A microvascular method for thermal activation and deactivation of shape memory polymers

The integration of material systems to include thermal activation and deactivation of shape memory polymers represents a key challenge for adaptive systems. Microvascular fluid flow with hot or cold fluid is used as an energy transport mechanism to activate and deactivate shape memory polymers, where the maximum temperature is limited by the hot fluid temperature to prevent overheating. A thin panel was constructed from the Veriflex® shape memory polymer and included an array of 10 parallel microvascular tubes. The panel is strained orthogonally to the tube direction in the activated state. An analytical steady-state surface temperature model is applied to predict the surface temperature range during activation. Thermography is used to measure the steady-state surface temperature for heating and the dynamic surface temperature for both heating and cooling. The decay constants and surface temperature range for heating and cooling are examined as a function of applied strain (0%–20%) and fluid flow rate (0–25 g min−1 of water). The decay constants depended strongly on flow rate and weakly on strain. The observed vascular cooling rate was up to six times faster than the comparable natural convection cooling rate for the flow rates tested. This faster cooling rate can significantly reduce temperature cycle times.