GALCIT Colloquium

The rapid pace of development of new responsive and structural materials along with significant advances in synthesis techniques, which may incorporate multiple materials in complex architectures, provides an opportunity to design functional devices and structures of unprecedented performance. These include implantable medical devices, soft-robotic actuators, wearable haptic devices, mechanical protection, and energy storage or conversion devices. However, the full realization of the potential of these emerging techniques requires a robust, reliable, and systematic design approach. My talk explores the design of such structures through optimal design methods. By investigating pressing engineering problems which exploit recent advances in materials, mechanics, and manufacturing, we develop optimal design methods to realize next-generation structures.

First, we investigate the design of 3D printed soft responsive actuators. Recent developments in material synthesis and 3D printing of anisotropic materials, such as liquid crystal elastomers, have facilitated the realization of structures with arbitrary morphology and tailored material orientation. Thus, we look to optimize structure and material orientation for integrated structures composed of both passive and active materials. However, the manufacturing process constrains the design as extrusion-based 3D printing aligns nematic directors along the print path. We discuss the proper regularization in this setting and formulate the design with such constraints. We consider a variety of lifting actuators, where we realize manufacturable designs while also recovering the print paths.

Next, we explore electrostatic zipper actuators for wearable haptics. Here, a dielectric-filled pouch is sandwiched between flexible conducting electrodes. When voltage is applied to these electrodes, the structure zips, leading to large deformation and pressure increase in the filled portion. We formulate a novel mechanics model for these systems and develop an efficient and robust numerical method to simulate the actuation process. As the complex physics of such systems create challenges for intuitive design, we apply shape optimization techniques through the method of mappings. Our method navigates the interplay between zipping susceptibility and volume displacement, and we explore optimal designs for various geometric and loading scenarios.

Moving away from soft actuation, we briefly discuss the optimal design of structures for impact resistance. After developing an accurate and efficient computational model for structures undergoing plasticity and damage over a dynamic trajectory, we formulate this in an optimal design setting. As an example, we explore the trade-offs between strength and toughness to design spall-resistant structures undergoing impact.

Finally, we discuss extensions, open problems, and other areas where optimal design methodologies may be applied.