The experience in BionIT Labs: turning an internship into a job with a research work on the prosthetic finger

I would never have said that in March 2018, while I was following an optional class at the Polytechnic of Bari, I would have met a young CEO of a startup. Giovanni Zappatore, my former mentor, would have welcomed me three years later in his determined team, allowing me to become part of the amazing experience named Adam’s Hand

Together with Professor Giulio Reina, he proposed to me a thesis work innovative and motivating at the same time, which then became the core of the project that I will briefly tell you about, aimed at creating a prosthesis for partial finger amputation.

My research work

Partial hand loss comprises the majority of all upper extremity amputations and may involve the loss of one or more fingers.

The development of a prosthetic finger or partial hand must necessarily have as its foundation the anatomical study of the human counterpart allowing the complete recovery of the natural functions of the latter’s residual limb: firstly grasp and aesthetics later.

The study of the state of the art has immediately underlined the difficulties linked to the achievement of this goal: the hand – and therefore also the fingers – are compact but robust parts of the body, and at the same time characterized by a high degree of dexterity in carrying out the numerous daily activities that characterize our life. These characteristics are made possible by the presence of tendons, which transmit the movement of the forearm muscles to the joints present between the phalanges of the fingers.

How many types of prosthetic fingers?

The objective was to generate a solid knowledge base about the multitude of systems adopted, using it as starting point for the following prototyping: no matter if they were under development, commercially available or if they belonged to different kinds of prostheses.

This research was published in the MDPI Robotics Special Issue “Feature Papers 2020″journal, here you can learn more at this link.

The first is the case when a customer chooses not to use  a prosthesis, that may be a cost-effective option, although it’s important to consider the drawback for overusing your sound side, as the risk of running into problems with body symmetry, alignment and posture.

Without considering this, there are five prosthetic options for partial hand prosthetic rehabilitation:

  1. Passive prosthesis: mostly cosmetic prosthesis, without an active grasp and release, maybe a back-drivable trigger motion).
  1. Body-powered prosthesis: this prosthesis is directly controlled by users’ wrist or the remaining portion of their hand. There are three types of body-powered prosthesis for partial hand amputees:
  • Joint-driven
  • Cable-controlled
  • Wrist-driven
  1. Electrically powered prosthesis: It’s controlled by sensors based on electromyography and electrical motors.
  1. Activity-specific prosthesis: it supports the achievement of specific functional goals.
  2. Hybrid prosthesis: it combines elements of two or more prosthetic options with the aim of improving a person’s functional ability.

Voice of Customers: the importance of user experience

The key point for a good system design is to identify what are the customer’s problems and requests, and the technical requirements implemented to fulfill them.

Through an in-depth reading of 374 between patents and research articles, the criteria for the evaluation and categorization of the performance of the mechanisms at the basis of finger and partial hand prostheses have been obtained.

They can be divided into functional or grasp and physical features.

Grasp FeaturesPhysical Features
– Shape-Adaptivity
– Pinching Motion
– Stability
– Force Isotropy
– Workspace
– Stiffness
– Bond and Adjustment
– Accuracy
– Time
– Weight
– Number of Phalanges
– Compactness
– Design Flexibility
– Biocompatible
– Appearance
– Manufacturing Process
– Noisiness

The more these features are implemented the more the project difficulty/complexity increases. So it’s mandatory to find a compromise in order to achieve a satisfactory deal. 

Examples of cable-guided prosthesis from Masahiro, I.; Hiroshi, Y. Prosthetic Finger. J.P. Patent 146998A, 20 August 2015 (6) and Traverso, S.; Lince, A.; Laffranchi, M.; de Michieli, L.; Boccardo, N. An Underactuated Prosthetic Hand. W.O. Patent 215577 A1, 14 November 2019 (7)

Definition of the requirements of our prosthetic finger

We decided to design our prosthetic finger with the following requirements:

  • Body-powered prosthesis: in order to obtain a device with reduced weight and bulk volume, while it resembles as much as possible the natural extension of the user’s residual finger.
  • Underactuated prosthesis: if it uses fewer actuators than the actual number of DOFs. This feature enhances an easy control and a shape-adaptive grasp, as for Adam’s Hand.
  • Isotropic force mechanism: it allows to obtain stable grasp, avoiding ejection fenomena.
Examples of underactuated prostheses from Esempi di protesi sottoattuata da George, L.E. Artificial Finger. U.S. Patent 2867819, 13 January 1959. (8) and Li, G.; Jin, J.; Deschamps-Berger, S.; Sun, Z.; Zhang, W.; Chen, Q. Indirectly self-adaptive underactuated
robot hand with block-linkage mechanisms. Int. J. Precis. Eng. Manuf. 2014, 15, 1553–1562 (9)

The design process

After the definition of main features of the prosthetic finger, the next steps are:

  • a primary stage where a qualitative dimensional synthesis is performed with the help of already-known mechanisms aiming to improve the efficiency and to reduce complexity of the mechanism.
  • it follows the implementation of the analytical model that verifies the key variables of the mechanism
  • kinematic model able to predict and calculate through equations all the changes of variables value during the prosthesis’s motion.
  • dynamic model in order to evaluate internal and contact forces
  • CAD design that allows us to verify the assembly performance and compliance while evaluating the best wearable solution.
  • 3D prototype in order to check its bulk volume, aesthetics and function.

My adventure in BionIT Labs goes on!

In BionIT Labs I still continue the development activity of my thesis project, in parallel with the activities related to Adam’s Hand, with the aim of creating a product that has all the characteristics to be included in the BionIT Labs product portfolio and therefore be launched on the market.

Immagine 3

6 months after my entry into BionIT Labs, I’m convinced that the University can in most cases provide the tools of the trade, but to understand how these should be used it is essential to associate them with constant training, which is possible to experiment only in the workplace. Learning becomes even easier if you work in a stimulating and dynamic environment such as BionIT Labs.

And so I can say that a circle has closed, although I am sure that the in-depth studies in this area can give rise to an infinite spiral of research and development at the service of our final goal of “Turning disabilities into New Possibilities “.

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