ISE researchers develop improved crutch using flexible robotics
ISE graduate student Gaurav Singh and Professor Girish Krishnan have created a new crutch that implements “flexible robotics” to reduce physical stress and improve mobility, in conjunction with colleagues in the Department of Mechanical Engineering.
The new research improves upon the Lofstrand crutch, a model where each crutch attaches to the forearm with a plastic cuff and has a horizontal handle for the user to hold. However, using the traditional Loftstrand crutch can result in hyperextension from putting significant stress on the wrist, potentially leading to carpal tunnel syndrome and other wrist issues.
The soft robotic device designed by Singh and Krishnan’s team have been developed to prevent these painful problems. Instead of a rigid, plastic arm cuff to hold the crutch in place, they instead have created a flexible sleeve made of soft pneumatic fiber-reinforced actuators that create a constricting motion using air pressure.
Singh explains that the sleeve, which is attached to the modified Lofstrand crutch, squeezes the user’s forearm with each step.
“It applies a constriction force around your forearm, and that transfers some of the load from the palm to the forearm, reducing the load on the wrist,” he says. By easing the stress put on the wrists, this new design could prevent hyperextension.
Soft and flexible robotics provide benefits over conventional “hard” robotics, according to Singh. The sleeve can conform to the shape of many forearms rather than needing specific designs for each individual, and users would have an easier time performing tasks involving wrist motion, such as turning a doorknob.
Krishnan cites inspiration from nature for the design of the sleeve. He provides examples such as a grapevine tendril or an octopus tentacle wrapping around a support. Similarly, the robotic sleeve features actuators that spiral around the forearm in a helical shape, providing a better grip.
“When the piston pump [is] compressed during crutch loading, one-way valves inside the piston chamber will force the air into a Pneumatic Elastomeric Accumulator (PEA) inside the crutch shaft,” their team wrote for the Design of Medical Devices Conference in 2017. “That collected and stored pneumatic energy [is then] used to inflate the sleeve orthosis.”
Because the crutch captures the energy needed for the sleeve, Krishnan describes the self-sufficient device as “energy-harvesting.”
The research is in its final stages, with human testing being done by a team at the University of Wisconsin—Milwaukee, but the project holds a greater meaning in the timeline of human-wearable technology where little successful research has been conducted.
“About five to six years ago there was talk about soft flexible devices in augmenting human motion and giving additional support, but there were no functioning prototypes,” says Krishnan. “Today, the success of this project paves way for more clothing-like devices that can be worn and give support to different parts of the body. This is certainly a seminal work in showing that perhaps all these visions can come true.”