Is there a method to stick hard and soft materials together with none tape, glue or epoxy? A brand new study published in ACS Central Science shows that applying a small voltage to certain objects forms chemical bonds that securely link the objects together. Reversing the direction of electron flow easily separates the 2 materials. This electroadhesion effect could help create biohybrid robots, improve biomedical implants and enable recent battery technologies.
When an adhesive is used to connect two things, it binds the surfaces either through mechanical or electrostatic forces. But sometimes those attractions or bonds are difficult, if not unattainable, to undo. In its place, reversible adhesion methods are being explored, including electroadhesion (EA). Though the term is used to explain a number of different phenomena, one definition involves running an electrical current through two materials causing them to stay together, because of attractions or chemical bonds. Previously, Srinivasa Raghavan and colleagues demonstrated that EA can hold soft, oppositely charged materials together, and even be used to construct easy structures. This time, they desired to see if EA could reversibly bind a tough material, similar to graphite, to a soft material, similar to animal tissue.
The team first tested EA using two graphite electrodes and an acrylamide gel. A small voltage (5 volts) was applied for a number of minutes, causing the gel to permanently adhere to the positively charged electrode. The resulting chemical bond was so strong that, when one among the researchers tried to wrench the 2 pieces apart, the gel tore before it disconnected from the electrode. Notably, when the present’s direction was reversed, the graphite and gel easily separated — and the gel as a substitute adhered to the opposite electrode, which was now positively charged. Similar tests were run on a wide range of materials — metals, various gel compositions, animal tissues, fruits and veggies — to find out the phenomenon’s ubiquity.
For EA to occur, the authors found that the hard material must conduct electrons, and the soft material must contain salt ions They hypothesize that the adhesion arises from chemical bonds that form between the surfaces after an exchange of electrons. This will explain why some metals that hold onto their electrons strongly, including titanium, and a few fruits that contain more sugar than salts, including grapes, didn’t adhere in some situations. A final experiment showed that EA can occur completely underwater, revealing an excellent wider range of possible applications. The team says that this work could help create recent batteries, enable biohybrid robotics, enhance biomedical implants and way more.
