Effect of polymer nanofibers thermoelasticity on deformable fluid-saturated porous membrane

We describe a novel thermo-responsive fiber mat showing controlled release of liquids upon heating. The fiber mat was composed of electrospun thermoplastic polyurethane (TPU) nanofibers, with liquid-filled inter-fiber spaces (pores). On heating above 60 °C, nanofibers underwent substantial contraction. This solid deformation was attributed to the heat-induced relaxation of a non-equilibrium stretched state of the polymer fibers formed during the electrospinning process [Alhazov et al., 2013]. Fiber mat contraction drove expulsion of a glycerol/water solution stored in the pores of the mat, as evidenced by microscopic observations. The liquid flow in the deformable porous medium was analyzed, by means of confocal microscopy, which demonstrated liquid drainage from the mat as a function of temperature. UV-spectrophotometry revealed that 80% of a dyed liquid was expelled from the mat upon heating to 90 °C from room temperature. Finally, the potential of the thermoelastic fiber mats as reliable time-temperature indicator (TTI) was demonstrated with a simple model device in which the fiber mat was designed to release a liquid dye as an indication of the time-temperature history.