Case Studies

Soft Wearable Device for Thumb Rehabilitation

This case study describes the design of a wearable device for thumb rehabilitation, and is based on work carried out by Maeder-York et al. (2014)

Soft Prosthetic Hand for Amputees

This case study describes the design and construction of a soft prosthetic hand for amputees designed by a group of students in the Global Immersion Summer Program in India.

Soft Wearable Device for Thumb Rehabilitation

This case study describes the design of a wearable device for thumb rehabilitation, and is based on work carried out by Maeder-York et al. (2014)

Clinical Need

As discussed in the PneuNets glove case study, loss of grasping ability is a significant problem which negatively impacts quality of life in patients. It is possible to recover some lost function through intensive physical therapy, which typically involves the use of repetitive task practice (RTP). However, RTP requires a therapist to assist the patient and guide the hand through the correct motions. As RTP also needs to be performed continuously for several hours, this results in high therapy costs and limits the number of patients a therapist can see. 

The aim of the project described here was to develop a wearable device that replicates and restores correct thumb motor function for opposition grasp for patients with neurologically caused hand disabilities.

Solution

The design consists of a multi-segment fiber-reinforced actuator, mounted to a a conformable neoprene-padded aluminum attachment with Velcro straps, and tethered to a portable control system.

In order to determine the types of motion required from the actuator, electromagnetic (EM) trackers (3D Guidance TrakSTAR from Ascension Technology Corp.) were used to study the motion of the thumb during opposition grasp. This study yielded values for the amount of bending, twisting, and extension required of the actuator. Following the guidelines described on this page, the project team was able to design an actuator which, when inflated, would mimic the motion of the thumb.

In any wearable device design, methods of attaching to the patient are a non-trivial issue. In this project, one end of the actuator was mounted to a conformable aluminum plate which could wrap around the patient's hand. Velcro straps along the length of the actuator attached it to the patient's thumb. The full assembly was sewn into a glove.

The portable control box for the device was a modified version of the Soft Robotics Toolkit control board, as described on this page.
This video gives a demonstration of the final device in operation.

Soft Robotic Prosthetic Hand for Amputees

This case study describes the design and construction of a soft prosthetic hand for amputees designed by a group of students in the Global Immersion Summer Program in India.

 

Clinical Need

Diabetes, peripheral artery disease and trauma cause hundreds of thousands of upper limb amputations worldwide per year. For amputees, restoring the utility of a missing hand is a major factor in being able to do activities of daily living (ADLs) like eating, bathing and dressing themselves. Gaining the ability to do these basic tasks is extremely helpful to the patient achieving a higher quality of life. Current prosthetics including body powered and myoeletric devices give a lot of this function back to the patient, but can be tiring to use, expensive, stiff, or have a limited range of motion.

 

Solution

The team’s solution consists of 4 fiber reinforced bending actuators that mimics the index, middle, ring and little fingers. The thumb is an aluminum mechanism actuated by pneumatic artificial muscles.

The overall goals of the project were to design a soft prosthetic hand that was: cost effective, aesthetic, provided sufficient grip strength for ADLs, low maintenance, and light weight. The design of the hand was broken up into 4 separate modules: Thumb, Palm, Fingers, and Control. These 4 modules were determined to need to come together to into a few potential grip patterns that would be useful to complete ADLs, including pinching, open palm, pointing and a power grip.

The thumb design needed to be rigid and able to transmit forces in multiple different orientations for the different grip patterns. To achieve these grip patterns, the thumb was designed as a hinged aluminum mechanism. For more information on the thumb's design and actuation visit the case study page under the Pneumatic Artificial Muscles section.

The four fingers consisted of fiber reinforced actuators fabricated exactly as laid out in this section. The four fingers were attached to a palm, which was a passive hinged mechanism. The students experimented with materials such as wood and acrylic before deciding on aluminum for the palm.

The fiber reinforced actuators were controlled by a version of the Open Source Control Board described on this site.

The following video shows the hand in action: