High Tech, Soft Wear

Fall 2024
Silvia Cernea Clark

After a thankless career as the stuffing in couch cushions, foam unveils overlooked high-tech prowess that could make it a key material in next-generation soft-bodied robots and wearables. 

Rice engineers have shown that something as simple as the flow of air through the meshlike structure of open-cell foam can be used to perform digital computation, analog sensing and combined digital-analog control in soft, flexible wearable systems.

“In this work, we integrated material intelligence — the ability of materials to sense and respond to their environment — with circuit-driven logic using a surprisingly simple approach based on the flow of fluid through soft foams,” says mechanical engineer Daniel Preston, whose findings were recently published in Advanced Functional Materials.

Electronic control systems are not always a good fit for soft-bodied robots and wearables due to the nature of the materials involved and the design constraints they generate. Nonetheless, fluidic circuits — which rely on the flow of gas or liquid to perform analog or digital operations — have been traditionally designed in ways that mirror electronic circuits, i.e., by linking individual components via connecting elements. In soft robotics, such conventional circuit design architectures can result in devices that are heavier, harder to make, more expensive and failure-prone.

Our work at Rice is making real contributions across multiple fields, and I am glad so many of our students continue to do so, in academia, industry and even their own companies after training in our program.

Instead of conforming their design to these standard architectures, the researchers focused instead on the properties intrinsic to soft materials in order to maximize circuit design efficiency. Thus, pressure differences created by air flowing through the microscopic pores in foam sheets were harnessed to perform complex pneumatic computations and control tasks with a greater economy of circuit design.

The researchers also built foam-based fluidic resistors — devices that restrict airflow in pneumatic circuits, much like how electronic resistors limit current flow in electronic circuits. The resistors can be used to create two-dimensional pneumatic logic circuits that can be embedded in textile-based wearable devices.

“Wearable robotic devices could, for instance, provide assistance to users with mobility limitations, and building wearables out of textiles and powering them using compressed air can make them comfortable, lightweight, low-cost and unobtrusive for the user,” says Anoop Rajappan, lead author on the study and a research scientist at Rice during the course of the project.  

“Our work at Rice is making real contributions across multiple fields, and I am glad so many of our students continue to do so, in academia, industry and even their own companies after training in our program,” Preston says.

Daniel Preston is assistant professor of mechanical engineering in Rice’s George R. Brown School of Engineering. Anoop Rajappan is a mechanical engineer and assistant professor at Tulane University.