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Economy & Business

St. Louis inventor seeks to make a better hand for his friend

This article first appeared in the St. Louis Beacon, Aug. 2, 2012 - St. Louis resident Mark Stark is an inventor, who typically designs gas valves for furnaces, water heaters and dryers. Stark's friend Dave Vogt was born without a hand and has used a hand hook for many years.

Stark set out to create something better for this friend, and succeeded. His work will be featured on "Everyday Edisons" at 10 a.m. Aug. 5 on the Nine Network of Public Media.

Stark's plan involved a hand that worked like the hook but was much more functional, looked more human and was affordable. It has gone through about four generations, but it not yet ready to be put on the market.

The hook hand attaches to the arm; a cable stretches across the back and the hand is controlled by stretching the back muscles. Stark said he came up with an idea that works on the same principle as the hook hand and that would allow each finger to be opened.

The hand has 14 joints that act independently to control the fingers. Each joint has a spring that allows the fingers to close and shape themselves around an object, such as a ball or a glass. Unlike other prosthetic hands, Stark's hand can be interchanged with the hook and use the same cable.

Stark said the first prototype was put together with hardware parts and lots of glue. Vogt was his guinea pig throughout the process and helped him figure out the fingers and the length of the pulls.

The rapid operation and shaping feature make this hand different from other prosthetic hands, Stark said. He said the hook is pretty capable but it cannot grasp things as well and there are only three rigid fingers. His hand, he says, can move as fast as a real hand and do things such as throwing or catching a ball. Another benefit is that it is body powered.

Robotic hands, powered by batteries or motors are generally heavier and less durable, according to Stark. He also said they are typically more expensive, they wear out quickly and are complex. The price of Stark's hand should be comparable to the hook hand. He said both cost about $1,000. Robotic hands cost around $20,000, Stark said, and that is before the surgery to attach it.

"I hope that it is a viable alternative for a lot of people and that it helps them," Stark said.

Although the hook can do some things better, Stark said his invention is superior in social situations, as he believes there is a stigma attached to a hook.

"The hand gets positive comments," he said. "People don't get positive comments with a hook. People with hooks get looks and fear."

Now that the hand is being featured on "Everyday Edisons," a design team will continue developing the hand to make improvements, with some input from Stark. He says he hopes they keep it simple but try to make it look more human. He said he is a little concerned they might try to take the hand too far. He said he wants to get it out sooner so it can help sooner, but said he believes it will be a couple of years before it is on the market. 

In the end, Stark said, "I'm really hoping to get Dave a good, proper hand."

Josie Butler is a Beacon intern.

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