Fabrication-Integrated Design Lab

Counter-bending is a bio-inspired passive behavior that has been observed in the whip-like flagella of many microorganisms and cells. Counter-bending beams passively bend toward and conform around applied forces. Counter-bending behavior is particularly interesting in soft robotic grasping as it offers passive adaptability to objects in contact. The mechanism behind counter-bending behavior has been proposed as models and inspired compliant grasper designs in previous works; yet, existing designs only realize 2D counter-bending, which limits the adaptability to one direction. 3D counter-bending fingers can expand their adaptability to objects with wider range of geometries, and the unique constraints enforced by the 3D counter-bending beam can also be exploited in other applications such as coupling mechanisms and underactuated underwater locomotion. However, a physical realization of 3D counter-bending beam has yet to be proposed. In this paper, we employ continuum topology optimization to search for a beam structure capable of 3D counter-bending. The topology optimizer 1) validates existing 2D counter-bending model, and 2) generates a 3D structure that provides insight into prototyping a 3D counter-bending beam. To validate the structure from optimization results, we prototype a 3D counterbending beam using inextensible wires and soft elastomers, and we assemble 3D counter-bending fingers into an underactuated grasper to demonstrate the adaptability to objects with distinct geometries enabled by the counter-bending capability.

This study introduces the low-volume core (LVC) fabrication method, which enables the monolithic molding of compact, complex, versatile, and intelligent soft robotic systems. This method uses thin and flexible thermoplastic sheets to mold internal chambers in soft fluidic actuators, valves, and circuits. The LVC fabrication method creates low-volume networks in soft actuators (LV-net actuators) that can be made with compact and complex geometries, enabling both low actuation volume input and multi-degree-of-freedom actuators. LVC fabrication can also be used for compact, completely soft, and monolithic logic components (valves with low-volume core, also called as LV valves) to provide directional resistance as well as a switching mechanism that enables fluidic logic in soft systems. The compatibility of the fabrication methods for both soft actuators and valves facilitates the creation of compact, integrated, and versatile soft robotic systems with embodied intelligence. This study introduces two examples of such intelligent soft robotic systems that integrate both LV-net actuators and LV valves to demonstrate capability for complex system fabrication.

In comparison to traditional glass casting, glass additive manufacturing (AM) presents an opportunity to increase design flexibility and reduce tooling costs for the production of highly variable geometries. While the latter has been extensively explored for masonry units, there is minimal research on the former for its viability to produce structural building components. This paper encompasses design, manufacturing, and experimental testing to assess the feasibility of using glass AM to produce interlocking masonry units for the construction industry. The glass 3D printer employed in this study is capable of printing a maximum volume of 32.5 x 32.5 x 38 cm – suitable for producing full-size masonry units. As part of this work, we discuss how to adapt design guidelines for glass AM to produce interlocking units. To evaluate fabrication ease and structural performance, three fabrication methods, Fully Hollow, Print-Cast, and Fully Printed, are compared. To compare the accuracy, repeatability, and structural capacity of each masonry unit, geometric analysis, surface roughness, and mechanical testing is conducted. Results varied by fabrication method, with average strength ranging from 3.64-42.3 MPa for initial fracture and 64.0-118 MPa for ultimate strength. Accuracy in print dimensions were < 1 mm with a standard deviation of 0.14-1.6 mm. Results demonstrated that Fully Hollow masonry units provide a more immediate path to implementation, while Fully Printed units have the potential to provide an entirely glass, transparent, and circular building component fabrication method.

This study investigates the feasibility of 3D printing with recycled glasses, focusing on comparing viscosity characteristics and extrusion behaviors of studio soda-lime glass, recycled soda-lime container glass, and recycled float produced window glass. Employing multiple methodologies, we analyzed the temperature-viscosity curves of these glass types, providing an understanding of their thermal properties in relation to 3D printing process and applications. We employed infrared (IR) thermography to calibrate the glass printer and gain insights into the characteristics of each glass type during extrusion, contributing to a deeper understanding of their printing behavior. We discuss the potential applications of this work in various fields, such as recycled glass architecture and mass product customization. This study contextualizes the use of different glass sources for 3D printing and discusses some of the manufacturing challenges of utilizing post-consumer recycled glass. Our findings open new avenues for customized fabrication with recycled materials, paving the way for innovative and sustainable practices with a larger library of materials for 3D printing technology.

One of the major challenges in the design and construction of soft-rigid hybrid systems is having robust bonding at soft-rigid interfaces. Soft robots tend to be compliant and adaptive but weak, while rigid robots tend to be strong and precise but uncompromising. Soft-rigid hybrid systems can provide a blend of both compliant interactions with environments as well as fast and precise body position controls. In this paper, we propose a fabrication strategy using flocking to achieve strong bonding between soft and rigid parts. Flocking is a fabrication method that bonds short fibers to fabrics or plastics. The fibers create a fuzzy surface texture on rigid components, which increases the surface area. In the context of soft robotic molding, flocked surface texture increases mechanical bonding between soft and rigid components and enables incorporation of rigid components with increased complexity or challenging placement that could be overmolded but not glued. In this paper, we investigate design parameters for flocking such as substrate materials, adhesives, and flocking materials; we recommend design and fabrication guidelines for the use of flocking to incorporate printed ABS and PLA components in silicone. To demonstrate the utility of flocking in a range of soft systems, we have fabricated several example soft systems with integrated components, including a pneumatic network (pneu-net) actuator, soft chambers connected to semi-rigid tubing, and a sensorized soft actuator. The performance of these demonstrations was comparable or exceeded that of silicone glues and allows for direct overmolding of complex structures, making flocking applicable and versatile in soft-rigid hybrid systems.