Strong and Stretchable Gels for Electroadhesion

Abstract

Electroadhesion (EA) was first shown between cationic and anionic gels: when the two are contacted under an electric field (10 V DC, for ~ 20 s), they adhere strongly and remain adhered after the field is removed. Recently, our lab demonstrated that EA can also be induced between a cationic gel and animal tissues. This suggests the intriguing possibility of using EA in surgery: i.e., for gels to be electroadhered over tears in tissues. However, current gels fail to properly seal tissue-tears because either they are not strong enough (they break when stretched over the torn tissue) or do not adhere well enough to the tissue. This project aims to create a cationic gel that is strong (i.e., has high elongation-at-break ε and tensile strength TS) and exhibits strong adhesion to tissue by EA (i.e., has high pull-off strength). Our base gel, made by polymerizing an acrylamide monomer (termed ‘QDM’), is fortified by a second polymer. The optimal second polymer is shown to be gelatin, which forms physical gels upon cooling from a hot solution. QDM/gelatin gels are interpenetrating networks (IPNs) and exhibit ~ 20-30X higher ε and TS compared to QDM alone. We proceed to test if our strong gels can seal tears in chicken intestines. A tear in the tube is patched by the QDM/gelatin gel using EA, and water is then sent through the patched tube. Even for large tears (~ 3-4 mm width), the patched tube allows water to flow at a pressure exceeding 80 mm Hg (normal fluid pressure in the body). This suggests that EA could indeed be implemented in surgery using our strong QDM/gelatin gels.