The actuation forces of a hydrophilic liquid crystal elastomer (LCE) in response to water vapor was tested and modeled. These materials exhibit asymmetric swelling as water vapor is absorbed into one side of the elastomer film. This gives rise to deflection away from the water source. Deformation due to water vapor has shown to be on the order of seconds and is reversible which provides unique sensing and actuation characteristics for elastomer films. The constitutive behavior is modeled by using nonlinear continuum mechanics to predict internal changes in density of the liquid crystal elastomer and subsequent deformation by correlating moisture exposure with changes in the elastomer’s density. In order to compare the model and obtain a set material parameters, a micro-Newton measuring device was designed and tested to quantify the forces generated in the liquid crystal elastomer under bending. Forces ranging between 1 to 8 μN were measured as a function of the location of the water vapor source. The results provide important insight into chemical force response and sensing for a number of biomedical and microfluidic applications.

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