By 2014, the hardware components of a DIY artificial pancreas -- a small insulin pump that attaches via thin disposable tubing to the body and a continuous sensor for glucose, or sugar, that slips just under the skin -- were available, but it was impossible to connect the two. That's where the security flaw came in. The hackers realized they could use it to override old Medtronic pumps with their own algorithm that automatically calculates insulin doses based on real-time glucose data. It closed the feedback loop. [...]
Dozens, then hundreds, and now thousands of people are experimenting with DIY artificial-pancreas systems -- none of which the Food and Drug Administration has officially approved. And they've had to track down discontinued Medtronic pumps. It can sometimes take months to find one. [...]
Even with these new options, DIY looping is still on the margins of the official health-care system: It means going overseas to buy pumps not yet approved in the United States. It means testing an experimental version with Omnipod. And in most cases in the United States, it's meant finding old, out-of-warranty Medtronic pumps. Loopers with Medtronic pumps told me they worried their decade-old devices might break, and they'd have no way to fix them.
'Looping' Created an Underground Insulin-Pump Market