Engineering Projects

Background and Clinical Relevance

One of the main goals of the hand rehabilitation lab is to help stroke survivors regain and recover hand function. Stroke survivors often struggle with everyday tasks which require fine motor abilities, specifically individual finger motion. The Bidirectionally Actuated Cable Glove (BAC-Glove) is a hand exoskeleton designed to drive independent flexion and extension movements of each finger. Linear actuators affixed to a splint on the dorsal forearm are attached to rigid cables running through guides on the fingers. These allow the fingers to be individually pushed into flexion or pulled into extension. However, this design requires the subject to wear a glove which poses a few problems. The glove may not fit for every subject and more importantly stroke survivors often struggle to wear a glove since their hands are often in a continuously flexed resting posture.

My Research

My work has been focused on helping to design the “Clip Glove” which utilizes convenient individual finger attachments for each finger segment rather than a glove. This design allows the subject the same functionality as the BAC-glove with a much easier process to wear the device.

The main challenge has been designing an attachment method which is universal and can be used for any subject with any finger dimensions.

The first iteration of the “Clip Glove” involved a set of clips which are worn by the subject that are dimensioned to that particular subject’s finger geometries. I designed a method in which the subject simply needs to input their finger widths and lengths into a .txt file which then updates a series of SolidWorks files containing carefully dimensioned sketches. A set of custom clips can then be 3D printed for each of the subject’s finger segments. The linear actuators push on rigid cables which feed through guide paths that snap onto the tops of the clips. This solution works, however, it requires a lot of extra work to print and correctly size the clips for each subject which can take a long time.

My solution to this problem was a ring with an adjustable aperture size to accommodate any finger diameter. Similar to how a camera lens opens and closes, my ring mechanism contains six very small pieces which can open and close smoothly to change the geometry of the opening with the simple sliding of a pin. Small elastic dental bands are used to pull on the pin so that the mechanism fits snugly on the finger segment without sliding off when force is applied. The design and assembly of this mechanism were quite challenging considering the small features and level of precision required for fabrication. The upside of this design is that we only need to make these rings once and we can simply reuse them. Since they can be used for any finger sizes, there is no need to make a custom set for each subject that comes in.

After conducting some preliminary motion capture testing using the “Clip Glove”, I have found that my design works well! The rings constrain the finger segments correctly so that when the linear actuator pushes on the cable, the finger bends into flexion, and when the actuator retracts, the finger opens in extension.

The “Clip Glove” uses custom clips which are sized to a specific subject’s finger geometries. These clips eliminate the need for a stroke survivor to wear a glove, however, it is not practical to fabricate this set of custom clips for every single subject.

The original BAC-glove drives independent finger flexion and extension for stroke patients. This solution involves a glove which is difficult for stroke survivors to wear and is designed for one specific hand size.

Original BAC-Glove