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Student Innovation - The Prosthetic Finger Grips Challenge; from Rough Sketch to Reality

Alistair Bacchetti

A Little Bit About Me and My Project...

My name is Alistair Bacchetti and I am a third year Biomedical Engineering undergraduate at the University of Glasgow. For the past year and a half, I have been a committed member of Handprints e-NABLE Scotland. This is a student-led society at the University that produces 3D printed prosthetic hands for people with upper limb deficiencies, free of charge and with a particular focus on children. Since June 2019, I have been working on the Prosthetic Finger Grips Challenge. This voluntary design project focusses on the reverse engineering of 3D printed prosthetic fingers for the incorporation of flexible silicone finger grips. In this article, I would like to share my project's journey from rough sketch to reality and show how working towards this heart-warming goal has inspired me to develop the maturity and perseverance of a competent engineer. 

The newly developed fingers are reverse engineered and remodelled from fingers of the e-NABLE organisation's Phoenix V2 prosthetic hand (open source). The new models comprise two essential components:

1. The finger - displays a small cavity on its front face, in which the silicone finger grip is inserted and contained.

2. The silicone finger grip - a small injection moulded grip featuring a natural finger ridge pattern to increase grip and give the finger a more natural look. Can be popped in and out of the grip cavity with ease. 

'So, why is this an innovative project?' I hear you ask. For starters, this is the first voluntary design project to be completed at Handprints e-NABLE Scotland, uniquely exploiting 3D printing and DIY injection moulding to produce a range of prosthetic fingers with improved grip and interchangeable grip patterns. More importantly, the project aims to provide our recipients with a freedom to self-express through their prosthetic hand; a quality that I believe should be at the core of all prosthetic hand design. This quality is achieved through a selection of interchangeable grip face patterns which the recipient may swap and apply to their prosthetic fingers. This allows the complete customisation of finger grip combination to  suit the recipient's preference.

A Spark of Inspiration 

A spark of inspiration was all it took to fuel my design ambitions. I discovered this shortly after accepting the challenge. Low on ideas, I explored the society's Facebook page and stumbled across the post that would kick it all off. In the image before me, I saw one of the society's first recipients. It was a young boy holding up his new prosthetic hand, its surface decorated with the cheery faces of his favourite cartoon characters. Raising his new hand with such pride and confidence, I could imagine him thinking 'This is me. This is who I am. I am unique and proud!'. I thought to myself 'That's it. That's the feeling and effort I want to contribute to'. To design new finger grips was impressive, but to improve a child's life through my own innovation and creativity was such a powerful, moving thought. I wanted that thought to fuel every rough sketch, CAD model and prototype I produced, as well as drive me to persevere despite the challenges I may encounter. 

Phase 1 - Kicking Off the Creativity

So there I was, sitting at my desk with a pencil, an older finger grip used by the society and one thought racing through my head - 'How can I tackle this?'. This was the beginning of Phase 1; an info-gathering, brainstorming stage where project knowledge, sound research and creativity merged to fuel my earliest designs. Here, my main challenges were to:

1. Know exactly what our recipients think of the older finger grip designs.

2. Know how the older finger grips perform throughout their use.

So I set out on my research effort, asking fellow society members on recipient finger grip opinion. In addition to this, I undertook many hours of finger grip observation; viewing how well they attached, testing their grip on different surfaces and applying them to everyday life as if they were a part of a new fashion trend.

As my project knowledge and intentions developed, I found myself scribbling rough sketches and weighing up different design ideas. With a smorgasbord of research and several months of brainstorming under my belt, I sketched and pursued the idea that would develop to become my first solid prototype. 

My lesson from Phase 1 was acknowledging the power of clear communication in design projects. Whether it was through asking questions, presenting rough ideas to my peers or talking out loud to myself, clear communication was and still is the key to sharing, evaluating and improving my design ideas. 

Phase 2 - Bridging Between Design and Reality

Phase 2 filled a gargantuan portion of the project. Spanning from October 2019 to late May 2020, this phase oversaw the earliest stages of finger reverse engineering, right through to solid prototype production and application to the Phoenix V2 hand. I often met with the society's 3D printing technician to tackle my main question of Phase 2 - 'How can I make this work?'. It was from many hours of collaborative research that the idea of 3D printed injection moulding was adopted as the main method for grip production. 

