Delft Students Help Make More Dextrous Robots

By heleen / On Aug.27.2015 / In / Width

Thursday, August 27, 2015

Students from Delft University of Technology (TU Delft) working at Harvard University have helped develop a new type of soft inflatable actuator that can be used to make robotic movements more fluid. Their results were published in the online journal PNAS Early Edition of Monday 17 August.

Robots are becoming increasingly more dextrous in their movements and their ability to grasp objects. Today, the components responsible for these motorics are often soft, inflatable segments known as fluidic actuators. Yet in many cases these components still need a lot of air or water to change shape, making them large, slow and awkward. Now a team from Harvard University has developed a new soft actuator without this drawback.

Johannes Overvelde, a TU Delft graduate and now a PhD student in the Bertoldi Group at Harvard, led the research. “Last year I worked on this project with two MSc students from TU Delft, who came over to Harvard on research placements: Jonas D’haen and Tamara Kloek. They conducted experiments and helped implement an algorithm to predict the actuators’ behaviour.

“In our research,” Overvelde explains, “we connect fluidic segments in such a way that an interplay between their non-linear response results in unexpected behaviour. Certain combinations of these interconnected segments can result in fast-moving instabilities with negligible change in volume.”

These instabilities in turn produce major changes in the internal pressure, shape and length of the segments, and the pressure they exert. For example, one combination suddenly lengthened the actuator. Another caused the entire volume to transfer from one segment to the other. These rapid movements can be triggered by very small changes, such as adding 1 ml of water to produce an internal volume flow of 20 ml.

“If we can bring all these instabilities under control,” says Overvelde, “we could make soft robots able to move quickly without requiring a bulky fluid supply or pump. The beauty of these individual segments is that they are easy and cheap to fabricate from off-the-shelf materials. Yet when you connect segments, you produce soft actuators with very complex behaviour.” The next step, he adds, is to test the concept in soft robots.

More information

Publication: “Amplifying the response of soft actuators by harnessing snap-through instabilities”, Johannes T. B. Overvelde, Tamara Kloek, Jonas J. A. D’haen and Katia Bertoldia. PNAS Early Edition, published online before print on 17 August 2015;

Press release: “Controlling the Uncontrollable”, Harvard University;

Film: Controlling the Uncontrollable: A New Soft Actuator, Harvard University;

Website of Johannes Overvelde: