Ready-to-wear strain sensing gloves for human motion sensing

Toward flexible piezoresistive strain sensors based on polymer nanocomposites: a review on fundamentals, performance, and applications

The fundamentals, performance, and applications of piezoresistive strain sensors based on polymer nanocomposites are summarized herein. The addition of conductive nanoparticles to a flexible polymer matrix has emerged as a possible alternative to conventional strain gauges, which have limitations in detecting small strain levels and adapting to different surfaces. The evaluation of the properties or performance parameters of strain sensors such as the elongation at break, sensitivity, linearity, hysteresis, transient response, stability, and durability are explained in this review. Moreover, these nanocomposites can be exposed to different environmental conditions throughout their lifetime, including different temperature, humidity or acidity/alkalinity levels, that can affect performance parameters. The development of flexible piezoresistive sensors based on nanocomposites has emerged in recent years for applications related to the biomedical field, smart robotics, and structural health monitoring. However, there are still challenges to overcome in designing high-performance flexible sensors for practical implementation. Overall, this paper provides a comprehensive overview of the current state of research on flexible piezoresistive strain sensors based on polymer nanocomposites, which can be a viable option to address some of the major technological challenges that the future holds.

Protocol for fabricating electroless nickel immersion gold strain sensors on nitrile butadiene rubber gloves for wearable electronics

This protocol describes the fabrication of patterned conductive gold films on nitrile butadiene rubber (NBR) gloves for wearable strain sensors using electroless nickel immersion gold (ENIG) plating, a solution-based metallization technique. The resulting NBR/ENIG films are strain sensitive; resistance measurements of a patterned sensing array can be used to map human hand motions. This protocol also describes challenges related to the ENIG process and troubleshooting steps to achieve conformal gold films for strain sensing over a large working range.

For complete details on the use and execution of this protocol, please refer to Mechael et al. (2021).

•

Detailed protocol to prepare strain sensors on nitrile butadiene rubber (NBR) gloves

•

Procedure to activate NBR for electroless nickel immersion gold (ENIG) metallization

•

Patterned ENIG deposition by airbrushing a commercially available latex emulsion

•

Tensile strain increases the resistance of the ENIG film for wearable motion sensing

Ultrathin and Highly Tough Hydrogel Films for Multifunctional Strain Sensors

With good flexibility and biocompatibility, hydrogel-based sensors have been widely used in human motion detection, artificial intelligence, human-machine interface, and other fields. Previous research on hydrogel-based sensors has focused on improving the mechanical properties and signal transmission sensitivity. With the development of human smart devices, there is an increasing demand for hydrogel sensor comfort and more application functions, such as ultrathin structures and recognition functions for contact surfaces, which are realized with higher requirements for the thickness, flexibility, friction resistance, and biocompatibility of hydrogels. Inspired by the ultrathin and flexible characteristics of human organ biofilms, we constructed conductive hydrogel films by using the flim-casting and glycerol-H₂O secondary hydration methods. This ultrathin structure enables the hydrogel films to have a high elongation at break of 523.3%, a stress of 3.5 MPa, and a good friction resistance. Combined with the excellent sensing properties (gauge factor = 2.1 and a response time of 200 ms), the hydrogel film-based sensor can not only record human motion signals but also recognize the surface texture and roughness of objects, such as glass, brushes, wood, and sandpaper with mesh sizes of 80, 50, and 24, accurately. In addition, this hydrogel film has a series of excellent properties such as UV shielding, antiswelling ability, and good biocompatibility. This research provides a novel way for the development of emerging soft-material smart devices, such as hydrogel-based electronic skin and soft robots.