Soft actuators hold promising application prospects in emerging fields such as wearable sensing, intelligent medical assistance, and soft robotics. Among them, soft actuators based on electrothermal responsive liquid crystal elastomers (LCEs), especially LCE fiber actuators, have garnered significant attention due to their rapid response, ease of integration, and convenient molding. However, the deformation modes of existing electrothermal responsive LCEs, prepared through doping, embedding, or coating conductive materials, are fixed upon completion, making it challenging to meet the urgent need for diverse deformation capabilities in soft actuators.

To address this challenge, Professor Zhongqiang Yang's research team from the Department of Chemistry, Tsinghua University, has innovatively developed a microfluidic-assisted electrothermal responsive LCE fiber capable of in-situ deformation editing. This fiber employs a hollow LCE structure as the shell and creatively introduces gallium and mercury, two liquid metals, as the conductive core. Through microfluidic technology, the distribution of these two metals within the core is precisely controlled, endowing the LCE fiber with unprecedented deformation flexibility. Mercury's resistivity is 3.5 times that of gallium, leading to significantly higher Joule heat generation in mercury segments during electrification. This results in pronounced local contraction differences, enabling precise control and editing of the LCE fiber's deformation.

Figure 1. Schematic illustration of the in-situ programmable microfluidic-assisted electrothermal responsive LCE fiber

Figure 2 The relationship between the injection volume of gallium and mercury and their positions within the LCE fiber

Figure 3 The relationship between the magnitude of the electric current and the shrinkage rate of the gallium and mercury segments of the LCE

Figure 4 Actuation deformation of a model hand

Experiments have demonstrated that when gallium and mercury are injected into the LCE fiber at a pre-set ratio and a constant current intensity is maintained, the fiber, as a flexible actuator, can actuate a model hand to perform complex and varied hand gestures, including delicate operations such as sequentially bending four fingers. Additionally, its broad adaptability is showcased in its application on a model dragon, where by adjusting the injection volume of gallium and mercury, the model dragon is capable of executing various dynamic movements, presenting a lifelike dragon dance performance.

Figure 5 Actuation deformation of a model dragon

This groundbreaking research achievement was published in the ACS Applied Polymer Materials under the title of "In situ Programmable Electrothermal Actuation of Liquid Crystal Elastomer Fibers Assisted by Microfluidics". The article was co-authored by Ph.D. candidate Zhang Xinyuhang and Liao Wei from the Department of Chemistry, Tsinghua University, serving as the first authors. Associate Professor Zhu Chongyu from the College of Chemistry and Chemical Engineering, Donghua University, also contributed to this work. Associate Professor Yang Zhongqiang from the Department of Chemistry, Tsinghua University, served as the corresponding author. This project received substantial support from the Tsinghua University Dushi Fund and the Open Fund of the Key Laboratory of Organic Optoelectronics and Molecular Engineering, Ministry of Education.