Fig. 1: Overview of the application of the packaging system.
From: Freestanding region-responsive bilayer for functional packaging of ingestible devices
a pH-sensitive polymer coating (green) remains intact and impermeable in the stomach (pH 1.5–3). In the small intestine, the pH rises (pH 6–7.4), causing polymer swelling and removal. The water-soluble PEG layer is then dissolved by the aqueous intestinal environment, thus revealing the capsule actuator cavity. b Chemical structure of Eudragit L 100 55 at pH values relevant to the stomach and small intestine. In the stomach, the structure is protonated, and the polymer is compact, while in the small intestine, the structure is deprotonated, causing monomers to repel each other and expand. c Overview of the bilayer coating process: (1) A polyimide sheet is placed on a hotplate, and PEG crystals are melted into a liquid film. (2) A 3D-printed polyethylene terephthalate glycol capsule is pressed onto a PEG film. (3) The polyimide and PEG layers are folded over the capsule and cooled until the PEG film solidifies. (4) The polyimide film layer is readily peeled off. (5) The sample is dip-coated in a pH-responsive polymer
