EaseGrip
Paper admitted to the ASSETS '23 Conference & Taylor & Francis Disability and Rehabilitation: Assistive Technology
This project aims to showcase the feasibility of a proof-of-concept that parametric software empowers occupational therapists in fabricating customized adaptations of assistive technologies to effectively address the distinctive requirements of individuals with hand impairments. The platform enables OTs to modify pre-designed models of utensil grips, serving as examples of ATs, based on individual's hand assessments, specific requirements, and health condition.
What is Assistive Technology?
Assistive technologies (ATs) enable individuals with disabilities to participate in activities of daily living (ADL) that would otherwise be unattainable for them.
What would OTs do?
Definition
So occupational therapist (OTs) assists individuals with mental, physical, or emotional impairments by prescribing, modifying ATs to develop, regain, or maintain the skills necessary for everyday life and working.
Why hand?
In individuals with hand impairments, reduced hand mobility and grip strength, attributed to aging and various pathologies, can have a detrimental impact on the performance of activities of daily living, ultimately restricting personal independence.
ATs can be acquired
However,
Current situation
through commercial off-the-shelf solutions or by tailoring them or everyday items to cater to specific individual requirements.
Nevertheless,
Materials used for adaptation making like foam, Velcro, tape, sponge, and popsicle sticks are not durable and can pose hygiene problems. While thermoplastics offer greater strength, they come with a higher cost and the risk of warping in high temperatures, such as inside a car.
off-the-shelf solution: it is hard to find devices that meet the personal needs of users. Because mass-produced assistive devices are primarily designed to meet the needs of the general population and may not be suitable for individuals with specific and unique requirements.
Therefore,
OTs often employ various materials such as foam, tape, Velcro, cardboard, string, thermoplastic, and sponge to customize off-the-shelf or everyday objects, aiming to improve the fit and enhance usability for individuals with specific needs.
💰 expensive & deformation under high temperature 🌡️
⚠️ not durable
💧 hard to clean
3D Printing
Affordable
Reproduceable
Durable
Effcient
Robust
CAD Tool is Hard to Learn
Opportunity
The opportunity is to develop an intuitive platform for OTs, facilitating the digital design of grips for 3D printing. This aims to offer a more durable and cost-efficient solution for AT users.
First Prototype Iteration
The first iteration is designed to provide OTs with a better comprehension of this type of tool, while also helping us in identifying the essential parameters.
Follow-up Interview
This interview is to sought OT's opinions about the interface and grip designs included in the first iteration. And affinity diagram was adopted to analyze data.
~ 50 mins | 5 participants
Grip design suggestions
Include more different types of grips.
Have easy-to-clean texture on the surface to provide sensory feedback.
Use of strap for better support.
Flared shape handle to prevent hand sliding off onto the spoon.
Outside dimensions, height, and the inside dimensions are the most important.
Add weight option for specific needs.
Using slider scale for easy visualization of the immediate effects on the display.
Specify the unit of measurement.
Interface design suggestions
Add a section to allow changing color.
Avoid technical jargon on demonstrating materials.
Design Requirements
Interface design requirements were outlined to detail the essential components needed.
Upgraded Prototype
Four Different Shapes of Grip
Four distinct grip shapes offer a diverse range of options to meet varied purposes and user requirements.
Three Distinct Textures
EaseGrip offers three unique textures designed to enhance grip through sensory feedback for individuals with reduced hand sensation. Each texture is crafted for ease of cleaning and visual appeal, ensuring functionality meets style.
Smooth Grip
Straight-line Texture Grip
Curvy Texture Grip
Real-Time Interactive Display
The display will reflect any changes in parameters and color on time. It also enables OTs to use their mouse or touchpad to drag or zoom for a detailed view of the grip.
Customization - Grip Color
By employing a color swatch, OTs can alter the grip's color and instantly see the rendered effects on the real-time display.
Customization - Grip Designs
Based on feedback from OTs, I have designed four different grip patterns to accommodate a wide range of needs.
