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Senior finds gripping thesis problem

David Rodriguez has a 23-year-old friend with arthritis so painful that sometimes she can't open her front door. So when Mr. Rodriguez, a senior in mechanical engineering, was looking around for a thesis topic, his friend said, "Why don't you invent something that can help me?"

Six weeks later he produced the DR Grip, a machine powered by carbon dioxide that slips onto the arm and allows an individual to grasp, pull and turn with great strength though the forces applied with the hand are very small.

"With this device, a person who has almost no power at all in the fingers can grip with enormous force," said Ernesto Blanco, adjunct professor of mechanical engineering and Mr. Rodriguez's thesis advisor.

The DR Grip (so named for the inventor's initials) could also be successful commercially, Professor Blanco said, because it was designed to replace many of the self-help aids currently available for arthritis sufferers, and it could be relatively inexpensive to produce. Mr. Rodriguez estimates that the machine could be manufactured for about $80.

Last week the Department of Mechanical Engineering recognized Mr. Rodriguez's work by awarding him first place in the Luis De Florez Award competition. The award, which comes with a cash prize of $1,800, is for "outstanding ingenuity and creativity in design."

Rheumatoid arthritis, the most common form of arthritis and the form for which Mr. Rodriguez designed his machine, affects some 3.6 million adults in the United States. The disease primarily affects the small joints of the hands and feet, which become inflamed and swollen.

Because inflamed joints can be more easily injured, sometimes irreversibly, doctors recommend that people with arthritis try to protect them. "So you're faced with this problem," Mr. Rodriguez said. "You want to minimize the stress on your small joints, yet your hands are so important in daily activity."

As a result there are a number of self-help aids on the market that ease the pain associated with everyday tasks by reducing the loads, or forces, on the hands. They include dressing sticks to pull up slacks or zippers, and devices for turning water faucets and opening jars.

"It occurred to me that you could probably design something that would take care of most of these things," Mr. Rodriguez said. A single, versatile device could also be useful outside the home. "People don't want to carry a bag of devices around with them."

He went on to note that the DR Grip could fit in a large handbag. This is of special interest because three out of four arthritis sufferers are female.

Mr. Rodriguez also designed the DR Grip so that it is light (about two and a-half pounds, with potential to be considerably lighter) and easy to put on and operate. A user simply slips her arm into the device so that the hand curves naturally around a metal grip. Padded bars along the forearm stabilize the device, which is held in place with a Velcro strap.

By opening or closing her hand, the user then adjusts the device to the size of the object she wants to grasp. To lock the grip around the object, the user lightly presses a trigger with the index finger. This activates a system powered by a carbon-dioxide cartridge, the same kind of cartridge that's used in BB guns. (Mr. Rodriguez used a CO2 cartridge because it is very light and small.)

The force imparted by the device when the trigger is depressed is substantial. This writer used the DR Grip to pick up a small plastic cup, and the cup wouldn't budge when attempts were made to dislodge it with the other hand. (As a safety precaution, the device is instantly disengaged when the user moves her finger off the trigger.)

Mr. Rodriguez demonstrated the DR Grip by opening a door and turning on a faucet. He noted that because the device is stabilized to the forearm, "the loads associated with twisting or pulling are transmitted directly from the device to the forearm, upper joints and shoulder. So you're bypassing your fingers and wrist."

The DR Grip consumed most of Mr. Rodriguez's final semester at MIT. He dropped all but one class to pursue it. "The good thing about [the device] is that I may be able to really help people," he said. And what about his friend, who started all of this? Though she hasn't yet seen the final device, "she'll probably want to keep it."

A version of this article appeared in MIT Tech Talk on May 17, 1995.

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