Tuesday 31 August 2021

Inflatable prosthetic hand can pet a cat

This is an article for people interested in technology and people who have unfortunately lost both hands (hopefully very rare) and who want to stroke their domestic cat. Prosthetic hands are normally very expensive and quite heavy because they are made of metal and motors. Researchers at the Massachusetts Institute of Technology (MIT) together with engineers/scientists at Shanghai Jiao Tong University, China have come up with what appears to be a brilliant alternative. This is an inflatable prosthetic hand that can be controlled with the mind and is 20 times cheaper to make than the metal and motor variety.

Inflatable prosthetic hand can pet a cat and do lot more besides
Inflatable prosthetic hand can pet a cat and do lot more besides. Photo: MIT.

It picks up electrical signals through the wearer's arm. When the person imagines making a fist with their absent hand the prosthetic hand picks up the muscle signals and carries out the command.

It can do four types of grasps including making a fist, cupping the palm, pinching two fingers together and pinching three fingers together. In tests it could pour juice, shake hands, zip up a suitcase and most importantly for me stroke a cat!

Rather than using motors, the hand's movements are controlled and driven by a pneumatic system which inflates and bends the fingers. The pump which drives the pneumatic levers is worn around the wearer's waist.

The materials used are much cheaper and cost about US$500 (£364) which compares very favourably with the $10,000 for materials used in motorised hands.

It weighs 225 g (8 ounces) which also compares very favourably with the metal variety as it is a fraction of the weight. The prosthetic picks up signals from electromyography sensors at the point where the device fits the body. The sensors pick up electrical activity when a nerve stimulates the muscle. The fingers can be fitted with a pressure sensor so it can restore some sensation.

This last benefit may also be very useful to a cat owner because there is nothing better than feeling your fingers as they pass through the fur of your cat companion. They say that one of the best cats to stroke is the British Shorthair because the fur is very dense.


The researchers' work is published in the journal Nature Biomedical Engineering. During the research they found that the inflatable prosthetic was as good or even better than the conventional, rigid, commercially available bionic hand in carrying out functions such as stacking checkers, turning pages, writing with a pen, lifting heavy balls and picking up fragile objects.


Further, the device is very durable and has a 3D-printed palm to mimic a human hand. One volunteer was able to successfully shake a person's hand, touch of flower and pet a cat.

Source: The Times - thanks.

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