Dec 17, 2014 | By Simon

Back in May of 2013, MakerBot published a YouTube video on their 'Robohand' 3D printed prosthetic hand. For many, the video was a first for seeing the true potential of 3D printing when it comes to manufacturing low-cost hand and limb prosthetics.

The Robohand, which is both free and open source, was developed by South African carpenter Richard Van, who himself lost fingers in an accident. The 3D printable prosthetic hand has helped those in need beyond just the articulating nature of the hand design itself; the low-cost of manufacturing nearly obliterates the existing high costs of other prosthetic hands that can costs tens of thousands of dollars.

More recently, the University of Victoria's Biomedical Design and Systems Laboratory has been exploring ways in which they can build off of similar 3D printed prosthetics hands and upper limbs by redesigning more complicated, non-3D printed prosthetic hands to aid those in need in developing countries.

As part of a new project from the Laboratory, researchers are using 3D printing to look at how the interaction between a user and their prosthetic hand can be highly intuitive, minimally invasive and appear cosmetically natural while being affordable to deploy to countries in need.

Professor Nikolai Dechev, head of the University of Victoria's Biomedical Design and Systems Laboratory, is leading the effort towards creating these fully-functional, grasping hands using additive manufacturing methods.

Dechev's UV research program, which at its core, is centered on electro-mechanical system design and its application to biomedical equipment and sensors, wants to create a hand that is able to last beyond 250,000 open and close 'grasping' cycles and is also 3D printable.

While current solutions for those in need include metal graspers and hooks, the goal of the 3D printed hand deployment project is to design and deliver a final prosthetic that meets certain criteria. Among them, the project has outlined the following:

1) Adaptive grasp: The ability of the fingers to conform around the shape of an object held in the hand. As the hand closes around an object, the four fingers and thumb will flex (curl) inwards independently of each other and approximately conform to the shape of an object being grasped. The grasp of irregular objects (cube, tool, ball, etc...) will all result in a different grasps, even based on orientation within the hand.

2) Ease of control for amputee: Control of the device must be easy and intuitive. Control must be robust to ensure desired action, and to prevent/minimize unwanted operation. Sensor design for bio-signals is integral with the control strategies being researched.

3) Feedback to the amputee: Presently, amputee users of conventional prosthesis rely on visual feedback and other indirect methods to manipulate objects. An important direction of our research is exploring new methods to provide feedback directly to amputees (see biomedical systems page), such as stimulators.

4) Cosmetic appearance: The natural appearance of a hand prosthesis is highly important, in terms of both static (stationary) and dynamic (moving) appearance. Our designs strive for natural, anthropometric form.

5)Scalable design: Prototype prosthesis designs are sized for an average 11 year old child's hand. Ideally, weight should also be equal or less than a similarly sized conventional prosthetic hand. By aiming for this objective, the design becomes scalable for larger/older users.

6) Low power design: Power consumption has a direct impact to the utility of a prosthesis, and must be minimized.

7) Robust design: The prosthesis must be strong, durable and be capable of sufficient grip strength to accommodate the the required tasks. In particular, the tri-digital (three fingered) pinch force should be at least of 50+ N.

8) Low cost, easy maintenance: The prosthesis must be designed for low-cost fabrication to ensure wide-scale adoption. Maintenance should be easy and infrequent, expected after 250,000 open/close cycles.

While their current iteration, the TBM 1-DOF has proven to meet these requirements, its construction is not based on 3D printed methods and the next goal for the team is to redesign the hand for being able to reproduce quickly and accurately using 3D printing. This includes the finger joints, the palm and various internal mechanisms.

The final hand, like the Robohand, will be waterproof, free of costly electronic components, and will be able to be easily replicated.

You can find out more over at the University of Victoria's Biomedical Design and Systems Laboratory here.


Posted in 3D Printing Applications

 

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