Smart pens to help control hand tremors

(Phys.org)—Approx­i­mately 12 mil­lion people in the U.S. are affected by uncon­trolled tremors as a result of neu­ro­log­ical dis­or­ders such as Parkinson's dis­ease. From but­toning a shirt to writing a note, uncon­trol­lably shaky hands make it dif­fi­cult to com­plete some of the most basic tasks that most of us take for granted, according to fifth-​​year engi­neering stu­dent Zac Sheffer.

His team's project to combat the problem was one of two win­ners in the fall semester's mechan­ical and indus­trial engi­neering cap­stone course com­pe­ti­tion. Under the direc­tion of asso­ciate pro­fessor Andrew Gould­stone, the group came up with two approaches to improving leg­i­bility and writing per­for­mance among people with tremors.

The team's pas­sive approach guides the hand without sensing tech­nology, according to group member Andrew Hickson. The active approach, he said, senses the char­ac­ter­is­tics of a tremor, sends the infor­ma­tion to a com­puter that cal­cu­lates an appro­priate response signal, and then imple­ments the response through elec­trical com­po­nents inside a pen.

Within these two approaches, the team designed three solu­tions, all of which focus on velocity-​​dependent motion damping. "This is key," said team member Diego Solano, "because we don't want to damp all move­ment, just the bit that's caused by tremors."

The stu­dent researchers needed a way to test their designs, but faced a road­block: Patient trials were not pos­sible because of both time and fea­si­bility con­straints. One team member, how­ever, Mariah Dellea, recalled her expe­ri­ence with post­surgery phys­ical therapy, which used elec­trical impulses to stim­u­late muscle activity.

Using a stan­dard, over-​​the-​​counter elec­trical muscle stimulation—or EMS—device, the team mem­bers sim­u­lated tremors in their own hands. Then they devel­oped a testing pro­tocol to ensure that the sim­u­lated tremors resulted in writing per­for­mance equiv­a­lent to that of patients. They also used the pro­tocol to com­pare writing per­for­mance with and without their devices.

"We needed some­thing safe and reli­able but also quan­tifi­able and repeat­able," Solano said.

With the test method in place, the stu­dents began imple­menting designs, focusing first on the pas­sive sys­tems. They devel­oped sev­eral cus­tomized, ergonomic grips, to sta­bi­lize the hand and make holding the writing instru­ment much easier, said team member Darren Mahoney. At the bottom of each, they imple­mented a mag­netic con­tact that inter­acts with a plate con­taining metal fil­ings in order to steady movement.

Another of Gouldstone's cap­stone teams devel­oped an instru­mented pen, equipped with six force sen­sors that can col­lect infor­ma­tion about grip ten­sion during tremors. The data could be useful in diag­nos­tics as well as a resource for phys­ical therapy clin­i­cians. This group used the other team's testing pro­tocol to ana­lyze the utility of their device. Using the EMS, they demon­strated that grip force during tremor increases three­fold over normal conditions.

Mem­bers of both teams have sev­eral research goals for next semester. Lauren Hess and Joseph Ranieri of the instrumented-​​pen team will con­tinue working in Gouldstone's lab on other projects. Mem­bers of the corrective-​​pen team plan to fur­ther develop their pas­sive system and will start work on the active sys­tems. They also hope to ini­tiate pilot studies with patients suf­fering from real tremors, rather than using the EMS to sim­u­late the disorder.