Abstract
Self-folding origami utilizes shape memory polymers (SMPs) to enable deployable space structures, such as those intended for large-scale, low-frequency radio interferometry. The size of structure that may be deployed is limited by the capacity of the smart material to do work. Previous studies focused on activation mechanisms and the kinematics of self-folding polymers, but have largely neglected an evaluation of the energy stored in the folding hinge. This paper seeks to characterize the work done by self-folding origami hinges made of pre-strained polystyrene (PSPS) as it deforms due to the shape-memory effect. SMP samples are patterned with black ink hinges and exposed to an infrared (IR) light. The ink absorbs thermal energy from the light, which leads to local heating and shrinking in the hinge region. Activation of the self-folding response, e.g. shrinking, occurs when the material reaches a temperature higher than its glass transition temperature, and a gradient in shrinking causes the sample to fold. The self-folding process is sensitive to physical constraints and changes in energy input into the sample. Thus, we will evaluate the energy stored in the self-folding hinge by measuring the work done under varying thermal stimuli in an array of tests that include universal material shrinkage and single-hinge folds. We evaluate hinge torque based on a dynamic analysis of the motion of the self-folding sheet. Quantification of the capacity of self-folding origami hinges to do work enables the design of deployable space structures by not only considering the activation mechanism and self-folding kinematics, but also accounts for the size of structure that may be deployed.
