Maryland Robotics Center Research Symposium 2024

Title: Liquid Metals for Soft Robotics

Abstract: This talk will discuss the use of liquid metals for soft and stretchable electronics and devices (1) . Alloys of gallium are noted for their low viscosity, low toxicity, and near-zero vapor pressure (2) . Despite the large surface tension of the metal, it can be patterned into non-spherical 2D and 3D shapes due to the presence of an ultra-thin oxide skin that forms on its surface (3) . Because it is a liquid, it can be patterned in ways that are truly unique for metals, such as printing, injection, and selective wetting. The metal is extremely soft and flows in response to stress to retain electrical continuity under extreme deformation (4) . By embedding the metal into elastomeric or gel substrates, it is possible to form soft, flexible, and conformal electrical components, stretchable antennas, and ultra-stretchable wires that maintain metallic conductivity up to the strain limits of the encasing material. In addition to discussing the advantages of these materials for electronics, this talk will focus on recent work from our group to utilize and understand the behavior of liquid metal. For example, it is useful for tactile sensors. The sensors detect touch from changes in capacitance. By using soft composites consisting of liquid metal particles dispersed in elastomer, it is possible to increase the dielectric properties while using ultra-soft materials (5) . Thus, the sensors are very sensitive to touch. Furthermore, liquid metals can form hermetic seals in soft devices. Normally, soft materials such as elastomers are highly permeable to gas, making them poorly suited for devices that contain gas or electrolyte, such as batteries (6) . Recently, we showed that liquid metals can form perfect barrier materials that are soft and stretchable. Finally, recent work shows it is possible to use liquid metal to actuate soft robots using either surface tension to exert forces on surfaces (7) or electrochemical formation of gas to expand pneumatic chambers (8) . Combined, these advances have exciting implications for soft robotic materials.

Michael Dickey received a BS in Chemical Engineering from Georgia Institute of Technology (1999) and a PhD from the University of Texas (2006) under the guidance of Professor Grant Willson. From 2006-2008 he was a post-doctoral fellow in the lab of Professor George Whitesides at Harvard University. He is currently the Camille and Henry Dreyfus Professor in the Department of Chemical & Biomolecular Engineering at NC State University. He completed a sabbatical at Microsoft in 2016 and EPFL in 2023. Michael’s research interests include soft matter (liquid metals, gels, polymers) for soft and stretchable devices (electronics, energy harvesters, textiles, and soft robotics).

Title: Creating Soft and Stretchable Electromagnetic Devices for Soft Robotics

Abstract: Magnetic actuation is the most widely used actuation approach in conventional robotics due to its linear response with current, ease of generating large forces and low required voltages. Electromagnets are however challenging to make soft and stretchable, leading to other technologies such as pneumatics being far more common in soft robotics. In my talk, I will be discussing all aspects of creating stretchable and flexible electromagnetic devices and their use in soft robotic systems such as fluidic pumps and magnetorheological grippers. I will focus on the use of room temperature liquid metals and stretchable magnetic materials to enable stretchable electromagnets and maximize responsiveness to magnetic fields. Using these approaches, we demonstrate new records in performance, from a flexible solenoid pump with flow rates up to 320 mL/min to a magnetorheological composite capable of 70x stiffness tuning and 20 ms response time.

Nathan Lazarus has worked extensively in areas ranging from mixed signal electronics to MEMS fabrication, with his Ph.D. at Carnegie Mellon culminating in 2012 with the demonstration of the highest recorded fractional sensitivity to date for a capacitive chemical sensor topology integrated with CMOS electronics. Before joining the University of Delaware in Aug. 2022, he was a researcher at the US Army Research Laboratory with research focused on stretchable power systems, 3D printing and soft robotics. He has authored/co-authored 66 refereed journal articles and several book chapters, and has 21 patents awarded or pending. He has received numerous awards including ARL’s Early Career Award, ARL’s Honorary Award for Engineering and the Rookie of the Year Excellence in Federal Career Award (Gold) from the Baltimore Federal Executive Board. In 2019, Dr. Lazarus was selected for the Presidential Early Career Award for Scientists and Engineers (PECASE), the highest honor given by the US government for researchers beginning their independent research careers.