The material is created by a 3D printing process where rigid particles are embedded within a more flexible polymer. When squeezed, the material's surface changes from smooth to a pattern determined by the spacing and shapes of the implanted harder particles; when released, it reverts back to the original form.
The findings, which the researchers say could lead to a new class of materials with dynamically controllable and reversible surface properties, are reported in a paper in the journal 'Advanced Functional Materials' co-authored by MIT graduate student Mark Guttag and Mary Boyce, a former MIT professor of mechanical engineering who is now dean of engineering at Columbia University.
The report says that the system can produce simple, repetitive patterns of bumps or creases, which could be useful for changing the aerodynamic resistance of an object, or its reflectivity. But by arranging the distribution of the hard particles, it can also be used to produce highly complex surface textures — for example, creating microfluidic channels to control the movement of liquids inside a chemical or biological detector.
Surface textures can be important in a variety of applications, including camouflage, making surfaces that repel or attract water, controlling the motion and turbulence of fluids, and limiting the build-up of organisms on surfaces such as ship hulls.
Guttag and Boyce believe that the polymer can be triggered by influences other than pressure, such as electric impulses, temperature or humidity. They also say that changing the shape of the rigid particles to be elongated could create surfaces that have high friction in one direction and low in another.
