Electrohydrodynamics (EHD) involves the dynamics of electrically charged fluids, which effectively means making fluids move using nothing but electric fields, making it an attractive idea for creating a pump out of. This is the topic of a 2023 paper by [Michael Smith] and colleagues in Science, titled “Fiber pumps for wearable fluidic systems”. The ‘fiber pumps’ as they call the EHD pumps in this study are manufactured by twisting two helical, 80 µm thick copper electrodes around a central mandrel, along with TPU (thermoplastic polyurethane) before applying heat. This creates a tube where the two continuous electrodes are in contact with any fluids inside the tube.

For the fluid a dielectric fluid is required to create the ions, which was 3M Novec 7100, a methoxy-fluorocarbon. Because of the used voltage of 8 kV, a high electrical breakdown of the fluid is required. After ionization the required current is relatively low, reported as 0.9 W/m, with one meter of this pump generating a pressure of up to 100 kilopascals and a flowrate of 55 mL/minute. One major limitation is still that after 6 days of continuous pumping, the copper electrodes are rendered inert due to deposits, requiring the entire system to be rinsed. Among the applications the researchers see artificial muscles and flexible tubing in clothing to cool, heat and provide sensory feedback in VR applications.

While the lack of moving parts as with traditional pumps is nice, the limitations are still pretty severe. What is however interesting about this manufacturing method is that it is available to just about any hobbyist who happens to have some copper wiring, TPU filament and something that could serve as a mandrel lying around.

Thanks to [Aaron Eiche] for the tip.

Now that we have decent VR goggles, the world is more desperate than ever for a decent haptic interface for interacting with computers. We might be seeing a new leap forward in this wild new haptic glove design from the Future Interfaces Group at Carnegie Mellon University.

The glove gives each fingertip and thumb a small haptic pad. The pads are driven by electro-osmotic pumps, which are effectively solid-state. They use electricity to move fluid to create small dimples on the pad to provide haptic feedback to the user. The pads have 20 pixels per square centimeter, are quick and responsive, and can deform up to 0.5 mm in less than half a second.

The lightweight and self-contained electro-osmotic pads mean the haptic system can be far lighter and more practical than designs that use solenoids or other traditional technologies. The device is also high resolution enough that a user can feel pressure from a surface or the edges of an object in VR. If you watch the video, some of the demonstrations are quite revolutionary.

We’ve seen some other great haptics projects before too, like these low-cost force feedback gloves. Video after the break.

[Thanks to Keith Olson for the tip!]