Customization - Grip Dimensions
The dimensions are categorized into two sections: exterior and interior. The exterior part enables OTs to modify the grip's diameter and height to suit the patient's hand, while the interior dimensions are tailored to accommodate the utensils.
Before creating the grip, OTs are required to measure specific dimensions (A, B, C, E, and F). These measurements are correlated with the software's parameters to ensure precision in the design. OTs can also adjust parameters freely depends on the needs.
Customization - Grip Weight
OTs have the option to select the grip's weight as light (~95g) , medium (~180g), or heavy (~250g), depending on the patient's needs. This weight adjustment is achieved by changing the infill percentage of the filament during the 3D printing process.
Customization - Grip Material
OTs can select between flexible and rigid materials.
Flexible: Soft PLA, TPU (certain degree of TPU is dishwasher safe)
Rigid: PLA, ABS, PP (dishwasher safe), PETG (dishwasher safe), ASA (dishwasher safe)
Usability Test
12 participants | have certification of OTR/L | 2-30 years of OT professionals
Session 1
During the initial session, OTs had an opportunity to manipulate the computational tool and develop a customized adaptive grip that suits the user's needs. Prior to this session, participants were required to complete a hand AT user profile. This profile encompasses a comprehensive range of user-specific details such as age, gender, medical pathologies, occupation, various assessments (strength, dexterity, range of motion, sensation). OTs will also complete a SUS survey regarding the interface usability and semi-structure interview during this session.
Session 2
The follow-up session reconvened the participants from the prior session. OTs will try and evaluate the printed hand ATs in this session.
Quantitative analysis
System Usability Survey (SUS) Result
Upon computing the SUS scores for each participant, the mean score across 12 participants is found to be 78.96. Generally, scores exceeding 68 were considered as positive feedback. Consequently, a mean SUS score of 78.96 indicates that the users perceive the system as usable, intuitive, and satisfying, reflecting positively on the user experience.
Beyond My Expectation
Qualitative analysis
A Need
Self Explanatory
Usefulness of EaseGrip
An affinity diagram was utilized to organize and categorize the feedback provided by occupational therapists during the usability test. Occupational therapists have confirmed the effectiveness of EaseGrip, highlighting its necessity and ease of use.
Uniqueness of EaseGrip
Occupational therapists have also validated the uniqueness of EaseGrip, emphasizing its high degree of customization, cost and time efficiency, and the critical role of user engagement.
Cost & Time Effectiveness
Co-Design
Customization
Pros of EaseGrip Interface
Occupational therapists also pointed out the variety of grips, extensive parameters, intuitive interface, and real-time display as crucial features for their quick comprehension and everyday use.
Suggestions of EaseGrip Interface
Valuable insights and suggestions from different perspective are provided by occupational therapists.
Printed 3D Grips
Build-up grip tailored to specific pathologies, needs, and hand conditions were printed using the Ultimaker 3/5s printers.
Customizable
OTs Expressed They are...
User-centric
Easy to clean
Practical
Cost-effective
Inclusive
Thoughtfully designed
Design Guideline
Parametric Software
Adaptive Grips
Refined Interface
The interface has been refined based on feedback from OTs and an AT engineer at a local clinic, making it more visually appealing and user-friendly.
Selections are now highlighted for better visibility, while parameters like weight and material have been removed, as these can be adjusted directly in 3D printing slicing software based on available materials. The download process has been streamlined—OTs no longer need to access Rhino software to download the generated models. Instead, it's a simple two-step process: bake the model in Grasshopper and save it directly to their computer.
Additionally, I have filleted the edges of the hooks for enhanced safety and a more comfortable wearing experience.
3D printing parameters and material experiments
3D printing proficiency requires time and is not within OTs' expertise. Safety, durability, and hygiene are critical as OTs assess its potential. This part explores the performance and optimal settings of three common 3D printing materials — PLA, PETG, and TPU — using cylinders as adapted grips.
