shown in Figure 9, graphene/AgNPs spray-coated PVA/GO/BHET strain sensors possess remarkable sensitivity at a very low strain level of 0.04%.…”

Paper-based sustainable biosensors

“…91,92 Paper is a favorable substrate to manufacture POC in-vitro diagnostic devices due to its abundant availability, affordability, chemical stability, biodegradability, prominent porous fibrous network with high surface area for interactions, and natural capillary-driven mass transport of liquid samples. 93–97 Various well-established technologies for the manufacture and processing of paper have been applied for the fabrication of paper-based microfluidic devices, including folding, cutting, 98,99 masking, 100,101 laser writing, 102 and printing. 103–105 However, paper can vary immensely based on its composition, internal structure, and wettability owing to its sources and manufacturing method, 106 for example, filter paper, 107,108 chromatography paper, 109 common printer paper, 110 and paper towels.…”