Prosthetic limbs are expensive and complex, and they must be fit to each individual -- yet having a replacement for a lost limb can mean the difference between working and not, having a social life and not. So, Krista Donaldson and her team at the nonprofit design firm, D-Rev, are attacking the problem on several fronts, from re-engineering the moving parts, to exploring way-new materials that replace expensive titanium, to forming deep local partnerships for distribution and maintenance around the world.

It's the kind of work that D-Rev does; with a mission "to improve the health and incomes of people living on less than $4 per day," their motto is "Design for the other 90%." Taking a truly user-centered approach that could be summarized as "Listen before you build."

As Donaldson wrote in a paper for the WEF: "The world is confounded by difficult problems in healthcare that are ripe for innovative solutions. The information most needed for these solutions ... is readily available -- from the users. They need to be asked: How can we solve X? What is your experience with Y? Instead of focusing on asking people in developing countries to change their behavior, those of us who work in healthcare should sit up and listen to what they have to say."