Strategies for Designing Stretchable Strain Sensors and Conductors

Abstract

Flexible and stretchable electronics are attracting tremendous attention for their enormous future potential in wearable technologies. Flexible and stretchable sensors and conductors are the key components of wearable devices for potential applications such as human motion detection, human health monitoring, and human–machine interfaces. One critical requirement for them is to show high level of wearability (bendability and stretchability) and meanwhile to retain their functionality and reliability under large mechanical deformation. To this end, a wide range of materials and structural designs are developed to construct these sensors and conductors. Here, the recent advances in the development of new piezoresistive materials and microstructural motifs that endow electronics with flexibility and stretchability are summarized. Challenges and future opportunities are discussed in terms of the multimodal and multidirectional sensing capabilities, the trade‐off between sensitivity/conductivity and stretchability, multifunctionality, linearity (multiple linear region phenomenon), and integration with flexible power and communication devices.

Polymer‐assisted fully recyclable flexible sensors

“…Besides, when the device is applied with mechanical stretching, the resistance change is spontaneously determined by the reorganization of carbon nanotubes and the deformation of polyurethane. [34][35][36] For the blending type of electronic sensors, the recycling ability is mainly ascribed to the polymeric matrix, because the blended microparticles or nanoparticles without the polymer assistance commonly present limited performance of shaping or freestanding. In terms of the recycling or reprocessing ability, thermoplastic polymers usually exhibit excellent thermal or solution processing ability due to the considerable fluidity of linear chains at high temperatures, or remarkable solubility in a good solvent.…”

“…Taking the blending system composed of polyurethane elastomer and carbon nanotubes as an example, its resistance can be responded to the external stimuli of both temperature change and light irradiation, which is originally resulted from the conductivity change of carbon nanotube. Besides, when the device is applied with mechanical stretching, the resistance change is spontaneously determined by the reorganization of carbon nanotubes and the deformation of polyurethane 34‐36 …”

Highly sensitive, stretchable and durable strain sensors based on conductive double‐network polymer hydrogels

“…Apart from two major contributing factors mentioned above, a minor contribution to the sensitivity could come from the geometric effect (shape change under deformation) of the ion-containing hydrogel according to the result from Figure 4b. [25,76] The potassium ions in thermal initiator (KPS) can potentially offer ions conduction, allowing for electrical conductivity of hydrogels. [63,77]…”

3D Printed Flexible Strain Sensors: From Printing to Devices and Signals

“…A small amount of reports have reviewed the research progress of 3D printed flexible sensors with a brief overview on several specifically functional sensing devices merely. [ 24,25 ] The evolution of 3D printed polymer‐based flexible strain sensors on materials preparation and device design has not been discussed in depth. To this end, as demonstrated in Figure , the presented work provides state‐of‐the‐art advances in 3D printed strain sensors, which is organized in three following sections.…”