Recent Advances in Transparent Electronics with Stretchable Forms

Abstract

Advances in materials science and the desire for next‐generation electronics have driven the development of stretchable and transparent electronics in the past decade. Novel applications, such as smart contact lenses and wearable sensors, have been introduced with stretchable and transparent form factors, requiring a deeper and wider exploration of materials and fabrication processes. In this regard, many research efforts have been dedicated to the development of mechanically stretchable, optically transparent materials and devices. Recent advances in stretchable and transparent electronics are discussed herein, with special emphasis on the development of stretchable and transparent materials, including substrates and electrodes. Several representative examples of applications enabled by stretchable and transparent electronics are presented, including sensors, smart contact lenses, heaters, and neural interfaces. The current challenges and opportunities for each type of stretchable and transparent electronics are also discussed.

Liquid Metal–Based Soft Microfluidics

“…As long as the calculated pinning force is greater than the cohesion of the liquid metal itself (for example, EGaIn cohesion (SFT) is between 500 and 700 mN m −1 ), the liquid metal maintains the applied pattern. The maintenance of the pattern is aided by the increased adhesion of the liquid metal surface due to oxide skin formation and reduced SFT of the oxide skin . Furthermore, the fluidity of the LM permits the filling of microfluidic channels while the swiftly formed oxide skin adheres to the surface of the channel, and combined with the low SFT of the oxide skin this properties prevent outflow of the LM.…”

“…The maintenance of the pattern is aided by the increased adhesion of the liquid metal surface due to oxide skin formation and reduced SFT of the oxide skin. [1][2][3][4] Furthermore, the fluidity of the LM permits the filling of microfluidic channels while the swiftly formed oxide skin adheres to the surface of the channel, and combined with the low SFT of the oxide skin this properties prevent outflow of the LM. In contrast, mercury flows out of microchannels due to the absence of such an oxide skin.…”

“…Theoretically, the LM in a microfluidic system can be infinitely deformed while maintaining its conductivity. To date, LM‐based microfluidics have demonstrated excellent performance in soft, flexible and wearable electronics, soft robotics, biomedical sensors, and transient circuits . Moreover, the generation and operation of microdroplets is also an important part of the field of microfluidics research.…”

“…Room-temperature liquid metals (RTLMs), metals and alloys whose melting point is at or near room temperature, have attracted increasingly attention in the past years due to being endowed with both metallic and liquid natures, thus enabling broad application range, i.e., in flexible electronics, as wearable device, as sensors, and in soft robotics. [1][2][3][4] LM, on the one hand, possesses excellent electrical and thermal conductivities. On the other hand, distinguishing it from traditional metals, LMs exhibit good flowability, reconfigurability, and recoverability that can hardly be achieved by a solid metal.…”

“…To date, LM-based microfluidics have demonstrated excellent performance in soft, flexible and wearable electronics, soft robotics, biomedical sensors, and transient circuits. [1][2][3][4] Moreover, the generation and operation of microdroplets is also an important part of the field of microfluidics research. The fabrication of liquid metal droplets and the dispersion of microdroplets in elastomers have matured in recent years.…”