It was a challenging 7 months for the project, during which I often found myself back at the drawing board, remodelling each finger type ('Long', 'Short' and 'Thumb') and testing out various models of 3D printed injection moulds. Despite such challenges, my ambitions did not diminish, leading to the following monumental steps in project development:

1. The complete CAD remodelling of each Phoenix V2 prosthetic finger and the creation of the 'Loop', 'Whorl' and 'Arch' finger grip face patterns. All were designed on Solidworks 2019. 

2. A complete Finite Element Analysis of all remodelled fingers and finger grips using the Solidworks FEA simulation package. Not only did FEA pinpoint areas of contact stress and indicate grip performance, it compensated for the absence of collaborative, physical prototype testing due to the COVID-19 lockdown. 

3. An extensive research of DIY injection moulding, flexible and biocompatible polymers as well as the establishment of a DIY injection moulding procedure using 3D printed injection mould cases and food grade silicone rubber. 

'If at first you don't succeed, try, try again' - the perfect summary of my lesson from Phase 2. Perseverance is the fuel of any design project. It is the ability to continue in spite of challenges; the courage to say 'I will keep going. I will overcome this regardless of what I face'. From returning to the drawing board to continuing the project throughout lockdown, perserverance has been a valuable, paramount quality I have strengthened throughout my Phase 2 endeavours. I will strive to continue strengthening this quality throughout my future design projects. 

Throughout the final stages of Phase 2, I could finally see my project bridging between design and reality. With my 3D printer churning out pearly white prototypes and injection moulded grips patiently setting in their cases, I sat back and reflected. 

A time of reflection was dawning on my project. My first solid prototypes were almost complete though I knew my project and ambitions could go so much further - I could not wait to act on this thought and take one step closer to my goals.

Phase 3 - From Rough Sketch to Reality, to Reflection 

Phase 3 kicked off as soon as I popped my first finger grip out of its mould case. This was it - the moment when all my effort, perseverance, passion and support merged to form my first prototype models. 

'So, what next?' I often hear my peers ask. For me, Phase 3 is a balance between project progression and self-reflection; an opportunity to decide on my next steps and reflect on my performance throughout the project. Since the beginning of Phase 3 in early June, I have progressed my project efforts in the following ways:

1. Sharing my ambitions - Passing my experience and advice to fellow students has been as fulfilling as completing the project itself. Throughout June, I created a series of social media posts showcasing my journey throughout the project and gave advice on managing each phase. This was an excellent, rewarding way to reflect upon and learn from my experiences throughout the past year. 

2. Inspiring my peers - Being the first project of its kind in Handprints e-NABLE Scotland, I have used my experience and project journey to inspire my peers. It is remarkable to see my passion spread amongst other members of my society and I will strive to continue doing so throughout my future design efforts. Already, my project has inspired a second grip design project in the society; a collaborative effort between myself and a fellow Biomedical Engineering undergraduate to improve palm grip on our prosthetic hands. 

3. Putting my designs to the test (literally!) - Following my social media posts, I have been contacted by e-NABLE prosthetic hubs in the Netherlands and Nepal, allowing me to share my passion, experience and design efforts internationally. From August 2020, I will be working in collaboration with the Nepalese hub to test my prototypes on recipient hands, as well as continuing my own efforts in this challenge at Handprints e-NABLE Scotland. I really look forward to this upcoming task as it may see the application of my design to the very cause that inspired my ambitions; improving finger grip, recipient confidence and self-expression.

Completing the Prosthetic Finger Grips Challenge has been an immensely rewarding experience, allowing myself to develop the maturity and perseverance of a competent engineer, whilst applying a deep passion for Biomedical Engineering and helping others to a generous cause. 

I am exceptionally proud to share my passions and effort through the 'Students -share your innovations!' competition and would like to thank DesignSpark, RS Grass Roots and yourself, the reader, for listening to my story. Wherever you are and whatever you are developing, I sincerely hope my journey throughout this challenge inspires you to exploit your creativity for a greater, generous cause and encourages you to be the best engineer you can be. 

Please find my prototype design overview video in the following youtube link. If you would like a quick summary of my project and prototypes, take a look at this video.


Handprints e-NABLE Scotland uses Facebook, Instagram and LinkedIn as its main social media platforms. Please use the following links to access our web pages and view my design project posts:

If you would like to contact me about this project or my involvement in Handprints e-NABLE Scotland, please do so through either of the following:

My LinkedIn profile

My academic email address - 

Third year MEng Biomedical Engineering student at the University of Glasgow, as well as a passionate volunteer at the Handprints e-NABLE Scotland prosthetics society. I have strong interests in 3D printing, CAD modelling and reverse engineering as well as medical robotics and rehabilitation engineering.

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