Smart Ring and Bracelet for Stroke Survivor Study
Role: Design Director and Head of Product at Formsense.
Stroke is the No. 5 cause of death and a leading cause of disability in the United States. A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or ruptures.
The most common types of disability after stroke are impaired speech, restricted physical abilities, weakness or paralysis of limbs on one side of the body, difficulty gripping or holding things, and a slowed ability to communicate. Early treatment and rehabilitation after stroke can improve recovery and many people regain a lot of function.
With the aim of discovering better and more effective treatment for patients, Formsense was selected to be the industry partner in a $2.5m NIH grant with Harvard Medical School, University of Massachusetts-Amherst with clinical trials at the Spaulding Rehabilitation Hospital to study the role and efficacy of upper limb sensors in monitoring and grading motor functions in stroke survivors.
Stroke is the No. 5 cause of death and a leading cause of disability in the United States. A stroke occurs when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or ruptures.
The most common types of disability after stroke are impaired speech, restricted physical abilities, weakness or paralysis of limbs on one side of the body, difficulty gripping or holding things, and a slowed ability to communicate. Early treatment and rehabilitation after stroke can improve recovery and many people regain a lot of function.
With the aim of discovering better and more effective treatment for patients, Formsense was selected to be the industry partner in a $2.5m NIH grant with Harvard Medical School, University of Massachusetts-Amherst with clinical trials at the Spaulding Rehabilitation Hospital to study the role and efficacy of upper limb sensors in monitoring and grading motor functions in stroke survivors.
In order to monitor movement in both upper limbs with enough granularity, we designed and manufactured a smart ring and smart bracelet for each limb with the following criteria based on the patient persona and product requirements:
- The rings and bracelets should fit a large range of finger and wrist sizes comfortably
- Rings/bracelets should be easy to put on/take off for someone with limited limb movement and dexterity
- Charging the items should be clear and easy
- Items should be able to withstand daily activities including washing hands, doing dishes and bathing
Design Direction
In addition to meeting requirements we focused on 2 core goals: making the experience seamless and easy for the patients and getting great data for the researchers. At the center of both of these goals is the idea of making our wearable interactions an easy habit - by making it easy for patients to wear our sensors everyday through habit we ensure researchers get more complete data. We relied on muscle memory and the idea of a "ritual" as a UX combo to create a habit.
The final design consists of:
In addition to meeting requirements we focused on 2 core goals: making the experience seamless and easy for the patients and getting great data for the researchers. At the center of both of these goals is the idea of making our wearable interactions an easy habit - by making it easy for patients to wear our sensors everyday through habit we ensure researchers get more complete data. We relied on muscle memory and the idea of a "ritual" as a UX combo to create a habit.
The final design consists of:
- A "nightstand station" that the patient sees first thing in the morning and last thing before going to bed, prompting them to put on/take off the sensors in a daily ritual they can easily follow and are visually prompted if they forget.
- 2 ring sensors with minimal volume and sized to the patient's finger, water resistant and clearly marked with hand (left/right) it should be worn on.
- 2 wrist sensors with adjustable elastic velcro straps for ease of use and comfort (no buckles, just pull and stick).
- A USB C cable and wall plug.
The charging design and CMF ensure patients always put the sensors on their corresponding limb by providing specific stations and assigning a color for each limb (white for right - a purposeful rhyme, and gray for left), connecting both sensors and the charging area to the corresponding limb. The constant picking up/putting down movements on the same side for each color-coded sensor aimed to minimize cognitive load and create muscle memory. We avoided using colors in case a patient is color blind. Due to the chosen manufacturing method (Multi Jet Fusion 3D prints) and minimizing post-processing for cost, we used black Nylon for the ring bodies and charger housing.
Development and Prototyping
Time was tight and our budget was low, so the team quickly designed, prototyped and tested the assembly in multiple iterations relying on 3D printing to quickly evaluate results and for low-volume manufacturing.
Time was tight and our budget was low, so the team quickly designed, prototyped and tested the assembly in multiple iterations relying on 3D printing to quickly evaluate results and for low-volume manufacturing.
The chosen configuration consists of a common "pod" shared between all rings and wrist devices containing all the electronic components. This simplifies assembly and allows the pod to be potted for water resistance.
An effortless and satisfying connection between the sensors and the charger is important. We tested multiple magnet strengths, sizes and locations to obtain the satisfying "snap" of a successful connection. The magnets also assisted the patients with limited dexterity in correct placement, since the patient only had to drop the sensors in the general location before the magnet took over and connected.
The video above shows our EEs testing the charging interaction. If a sensor is placed on the wrong limb charging area it will flash a red LED, prompting the user to place the sensor on the correct charging side.
A total of 100 rings and wrist sensors were manufactured with corresponding nightstand chargers, and have been used for successful studies at the UMass Advanced Health and Human Analytics (AHHA) Lab.
A total of 100 rings and wrist sensors were manufactured with corresponding nightstand chargers, and have been used for successful studies at the UMass Advanced Health and Human Analytics (AHHA) Lab.