膜-基结构光热敏感凝胶膜起皱临界波长与临界应力分析

Study of the Critical Wavelength and Critical Stress of Wrinkling of Thin Photo-thermal Sensitive Hydrogel Film on Elastic Substrate

粘附于弹性基底的光热敏感凝胶薄膜-基底结构广泛应用于微机械、生物传感器和促动器等领域。当光强或温度变化时,光热响应凝胶膜发生溶胀,由于基底的限制作用,凝胶膜中存在的压应力可能使凝胶膜发生起皱失稳。基于光热敏感凝胶溶胀大变形理论与冯卡门几何非线性薄板理论,本文对膜-基结构光热敏感凝胶膜起皱失稳机理进行分析,计算了不同光强、温度、溶剂化学势及刚度系数条件下凝胶膜起皱的临界波长和临界应力。结果表明:当环境的光强和温度相同时,溶剂的化学势越大,光热敏感凝胶膜起皱的临界应力越大;当溶剂的化学势相同时,环境的光强越强,温度越高,临界应力越大;在环境温度和光强相同的情况下,光热敏感凝胶膜-基底结构的刚度系数越小,起皱时的临界波长越大;在刚度系数相同的情况下,环境温度越低,光强越弱,起皱临界波长越小。

Thin photo-thermal sensitive hydrogel film on elastic substrate has been widely used in the fields of micromechanics system (MEMS), biosensors and actuators. Due to the confinement of the elastic substrate, when the photo-thermally sensitive hydrogel swelling with the change of external temperature or light intensity, the existence of the compressive stress in the hydrogel film makes the film wrinkle. Based on the finite deformation theory of the photo-thermally sensitive hydrogel and von Karman nonlinear plate theory, this paper studied the wrinkling mechanism of the photo-thermally sensitive hydrogel film and analyzed the effects of light intensity, temperature, chemical potential of the solvent and the stiffness coefficient of the substrate on the critical wavelength and critical stress of wrinkling of photo-thermally sensitive hydrogel film. The results show that:when the temperature and light intensity keep the same, the critical stress decreases with increasing chemical potential of the solution;when the chemical potential keeps the same, the higher the light intensity and temperature, the greater the critical stress;when the light intensity and the temperature keep the same, the smaller the stiffness coefficient, the greater the critical wavelength;for the same stiffness coefficient, the lower light intensity and the temperature, the smaller the critical wavelength.