In general, textile fabrics tend to close pores in wet conditions and open the pores in dry conditions, as fibers tend to swell and occupy more space when wet. However, for personal thermal regulation and comfort, it is desirable to have the opposite behavior, viz. opening the fabric pores in humid and sweating conditions for enhanced ventilation and cooling, and closing the pores in cold and dry conditions for heat retention.<br/><br/>Here we report on a novel approach of creating such unconventional fabric behavior by emulating the structure of guide cells in leaf stomata through a tailored moisture responsive polymer system in a fabric. We used moisture responsive polyacrylamide (PAAm) hydrogel at two different cross-linking levels at the edges of the cut slits (pores) in a stretchable knitted nylon fabric. Because the less cross-linked (LC) hydrogel at an outer layer swells more than that of the highly cross-linked (HC) counterpart at the inner layer at high wetness, the hydrogel layers (acting as artificial “guard cells”) bend outwards to open the slits (pores) in the fabric as surrounding wetness increases. The designed fabric with artificial leaf stomata increases the moisture permeability by 56% when the pores/slits open under wet conditions in comparison with that when the pores/slits are closed under dry conditions. Unlike the flap approach in many of the past studies, the fabric deforms within its own plane, thereby does not affect either the tactile comfort or the overall appearance. This moisture responsive fabric can have a direction application as smart functional clothing to maximum thermal comfort under changing physiological and environmental conditions. Besides, the concept can be extended to develop other responsive membranes, such as would dressings, controlled drug and nutrition and release, and other relevant industrial products.

Moisture responsive fabrics with artificial leaf stomata

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