I tested each material's minimum, middle, and maximum temperatures, considering the wide temperature ranges specified. Costs vary: PLA and PETG are $0.022/gram, while TPU is $0.124/gram. I also evaluated layer heights, infill percentages, and wall lines to optimize print quality, weight, and strength. The prints were created on UltiMaker printers using Cura, with time, cost, and status recorded to visually classify key parameters for AT fabrication.
Polylactic Acid (PLA)
PLA is a versatile and affordable material known for its durability and safety. I used 2.85mm MatterHackers white PLA with a recommended nozzle temperature of 180-220°C. The results (Figures a-c) show that printing at 200°C provides the smoothest surface and uniform layer distribution. Although seam differences are minor, the 200°C sample exhibits more consistent seams. The top view (b) shows noticeable gaps at 180°C, while the sectional view (c) highlights a cleaner internal structure at 200°C with solid support and fewer adhesions. Higher temperatures, however, make adhesive removal more challenging and may produce sharp edges.
Polyethylene Terephthalate Glycol (PETG)
Thermoplastic Polyurethane (TPU)
PETG is a rigid, food-safe material known for its durability, thermal stability, and chemical resistance, outperforming PLA in these areas. The recommended nozzle temperature for PETG is 220-260°C. Figures d-f show that printing at 240°C produces the shiniest surface, while 220°C yields the smoothest finish. Higher temperatures create a more matte surface and slightly more pronounced seams. The top view (e) reveals the clearest top structure at 220°C, while higher temperatures cause more internal crystalline fractures. The sectional view (f) indicates that PETG has cleaner internal structures than PLA, but higher temperatures can increase internal wadding.
TPU is a flexible, elastic material with a soft-touch surface. The recommended printing temperature is 225-240°C. Figures g-i show that printing at 225°C provides the smoothest and cleanest surface with minimal wadding and well-defined layers. At higher temperatures, TPU becomes stickier, causing more dents and bumps on the top surface (h). The internal view (i) indicates increased wadding and slight deformation at higher temperatures. TPU’s internal structure is designed for flexibility and strength, accommodating bending better than rigid materials. Like PLA, higher temperatures make adhesive removal more challenging.
Layer height
Layer height significantly influences the quality and detail of 3D printed items. We tested layer heights of 0.1mm (fine), 0.15mm (normal), and 0.2mm (fast). The side view [i] shows that smaller layer heights produce smoother textures and surfaces, reducing seam unevenness. The sectional view [k] indicates that finer layer heights also minimize internal adhesions. However, while thinner layers offer better quality, they increase print time: 0.2mm took 32 minutes, 0.15mm took 41 minutes, and 0.1mm took 59 minutes.
Percentage of infill
Adjusting the infill percentage alters the density, weight, and robustness of printed items. We tested infill percentages ranging from 20% to 100% [l]. Higher infill percentages extend print times: 20% took 43 minutes, 60% took 58 minutes, and 100% took 87 minutes. Increased infill also raises material usage and cost: 20% used 6g of filament, 60% used 11g, and 100% used 16g.
Wall line count
The wall line count affects the mechanical strength of printed items. We evaluated 2, 4, and 6 wall lines [m]. More wall lines enhance strength but also increase weight, print time, and cost: 2 layers used 6g of material and took 42 minutes, 4 layers used 8g and took 51 minutes, and 6 layers used 9g and took 61 minutes.
Recommended Settings
The image to the right displays the grips printed using our recommended settings for PLA, PETG, and TPU. The infill percentage, layer height, and wall line count can be adjusted according to specific requirements, and the test samples were designed with time efficiency in mind. It is important to note that different printers and nozzles may require varying temperature settings.
Storyboard
The design steps for creating a 3D model of a desired hand grip.
After conducting a clinical assessment of an individual’s hand, OTs can begin the process by selecting the appropriate grip type. They can then customize the design by choosing different surface textures, colors, and other features. Next, they can adjust the parameters based on the individual’s hand measurements and the specific utensil to be used. Finally, they can specify the 3D printing options based on our recommended properties, including the device’s weight, material, printer set up, and download the file for printing.
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