Soft robots are those that can move like living organisms and adapt to the surrounding environment. Compared with traditional rigid robots, the advantages of soft robots, in terms of material flexibility, human–computer interaction, and biological adaptability, have received extensive attention. Flexible actuators based on light response are one of the most promising ways to promote the field of cordless soft robots, and they have attracted the attention of scientists in bionic design, actuation implementation, and application. First, the three working principles and the commonly used light-responsive materials for light-responsive actuators are introduced. Then, the characteristics of light-responsive soft actuators are sequentially presented, emphasizing the structure strategy, actuation performance, and emerging applications. Finally, this review is concluded with a perspective on the existing challenges and future opportunities in this nascent research frontier.

Interface issues urgently need to be addressed in high-performance fiber reinforced composites. In this study, different periods of O₂ plasma treatment are proposed to modify twist-free polyimide (PI) filaments to improve hydrophilicity and mechanical and interfacial properties. Feeding O₂ produces chemically active particles to modify the filament surface via chemical reactions and physical etching. According to the X-ray photoelectron spectroscopy (XPS) results, the PI filaments exhibit an 87.16% increase in O/C atomic ratio and a 135.71% increase in the C–O functional group after 180 s O₂ plasma treatment. The atomic force microscope (AFM) results show that the root mean square roughness (Rq) of the treated PI filaments increases by 105.34%, from 38.41 to 78.87 nm. Owing to the increased surface oxygenic functional groups and roughness after O₂ plasma treatment, the contact angle between treated PI filaments and water reduces drastically from the pristine state of 105.08° to 56.15°. The O₂ plasma treated PI filaments also demonstrate better mechanical properties than the pristine PI filaments. Moreover, after O₂ plasma treatment, the adhesion between PI filaments and poly(amic acid) (PAA) is enhanced, and the tensile strength of the polyimide/poly(amic acid) (PI/PAA) self-reinforced composites increases from 136 to 234 MPa, even causing the failure mode of the composite changes from adhesive failure to partly cohesive failure.

Flexible wearable strain sensors with excellent sensing performance have received widespread interest due to their superior application capability in the field of human-computer interaction, sports rehabilitation, and disease diagnosis. But at present, it is still a considerable challenge to exploit a flexible strain sensor with high sensitivity and wide sensing range that is easily manufactured, low-cost, and easily integrable into clothing. MXene is a promising material sensitive enough for flexible sensors due to its superior conductivity and hydrophilicity. The warp knitting weft insertion textile structure gives the fabric excellent elasticity, making it suitable as a flexible, stretchable substrate. Therefore, utilizing a polyester elastic fabric with a warp knitting weft insertion structure, a fabric strain sensor with high sensitivity and wide sensing range prepared by layer-by-layer self-assembly of polyvinyl alcohol layers and MXene layers is reported in this study. The strain sensor exhibits high sensitivity (up to 288.43), a wide sensing range (up to 50%), fast response time (50 ms), ultra-low detection limit (a strain of 0.067%), excellent cycle stability (1000 cycles), and good washability. Besides, affixing the MXene/polyvinyl alcohol/polyester elastic fabric strain sensor on the joints can detect the movement of limbs. Therefore, the MXene/polyvinyl alcohol/polyester elastic fabric strain sensor demonstrates potential application opportunities in smart wearable electronic devices, and the researcher can also apply this method in the production of other flexible, intelligent wearable devices.

Polyimide (PI) films with excellent heat resistance and outstanding mechanical properties have been widely researched in microelectronics and aerospace fields. However, most PI films can only be used under ordinary conditions due to their instability of dimension. The fabrication of multifunctional PI films for harsh conditions is still a challenge. Herein, flexible, low coefficient of thermal expansion (CTE) and improved mechanical properties films modified by carboxylated carbon nanotube (C-CNT) were fabricated. Acid treatment was adapted to adjust the surface characteristics by using a mixture of concentrated H₂SO₄/HNO₃ solution to introduce carboxyl groups on the surface and improve the interfacial performance between the CNT and matrix. Moreover, different C-CNT concentrations of 0, 1, 3, 5, 7, and 9 wt.% were synthesized to use for the PI film fabrication. The results demonstrated that the 9 wt.% and 5 wt.% C-CNT/PI films possessed the lowest CTE value and the highest mechanical properties. In addition, the thermal stability of the C-CNT/PI films was improved, making them promising applications in precise and harsh environments.