Session: 03-15-04: Smart Manufacturing and Robotics for the Future IV

Paper Number: 173800

Spatially Programmed Structures for Shape Morphing and Torque Transmission in Soft Robotic Systems 

As robotic systems transition from rigid-bodied architectures to soft, deformable forms, maintaining structural flexibility while achieving meaningful force output, precision, and durability becomes a central challenge. Soft robotic systems must be compliant enough to safely interact with their surroundings, yet robust enough to perform functional tasks that often require force transmission, directional control, or complex shape morphing. Grayscale digital light processing (g-DLP) 3D printing offers a promising solution by enabling the fabrication of monolithic components with spatially programmed mechanical properties. This technique allows for the creation of parts with varying stiffness in a single print, eliminating the need for multi-material systems or post-processing steps, and paving the way for more sophisticated soft robotic actuators. In this work, we demonstrate a series of bellow-type soft actuators printed entirely using g-DLP, with precisely designed distributions of soft and stiff regions. These spatially patterned stiffness profiles enable distinct deformation behaviors tailored to specific actuation requirements. In one design strategy, stiff segments are localized to limited circumferential sections of the bellows—typically spanning 30° to 60° of the circumference. When actuated under vacuum, the bellows collapse preferentially in the softer areas, resulting in controlled, directional bending. By varying the angular placement and span of the stiff segments, we achieve a wide range of shape morphing behaviors, including both planar bending and complex 3D deformations. This strategy allows for directional actuation without requiring additional mechanisms or materials. In a second approach, soft and stiff regions are alternated axially along the length of the bellows in a ring-like configuration. This arrangement maintains flexibility for bending motions while introducing a substantial resistance to torsion. As a result, the actuator is capable of transmitting torque along its length while remaining compliant in other degrees of freedom. This behavior is particularly useful in soft robotic arms that must accommodate environmental interactions with passive compliance, yet still perform actions such as twisting or rotating objects. These two design strategies illustrate how spatial stiffness modulation—enabled through grayscale printing—can be harnessed to create multifunctional behavior in soft actuators. The ability to tailor mechanical properties at the voxel level provides unprecedented control over actuator performance and eliminates the complexity of traditional assembly-based fabrication methods. Our findings highlight the potential of g-DLP in enabling next-generation soft robotic components that combine the adaptability of soft materials with the mechanical sophistication needed for real-world tasks, ranging from navigation in constrained environments to delicate manipulation and force transmission.

Presenting Author: Farzad Gholami Toyota Research Institute of North America

Presenting Author Biography: Farzad Gholami is a Ph.D. student in the George W. Woodruff School of Mechanical Engineering at Georgia Institute of Technology. He is currently a co-op at Toyota Research Institute of North America (TRINA). His academic background is in Materials Science and Engineering, with a focus on polymer processing, polymer synthesis, and additive manufacturing of soft materials.

Authors:

Farzad Gholami Toyota Research Institute of North America
H. Jerry Qi Georgia Institute of Technology
Umesh Gandhi Toyota Research Institute of North America
Yuyang Song Toyota Research Institute of North America