关键词: 乙烯-醋酸乙烯酯共聚物(EVA), 功能填料, 双向形状记忆, 应变传感, 电致驱动

Abstract: Artificial muscles can produce reversible expansion, twisting, bending, stretching, and other motions under the action of external stimuli (heat, electricity, light, magnetism, humidity, pressure, etc.), which holds potential application value in robotics, medicine, aerospace and other fields. As a class of intelligent stimulus-responsive materials, two-way shape memory polymer (2W-SMP) is an excellent substrate for preparing artificial muscles, because it can facilitate the reversible transition between its original and temporary shapes by adjusting the ambient temperature. However, 2W-SMP has shortcomings such as poor thermal conductivity, slow response speed, and single response mode. Therefore, increasing the response speed of 2W-SMP, diversifying its stimulus-response modes, and achieving precise control over reversible actuation strain are of great significance for the application and development of 2W-SMP in the field of artificial muscles.
Ethylene-vinyl acetate copolymer (EVA) is a semi-crystalline polymer. Research indicates that cross-linked EVA fibers possess excellent two-way shape memory properties, large reversible actuation strains, good flexibility, and designability. In this paper, nano hexagonal boron nitride (h-BN) was used as thermal conductive fillers, and carbon nanotubes (CNTs) as conductive fillers. BN/EVA composite fibers were prepared by melt spinning process, and CNTs/BN/EVA composite fibers with skin core structure were prepared by swelling and impregnation method. The experimental results show that the CNTs were closely combined with the fiber matrix, forming a good electrically conductive path on the surface of the fiber, and the electrical conductivity of the CNTs/BN/EVA composite fibers could reach 58.03 S/m. The CNTs/BN/EVA composite fibers have good strain sensing performance, with a detection range of up to 281%, and high sensitivity and linearity (in the range of 175%-281% strain, Gauge Factor (GF) of 35.19, R2=99.03%), with response and recovery times of 196 ms and 189 ms, respectively. The twisted CNTs/BN/EVA composite yarns could be rapidly warmed up to 111.45 ℃ in 12 s at 18 V and exhibit stable temperature rise and fall behavior under periodic electrical stimulation conditions, achieving precise regulation of the electrically induced reversible actuation strain in yarn-based artificial muscles.
In summary, the EVA-based composite fibers prepared in this thesis combine excellent two-way shape memory properties, reversible electric-driven properties and strain sensing properties, integrate actuation and sensing capabilities into one, and have potential applications in the fields of artificial muscles, wearable devices and robotics.

Key words: ethylene-vinyl acetate copolymer (EVA), functional fillers, two-way shape memory, strain sensor, electro-actuation