Electrosoft : soft electrostatic technologies for cutaneous interaction

Traditional robots use rigid materials that allow for precise fabrication and controls. However, soft robots have drawn considerable attention in recent years because they are inherently safe for human interaction. Although it is more difficult for soft robots to achieve large forces or precise motion control, they outperform traditional robots in certain criteria like being lightweight, human safe, and suitable for handheld or wearable devices. Therefore, many researchers have focused on these aspects and have developed soft, small, and lightweight actuators. However, this field still faces challenges in providing enough displacement and force in a compact package and in reducing power consumption. Electrostatic actuation is a promising solution for achieving compactness and low power consumption in soft robots. This combination of electrostatic actuation and soft robotic structures underlies the work presented in this thesis, which has applications in cutaneous interaction for humans and robots, namely haptics and gripping. For haptic display, the main challenges include miniaturization and obtaining adequate bandwidth to display stimuli of interest. I present two different applications that take advantage of the unique capabilities of soft electrostatic actuators. Cutaneous haptic feedback devices were developed to impart sensations to the fingertip skin in a teleoperated or virtual environment. First, I present a stackable electroactive polymer (EAP) actuator designed to actuate a small handheld haptic device. This device communicates the needle tip forces to physicians during teleoperated image-guided needle interventions. Tests confirm that the device is magnetic resonance (MR) compatible. Tests with human subjects explored robotic and teleoperated paradigms to detect when the needle punctured a silicone membrane. In each paradigm, users detected membranes embedded in tissue phantoms with 98.9% and 98.1% success rates, respectively. Second, I designed a miniature dielectric fluid transducer (DFT) that has a large strain and fast response. The actuators can be packed closely and controlled individually to create dynamic texture displays, suitable for active surface exploration with fingertips. The simulation results show that the width of the actuator can be reduced without affecting the performance, which is useful for miniaturizing the device. Tests with human subjects show that users differentiated simple bump patterns with a 98.8% success rate. In soft gripping, a challenge is to find ways to enhance adhesion, which depends on the area of contact between gripping surfaces. Again, I present solutions that combine soft robotics and electrostatic actuation to achieve a synergistic effect. I developed electrostatic gecko-inspired adhesive technology robotic end-effectors, particularly for two-armed mobile robots, to minimize their force and power consumption, and expand their ability to handle bulky objects. Tests show that (i) the hybrid of electrostatic and van der Waals adhesion surpasses each technology's separate performance, (ii) it reduces the force and power needed to manipulate large objects, and (iii) a wide range of shapes and surfaces can be handled with the hybrid adhesive technology. In summary, I developed soft electrostatic technologies that are MR-compatible, compact, lightweight, and have low power consumption. Using these principles, I designed and characterized different actuators to overcome specific challenges in haptics and gripping. In each case the combination of electrostatics and soft materials -- ``electrosoft'' technology, to coin a term -- match favorably with the requirements of soft, cutaneous human-robot interaction

Keywords: Mechanical Engineering.
Advisor: Cutkosky Mark R. 
Follmer Sean 
Okamura Allison