We report novel thermoresponsive polyurethane membranes showing controlled release of liquid suspensions upon heating. Filling of inter-fiber spaces with different suspensions was performed by electrospraying the liquids during the electrospinning of nanofibers. Upon heating, individual nanofibers were shown to exhibit substantial contraction, resembling the shape memory effect, originating from the non-equilibrium microstructure of the nanofibers induced by the electrospinning process. At the mat level, this contraction resulted in a decrease in the overall mat volume, leading to the closure of the mat pores at the microscopic scale. This mechanism was used as a driving force for the expulsion of the encapsulated suspensions upon heating. The liquid flow within the mat pores was studied using confocal microscopy with a fluorescent suspension. Image analysis revealed more than 80 % of the fluid to be flowing from the heated surface to the free surface of the mat upon activating the contraction of the fibers. This important result opens the way to novel medical fabrics for sustained liquid drug delivery for applications such as topical treatment of severe skin diseases, wound healing or smart implants.
