VR glove from the 3D printer

Dorina Opris, head of the Functional Polymeric Materials research group, and Empa researcher Patrick Danner are part of a large-scale project on electroactive polymers called "Manufhaptics". The aim of the four-year project led by Herbert Shea from EPFL's Soft Transducers Lab is a glove that makes virtual worlds tangible. The decisive factor here is that all of the glove's components, which exert various forces on the surface of the hand, should be producible using a 3D printer. In other words, this is about researching new materials where the production method is considered from the outset.

The research teams from EPFL, ETH Zurich and Empa want to integrate three different types of actuators into the glove so that virtual surfaces feel real and the objects can be grasped in the right size: On the underside of the fingers, nubs can grow upwards to imitate a certain texture of a surface. Electrostatic brakes are mounted in the area of the finger joints, which stiffen the glove and block the joints. This simulates larger, solid objects that offer resistance when touched. The third type of actuators that complete the virtual experience are called DEA, short for dielectric elastic actuators. These DEA are used on the back of the hand; they tighten the outer skin of the glove so that it fits perfectly in all areas. They can also exert pressure on the surface of the hand during the VR experience. DEA are Empa's sub-project.

Millimetre-sized, hydraulically reinforced electrostatic actuators provide a sense of touch and texture (left). High force electrostatic clutch actuators that can lock the finger joints to make virtual objects feel solid (centre). Multi-layer dielectric elastomer actuator for active glove sizing and localised compression (right). Illustration: Herbert Shea, EPFL (2021)

Dorina Opris, the head of the research group, has years of experience with such electroactive polymers. "These elastic polymers react to electric fields and contract like a muscle," explains the researcher. "But they can also serve as a sensor, absorbing an external force and generating an electrical impulse from it. We are also thinking of using them to generate energy locally: Movement can generate electricity anywhere."

The Manufhaptics project presents the researcher and her colleague Patrick Danner with new challenges. "Until now, we have produced our polymers with the help of solvents by means of chemical synthesis," explains Opris. Now everything has to work without solvents: The plan is to stack up to 1000 fine layers from the 3D printer, always alternating between the electroactive polymer and a current-conducting layer.

"Solvents must be avoided with this type of production method," says Opris. And Patrick Danner explains the next difficulty: the two different inks required for this must have exactly the right consistency to flow out of the 3D printer's nozzle. "Our project partner Jan Vermant from ETH Zurich wants something with similar properties to a hand cream. It should come out of the printer easily and then remain dimensionally stable on the base". And then this creamy layered structure still has to cross-link to form the right polymer.

After a long series of tests, Danner has found a promising formulation - a cream that is fluid enough and at the same time dimensionally stable, and from which electroactive polymers can be created in a single step. His colleague Tazio Pleji at ETH Zurich, a member of Jan Vermant's research team, has successfully processed the material into several layers in his 3D printer - always alternating between polymer and electrode material. There are not yet 1000 layers, but only around 10, and the artificial muscle from the 3D printer does not yet function satisfactorily.

However, Opris and Danner are confident that they will master the task together with the printing specialists at ETH Zurich - possibly as the first research team in the world. The only scientific competitors in this field are based at Harvard University in Massachusetts.

Source: Empa