Hydrophobically Associated Functionalized CNT-Reinforced Double-Network Hydrogels as Advanced Flexible Strain Sensors

Abstract

Hydrogels have gained the attention of researchers worldwide and can be widely applied for use in medical technologies in human health and in industrial applications such as robotics. However, producing a hydrogel with proper mechanical properties, low hysteresis energy, quick shape recovery, and long-range strain sensitivity is still an ongoing development. More development into hydrogel technology could also lead to an increase in the effectiveness and lifespan of artificial joint replacements. Our hydrogels can be incorporated into the development of highly sensitive strain sensors for wearable electronic devices. To work toward developing these technologies, multifunctional dual crosslinked hydrogels were developed using lauryl methacrylate, acrylamide, and acid-functionalized multiwalled carbon nanotubes (A-MWCNTs). Due to the dual crosslinking, the synthesized hydrogels display outstanding mechanical performance (high fracture stress, strain, toughness, and tensile strength). In shape recovery, the materials recover their original shape after compression and maintain hydrostaticity. A low hysteresis energy of 11.57 kJ m −3 makes it a suitable candidate for strain sensing with high sensitivity (GF = 9.2 at 500% strain) to monitor different human motions (wrist, neck movements, flexion of the fingers, swallowing, and during speaking). Additionally, due to its good mechanical properties, the cyclic stability was monitored up to 300 cycles and the hydrogel still was mechanically stable and had the fastest response−recovery time of less than 130 ms during mechanical performance studies. Our hydrogels can be used to develop highly sensitive strain sensors for wearable electronic devices.

Polydopamine-Based Multifunctional Hydrogel for Flexible Supercapacitor and Pressure Sensor Applications

“…The low energy dissipation implies good resilience of the hydrogel. 37 The Young's modulus of the hydrogel was 0.38 MPa when the compressive strain was 60% (Figure 2d). It also showed that as the number of loading− unloading cycles increased, there was a slight increase in Young's modulus.…”

“…Figure c reveals that there is less energy dissipated (maximum value of 1.5 kJ m –3 ) during the 100 loading–unloading cycles test at 60% compressive strain. The low energy dissipation implies good resilience of the hydrogel . The Young’s modulus of the hydrogel was 0.38 MPa when the compressive strain was 60% (Figure d).…”

Polydopamine-Reinforced Hemicellulose-Based Multifunctional Flexible Hydrogels for Human Movement Sensing and Self-Powered Transdermal Drug Delivery

“…First, nanocomposite hydrogel can detect a wide range of activities from body movements as motion sensors (Figure ). To characterize the sensitivity of the sensor, the gauge factor (GF) was introduced and calculated according to the equation GF = ( R–R 0 )/ R 0 /ε, where ε is the strain. , When the tensile strain is within the limit stretching range of the P­(AM-AC)-HC-NP3 hydrogel, the relative resistance varies linearly, and the GF reaches about 1.04 (Figure S10a). The response and recovery times of the sensors are shown in Figure S10b.…”

Micelle–Micelle Cross-Linked Highly Stretchable Conductive Hydrogels for Potential Applications of Strain and Electronic Skin Sensors

“…10,11 These sensors can detect biological and mechanical activities and provide feedback through changes in their electrical output. 12 Over the years, a variety of dependable sensor materials have been developed, such as those utilizing carbon, 13−15 nanowires, 16 and conductive polymers. 17 However, a major obstacle faced by these sensors is their limited working range, large response time, and susceptibility to rapid conductivity deterioration under repeated large deformations.…”

“…Flexible strain and electronic sensors have captured a great deal of attention due to their broad potential applications in areas such as electric skin, − human movement detection, − health monitoring, , and energy storage. , These sensors can detect biological and mechanical activities and provide feedback through changes in their electrical output . Over the years, a variety of dependable sensor materials have been developed, such as those utilizing carbon, − nanowires, and conductive polymers .…”