Dr. Julius Dewald at Northwestern University’s Feinberg School of Medicine is experimenting with electromechanical devices for stroke rehabilitation.

The concept: a robot helps patients extend their arm more than they can now so the brain develops new pathways. Then the robot adds weight, making the limb heavier, so the patient can mirror a situation akin to living without the robot. The goal: robotic devices that cost less than $15,000, affordable for small clinics and some individuals.