MorphingSkin Wants to Pump... You Up!

Imagine if you could feel the texture of each key on your phone’s virtual keyboard, and that each tap was met with force feedback that simulates the experience of using a mechanical keyboard. That would be a huge upgrade from the hollow and unpleasant experience of tapping on a hard, flat display that has no give to it. Now imagine that this type of experience was available not only on your phone, but on any imaginable surface, from walls to floors and furniture.

That is the idea behind a nascent technology called interactive surfaces. These are ordinary surfaces that have been instrumented to shapeshift in ways that allow them to provide haptic feedback or become tangible displays, for instance. But you will rarely encounter an interactive surface of this sort outside of a research lab because the technologies used to create them, like fluid-driven actuators, are bulky, noisy, and require a whole host of supporting components for operation.

The technology may soon become more prevalent, however. A group led by researchers at the University of California, Berkeley is hard at work in an effort to make interactive surfaces more practical for mainstream use. Toward that goal, they have developed what they call MorphingSkin. It is a multimodal, skin-like platform that uses compact and silent hydraulic pumps to build multifunctional interactive surfaces.

Most fluid-driven systems used in interactive surfaces rely on external pumps, valves, and motors. These parts are effective but are heavy, take up space, and make noise. MorphingSkin avoids those pitfalls by using a type of miniature hydraulic actuator called an electroosmotic pump (EOP). Unlike traditional pumps that have moving parts, an EOP generates flow directly by applying voltage across a special membrane in contact with fluid.

Each EOP is made from a pair of mesh-patterned electrodes with a thin pumping membrane sandwiched between them. When voltage is applied, the fluid moves across the membrane through electrokinetic effects. By reversing the voltage, the fluid can be pumped back the other way. This reversible, bidirectional flow is what gives MorphingSkin the ability to dynamically inflate or deflate small cavities within its structure, changing the shape or stiffness of the surface on demand.

The MorphingSkin platform is organized in layers. At the core is the flexible EOP circuit, which contains multiple tiny pumps that can be controlled independently. The circuit is fabricated on a flexible printed circuit board with stretchable interconnects so that the whole device can bend and flex without breaking.

Attached to the EOP layer are elastic shells that contain the liquid. Some of these shells serve as output layers, which change their shape or exert force when filled with fluid. Others act as reservoir layers, soft pouches that store extra fluid and supply it to the pumps as needed. Finally, connection layers with engraved millifluidic channels provide pathways for moving liquid around the device, linking the pumps, reservoirs, and outputs together into a continuous fluidic network.

The fluid itself is sealed inside and moved only by the EOPs, which means the system is quiet and self-contained. Depending on the geometry of the shells and the material properties chosen, the surface can push back with force, deform its shape, alter its transparency, or even change its apparent weight.

MorphingSkin is a practical option for building interactive surfaces for real-world applications. If the system can be proven outside of the lab, we could find ourselves surrounded by walls, tables, or even clothing that can transform its shape, feel, and function in the future.