At least since the first four tennis balls were added to the legs of a walker, people have often found ways to tinker with their medical devices — often through small modifications or, in some cases, by fashioning their own devices completely from scratch.

Here are some examples of thoughtful people taking matters — and materials — into their own hands to meet their own and others' medical needs.

Agricultural prosthetics

Losing an arm to an accident or a war can be economically devastating for a farmer or agricultural worker. And yet traditional prosthetics don't always work well for planting, fertilizing, irrigating, and harvesting. Now there's a new crop of modular prosthetic limbs with attachments for various farming tasks and tools. The Farm Arm, for example, was developed this year by students at Northeastern University for farmers to operate different types of machinery.

Diabetes care in the cloud

Most glucose monitors require the parents of children with type 1 diabetes to be physically near their kids so that they can watch and test blood-sugar levels, injecting a dose of insulin as needed. But several parents figured out how to rig glucose monitors to send information to the cloud, where they can check their children's levels on smart phones. Their system, called Nightscout, lets these parents send their kids to field trips and sleepovers while still keeping track of their diabetes.

Solar sterilizer

Medical personnel need sterile instruments for safe gynecological examinations, prenatal care, and emergency births. But rural areas in developing countries often lack the reliable electricity needed for autoclaves, which use heat for sterilization. Enter the Solarclave. Made from common, locally available materials, including mirrors and a bucket, this sterilizer captures, traps, and concentrates heat from sunlight to sterilize instruments.

Helmet hearing

After a tumor rendered her deaf in one ear, artist Amelia Marzec learned that the hearing aid she needed would cost thousands of not-covered-by-insurance dollars. So she decided to build her own hearing device. Using a helmet, wires, small microphones, and amplifiers, she created Re-Wired, a device that uses bone conduction to route sounds to a vibration element placed against the forehead. To test the device, she stood outside an ear clinic, asking those entering and leaving the building to try on her hearing helmet. Some said that it worked better than the standard hearing aids they normally used.

Bike breath

Normally powered by electricity, nebulizers spray medication into extremely small particles for inhalation, helping ease breathing for people with asthma. But in places where asthma is common but reliable electricity isn't, an alternative was needed. This foot-powered nebulizer uses a floor pump that normally inflates bicycle tires to spray medicated mist, helping people with asthma to inflate their lungs.

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