Need an Extra Thumb? The Third Thumb Project Uses 3D Printing to Change Perceptions of Prosthetics

Many people have, at one time or another, wished for an extra set of hands to do everything they need to get done, or to carry loads of items. Royal College of Art graduate Dani Clode might not be able to fulfill that wish, but she can give you the next best thing – an extra thumb. No, there’s no questionable genetic engineering at work here – just good old-fashioned 3D printing. (Okay, maybe 3D printing isn’t old-fashioned yet, but anyway.) For her graduate degree in design, Clode engineered a prosthetic thumb that gives wearers a bit of extra reach and dexterity.

Part of the idea of the Third Thumb Project, explains Clode, is to redefine what the word “prosthetic” means. We typically think of a prosthetic device as something that replaces a body part that has been lost, but that’s not always the case – a prosthetic can also be used to augment or expand.

“The Third Thumb investigates the relationship between the body and prosthetic technology in new ways,” she says. “It is part tool, part experience, and part self-expression; a model by which we better understand human response to artificial extensions. It instigates necessary conversation about the definition of ‘ability.’ The origin of the word ‘prosthesis’ meant ‘to add, put onto;’ so not to fix or replace, but to extend. The Third Thumb is inspired by this word origin, exploring human augmentation and aiming to reframe prosthetics as extensions of the body.”

The Third Thumb is a 3D printed device that wraps around the hand and attaches to a wristband, providing an actual third thumb on the opposite side of the hand from the natural thumb. The design of the thumb itself is based on live hinges, 3D printed from Ninjaflex filament, while the hand and wrist components – both of which contain motors – are 3D printed from Formlabs grey resin. The parts are connected by a bowden cable system made of teflon tubing and wire, similar to a bicycle brake.

“The human thumb has a really dynamic movement, the opposing movements working together to make the thumb more functional than a single finger,” says Clode. “The Third Thumb replicates these movements by using two motors pulling against the natural tension of a flexible 3d printed material…3d printing is the perfect medium for this project, as it enables quick prototyping, customised designs for various hand sizes and one-off production.”

The movement of the Third Thumb is actually controlled by the feet. Two pressure sensors are placed into the wearer’s shoes and connected to the thumb through a Bluetooth connection. With an extra thumb, wearers can extend their musical instrument-playing abilities, more easily grasp objects, or just improve their dexterity overall.

The design is currently in the working prototype stage, and Clode envisions two possible design aesthetics for the device. The “tool aesthetic” is designed to look functional, with a design that combines the look of a watch, a power tool and a fitness tracker. The “kinetic jewelry aesthetic” is a more designer look, inspired by the appearance of a tattoo – it looks more like jewelry, yet still serves the same function.

“The Third Thumb aims to challenge the perception of prosthetics,” Clode continues. “By extending the body I see it creating a similar trajectory for prosthetics as glasses or plastic surgery. Creating a shift from medical device to positive body image statement…When we start to extend our abilities, and when we reframe prosthetics as extensions, then we start to shift the focus from fixing disability, to extending ability.”

The design recently won the Royal College of Art’s Helen Hamlyn Award for Creativity, for which she and the other five HHA winners were each awarded £2,000 to help in further project development. Discuss in the Third Thumb forum at 3DPB.com.