Fig. 3. Electroadhesion of QDM gel to patch a cut in the Alg tube wall.

a Schematic of test setup. An aqueous solution of 0.1 wt% FeCl₃ is pumped through the lumen of the Alg tube, which is submerged in an aqueous bath of 0.1 wt% tannic acid. If the FeCl₃ leaks out of the tube, it reacts with the tannic acid and a black precipitate is formed immediately in the bath. b When the tube is intact, there is no leakage and the bath is clear. c Tube is punctured with a needle to create a hole of 400 µm diameter. d Tube is cut to a length of 7 mm with a blade. In (C) and (D), as the fluid in the tube leaks out, the black precipitate can be seen in the bath. e The tube from (d) is patched by a QDM gel, and when flow is resumed through the tube, no leakage can be seen. f A pressure gauge placed upstream of the tube records the pressure in the tube. The pressure drops to near-zero in the case of a cut in the tube (similar to (d)) as the fluid leaks out. When the tube is patched up (similar to (e)), the pressure is restored to its original value.