Session: ASME Undergraduate Student Design Expo

Paper Number: 176178

Triangular Balloon Dielectric Elastomer Gripper for Gentle, Secure Grasping 

Most robotic grippers remain rigid, and it is not easy to pick up fragile or curved objects without damage. Soft robotics addresses this limitation by using compliant, deformable actuators that follow object shape. Among the most promising options is the dielectric elastomer actuator. DEAs are lightweight, highly elastic, and capable of very large strains under applied voltage, which make them strong candidates for soft grippers. Here we investigate balloon DEAs and propose a simple configuration: three thin membrane balloons placed in a triangular arrangement and directed toward a common center. When voltage is applied, Maxwell stress drives areal expansion and radial bulging of each membrane. The three balloons move inward, apply centripetal and well-distributed normal forces, and conform to the object without joints, linkages, tendons, valves, or external pneumatics.

Prior work on dielectric elastomer actuators has emphasized planar films, rolled tubes, and stacked multilayers. Balloon actuators for grasping remain largely unexamined. Our geometry leverages the quasi-isotropic expansion of each membrane to promote self-centering contact, enlarge the effective contact area, and suppress slip with minimal control overhead. The arrangement is inherently scalable through membrane diameter and thickness, and it is materials-agnostic with respect to elastomer and electrode technology. Because actuation is electrical rather than pneumatic, the device is quiet, cleanable, and straightforward to hermetically package. These attributes suit food handling, laboratory automation, and medical manipulation, where gentle interaction, washdown compatibility, and low part count are valued.

We develop an electromechanical model that couples a Yeoh hyperelastic strain-energy formulation with a linear viscoelastic term to capture time-dependent relaxation. Maxwell pressure links electric field, permittivity, pre-stretch, and thickness to membrane inflation, contact area, and normal pressure. We organize the design space using nondimensional groups, including an electroelastic index that compares electric pressure to shear modulus and a curvature ratio that captures initial geometry and pre-inflation. Parametric simulations produce design maps that connect voltage, thickness, and pre-stretch to attainable grip force, pressure distribution, and sensitivity. Early results indicate that the triangular array delivers stable contact pressure suitable for delicate objects while remaining within conventional DEA bias ranges in the kilovolt regime.

We examine key design tradeoffs and controls. Pre-stretch increases stability and strain margin yet shifts compliance and the onset of pull-in. Electrode patterning shapes the electric field and mitigates edge concentrations. Membrane thickness trades response speed for breakdown safety and sets the practical voltage window. Independent electrical addressing of the three balloons enables staged closure for gentle acquisition, passive self-centering during approach, and controlled release. Grasp state can be inferred from changes in capacitance or impedance, which provides low-cost feedback without added transducers. Safety concerns related to dielectric breakdown and charge retention are addressed through conservative field limits, smooth voltage ramps, and attention to insulation and interlock design.

A proof-of-concept prototype is under construction. Experiments will measure holding force, acquisition success across varied shapes and surfaces, endurance over repeated cycles, and stability under creep and relaxation. We will map safe operating windows, document failure modes, and benchmark against linkage grippers and soft pneumatic fingers of similar mass. The concept offers self-conforming grasp, one moving material, and predictive design tools for gentle, robust manipulation.

Presenting Author: Sandipon Mutsuddy The University of Memphis

Presenting Author Biography: I am Sandipon Mutsuddy, a junior in Mechanical Engineering at the University of Memphis, currently working on a project that focuses on a gripper based on dielectric elastomer actuators.

Authors:

Sandipon Mutsuddy The University of Memphis
Ayush Gupta University of Memphis
Vipin Agarwal The University of Memphis