Introducing Soft Bionic Hands

Soft Prosthetic Hands Feature Image

Helping people understand bionic technology is part of our core mission. In this article, we examine the potential of soft bionic hands.

The Need for Improved Durability

As anyone who owns a bionic hand knows, durability is still a problem. Our User Satisfaction Surveys show that even recent versions of leading bionic hands continue to break at troublesome rates. This causes end-users a significant amount of frustration and inconvenience. It also affects their confidence in their prosthesis.

Most commercial bionic hands are currently made with rigid mechanical parts. Some companies have tried to improve durability by using stronger materials, such as titanium. Others have added cushioning and increased joint flexibility. Yet, the problem persists.

One possible solution is to use soft robotic design principles.

What Are Soft Robotics?

As usual, let’s start with a short video overview:

So, in essence, we replace all the rigid mechanical parts with soft material, which we then move using cables, hydraulics, pneumatics, electricity, or even chemical energy.

This makes sense for something that moves like a fish or snake, but what about a hand?

Applying Soft Robotic Principles to a Bionic Hand

Watch the first 1:18 of this video, which lacks voice narration but provides an excellent example of a soft bionic hand:

Here are the key design elements of this hand:

  • It is entirely 3D-printed, including any requisite structures/joints.
  • The fingers are controlled by an artificial tendon (i.e. small cable), as you can see in the following diagram:
X-Limb Finger Structure
  • The motors, microcontroller, etc. are placed in the palm:
X-Limb Motor, Controller
  • The fingers and in fact the entire hand are then enclosed in a 3D-printed membrane, which could make the hand both waterproof and dustproof:
X-Limb Finger With Membrane
  • The hand is controlled using two myoelectric sensors to open and close its thumb and fingers.
  • Only three core grips are supported; switching between the grips is achieved via a tactile button, not myoelectric control.
  • The hand is much lighter than all existing commercial hands, with a total weight of only 253 grams; this is about half the weight of a bebionic hand or an i-limb, and nearly 40 % lighter than a typical male natural hand.

Put another way, you are looking at a much lighter, more durable, greatly simplified design compared to most modern bionic hands, yet one that is still capable of successfully performing many daily activities.

Note, the hand featured in this section is the X-Limb, which you can read more about here. Also, all images in this section are from the scientific paper, A practical 3D-printed soft robotic prosthetic hand with multi-articulating capabilities.

Drawbacks of a Soft Bionic Hand

We do not believe that the following are permanent limitations of soft bionic hand designs, but here are a couple of limitations that we noticed with the X-Limb:

  • The grip force is much weaker than that of commercial bionic hands, especially in the power grip.
  • The potential sophistication of this design, at least its current version, is much less than what we’re seeing in new bionic hands due to hit the market in the next year or two, in particular the Atom Touch, the Esper Hand from Esper Bionics, and the C-Hand from Human Assistive Technologies (HAT) (articles on these two hands are pending).

Why Should You Care About This Technology?

One of our main goals at BionicsForEveryone.com is to make those with limb differences aware not only of their current commercial options but also of new options just around the corner. We do this because we recognize that many end-users are trying to plan cost-effective strategies for their future prosthetic needs.

This is particularly relevant with the X-Limb because it has a total parts cost of only $200 US not including the Quick Disconnect Wrist. Yes, you read that correctly: $200 US!

That’s not the total cost to the end-user, but let’s say that someone will eventually print out a custom X-Limb or another soft bionic hand for only a few thousand dollars. For those who cannot afford a typical multi-articulating hand, or maybe those who already have a capable Electric Terminal Device (ETD) but would like to be able to switch to a multi-articulating hand to wash the dishes or work on the computer, a low-cost soft robotic hand may be an ideal solution.

Related Information

Are you interested in bionic limb research? If so, see our complete selection of research articles.

For a comprehensive description of all current upper-limb technologies, devices, and research, see A Complete Guide to Bionic Arms & Hands.

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