Engineers at the Massachusetts Institute of Technology (MIT) have created a synthetic, sticky hydrogel that is more than 90 percent water. The transparent, rubber-like hydrogel adheres to surfaces such as glass, silicon, ceramics, aluminum, and titanium with a toughness comparable to the bond between tendon and cartilage on bone.

The biocompatible adhesive may be suitable for a range of health-related applications, such as biomedical coatings for catheters and implantable sensors.

To create the stretchy hydrogel, the researchers mixed a solution of water with a dissipative ingredient. The hydrogel was then placed atop various surfaces, including aluminum, ceramic, glass, and titanium, each modified with functional silanes — molecules that created chemical links between each surface and its hydrogel.

The engineers tested the hydrogel’s bond using a standard peeling test, in which they measured the force required to peel the hydrogel from a surface. On average, the team found that the hydrogel’s bond was as tough as 1,000 joules per square meter.

In addition to determining the hydrogel’s toughness with a hammer and a weight, Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in MIT’s Department of Mechanical Engineering, and his colleagues explored the adhesive's use in robotic joints, using small spheres of hydrogel to connect short pipes to simulate robotic limbs.

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