Our team is developing a powered hand orthosis to help stroke survivors regain their manual dexterity and independence.  It features a soft, flexible shell, rapid manufacturing through 3D printing, and active, intelligent control to help the user perform daily activities independently. This solution was developed within the structure of the NSF I-CORPS program, an intensive 7 week course emphasizing customer discovery for hypothesis testing and validating customer segments. The team conducted 145 interviews (55 via phone, 78 via video call, and 12 in person) to various customer segments related to the project.  These include neurologically impaired patients (stroke, Parkinson’s disease, multiple sclerosis, and ALS), caregivers, and medical providers (doctors, nurses, and therapists).  The team tested several hypotheses regarding the upper-limb struggles of neurologically impaired patients, and made several discoveries that informed the direction of the project.  These include a change in device structure from rigid to flexible, a change in functional focus from fine to gross motor skills, and expanding the customer segment to include ALS as a potential target market in addition to stroke. This very valuable experience taught the team the importance of customer discovery and value propositions, developing solutions to meet the practical needs of real people, and the structure and initial financial considerations of startup businesses. After the 7 week course, our team developed a prototype and obtained IRB approval for human subjects testing.

Stroke affects millions of people across the globe every year, particularly the elderly.  In the US alone, nearly 800,000 victims suffer strokes annually, and approximately 228,000 survivors end up with mild to severe upper limb impairment. 

Having a stroke is a debilitating, life-changing event.  Part of the brain dies, and the mind-body connection is lost.  To better understand this problem, the team interviewed stroke survivors and medical providers.  They emphasized lack of hand control, including difficulties grasping and opening, and instability.  This leaves the survivor dependent on others for even the most basic tasks.  And current medical devices are inadequate.  They come in limited sizes and either prevent motion or constrain the hand to unnatural movement.  Further problems emphasized by users include abrasion, discomfort, expense, and difficulty to don.  The customer discovery conducted revealed many valuable insights; most significantly, that most stroke survivors need assistance with gross motor movements and would prefer a soft device to a rigidly articulated one.  A customized, 3D printed soft orthosis could mitigate these problems, providing a better fit and more effective recovery.  Guided by the input and experiences of stroke survivors, caregivers, and medical providers, the team developed a set of design requirements for the orthosis: easy to don, therapeutic, power assistive, intelligent, flexible, portable, and affordable.

Over the life cycle of the project so far, the team has completed:

1)      Modeling the orthosis structurally in CAD

The orthosis is composed of 3D printed, opposing soft actuators, one for flexion (closing) and one for extension (opening) of the hand. An intended feature of the CAD designs is that they will be easily customizable based on previously determined mathematical parameters for various hand length and widths in order to fit a larger range of the population.  At this point, both actuator designs (flexion and extension) are complete for a testable prototype.

2)      3D printing major components and assembling a prototype

Designs for the modeled actuators have been 3D printed and internal air pressure applied to view the flexion/extension behavior and experimentally determine the optimal materials, profiles, thicknesses, and internal structures of the actuators.  The material of choice is TPU, a flexible thermoplastic polyurethane, which will improve comfort and reduce abrasion relative to other more rigid materials.  

3)      Testing the prototype to verify appropriate function

Preliminary testing of the 3D printed soft actuators has been completed as a benchtop setup.  The flexion actuator curls the fingers to grasp in response to internal air pressure, while the extension actuator straightens them to open the hand.  These functions can be seen in the photos included.  As the actuators are iterated to optimize performance, more testing will follow.

4)      Obtaining approval for human subject testing. 

The team has applied to the Internal Review Board (IRB) for human subject testing, and our protocol has been approved.  We look forward to this phase that will carry on to the future and provide valuable data for the benefits and improvements of this device to the stroke survivor population.

This next phase of human subjects testing could help prevent or reduce hand spasticity for neurologically impaired patients, enable them to regain or maintain their independence, and reduce hands-on time for caregivers and therapists.

Last Modified: 09/06/2022
Modified by: Eric J Barth