A pH-sensitive hydrogel-based smart switch for GI-tract payload release

In this paper, we demonstrate a low-cost and tunable pH-triggered smart switch which is based on the deflection of a conductive elastic membrane induced by the swelling of a pH-responsive hydrogel. The described switch comprises of a porous plate, a gel chamber, a deflectable conductive membrane, and an electrical isolation cell. The switching action is initiated through a sudden pH change (e.g., transition from acidic stomach to basic small intestine) which in turn results in diffusion/time controlled hydrogel swelling, making it suitable for ingestible capsules targeted for pH-controlled localized drug release in the gastrointestinal (GI) tract. A typical prototype (9 mm in diameter and 3.2 mm in thickness) responds to pH changes from 2 to 7 (transition from stomach to small intestine) with a response time of one hour.