Biomimetic Reaching Assist Device

Designers: William L. Hwang, Brian C. Yeh, Rahul Kak

Client Coordinator: Ellie Kehoe, Occupational Therapist

Supervising Professor: Larry Bohs

Our client was an active seven-year-old boy with TAR syndrome, which caused him to have very short arms. We developed a biomimetic reaching assist device (BRAD), enabling him to acquire, manipulate, and transport objects out of reach. Special features of BRAD include a TIG-welded aircraft aluminum harness, a horizontally folding tubular arm with a 40″ reach, plastic rubber-tipped pincers controlled by a bike brake, an acrylic tray to allow access to retrieved objects, foam padding on the shoulder straps and chest plate, a nylon cord enabling the client to control arm extension and folding, and a furniture-grade PVC docking station for device storage. With this device, the client can extend and retract the arm, perform fine-motor skills such as opening a cabinet, and retrieve a variety of objects including cups and snacks.

The client’s mother commented, “The reacher has greatly increased (his) ability to get things off of higher shelves. More importantly, it has helped him change his thinking to a more creative way of thinking about solutions to the limitations he has with his small arms. It was much more than just a piece of equipment for him, it helped him problem solve and think of how he can have more independence.”

The BRAD (Figure 1) consists of a modified drum harness (CSC1 Competitor Snare Drum Carrier, Pearl Corporation) with a hinged two-segment arm and fixed support member, both of 1″ square aluminum tubing, attached to the chest plate. The base arm segment and support member are TIG-welded to the aluminum chest plate and to each other. A butterfly-hinge, attached with rivets, connects the two arm segments.

A pair of rubber-tipped pincers, extracted from a commercial reacher (PikStik, Reid Industries), was modified for control by a bike brake/cable system and attached to the end of the arm. The bike brake lever is attached to the chest plate so the client can operate the pincer with his right hand. A nylon cord with three wooden balls is attached through guiding rings to the outer arm. The client pulls on the cord with his left hand to extend the outer arm, and releases the cord while tilting his torso to fold the arm inward using gravity. An acrylic tray, lined with black felt, is mounted to the support member. When the outer arm is folded inward, the pincers can drop an object on the tray, allowing the client to retrieve it.

A docking station, made from black and blue furniture-grade PVC, allows the client to suspend the BRAD by two wings attached to the shoulder straps of the harness, enabling him to mount and remove the device without assistance. The commercial shoulder harness padding did not provide a stable operating platform and comfortable fit. Open cell foam was contoured to our client’s upper body and attached to the shoulder straps with Velcro, which will enable replacement as he grows.

Figure 2 shows the client using the Biomimetic Reaching Assist. Cost of parts was approximately $680.

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