Tiny Turbine Inside Arteries Could Power Pacemakers—and Cause Blood Clots

Fascinating stuff.
http://blogs.discovermagazine.com/80beats/2011/05/17/tiny-turbine-inside-arteries-could-power-pacemakers-and-cause-blood-clots/
The URL contains a picture if you want to see one.
What’s the News: Tiny turbines that fit inside human arteries could produce enough energy to power pacemakers and other implantable devices, according to preliminary tests by Swiss researchers presented at a conference earlier this month. The turbine would essentially serve as a tiny generator, gathering power from blood rushing by after it’s been pumped by the heart. This power source could be a boon for medical devices that currently require batteries or cables for power. Unfortunately, the turbulence these turbines create would likely cause blood clots, which could lead to heart attack or stroke—an extremely dangerous side effect that makes having to replace a battery not seem so bad.
How the Heck:
The idea is to harvest a part of the energy the heart is already putting out. “The heart produces around 1 or 1.5 watts of hydraulic power,” mechanical engineer Alois Pfenniger, one of the researchers, told IEEE Spectrum. “A pacemaker only needs around 10 microwatts.”The researchers tested three pre-made mini-turbines in a thin tube about the size of the internal thoracic artery, which doctors often use in coronary bypasses and other surgeries.
The most efficient turbine they tested produced about 800 microwatts, or 80 times what an average pacemaker needs to run.
Uh Oh:
As the turbines spin, they create turbulence. This can cause blood to coagulate, which could trigger potentially life-threatening blood clots. If these turbines are going to power medical devices, the benefits (not having to change a battery or connect a cable to another power source) have to outweigh the risks (dangerous blood clots). This side effect is a serious hurdle to any clinical use.
The researchers may come up with a new design or improve on an entirely new one to cut down on turbulence, running computer simulations to test out different models.
Once the turbulence issue is addressed, there may be other challenges to putting turbines into real arteries, including long-term stability and reliability.
What’s the Context:
If they make it to the clinic, these turbines could be used to power pacemakers, drug delivery pumps, electrodes, and medical monitoring devices.
Other researcher groups are testing out different ways to glean power from the circulatory system, with mixed results. One approach gets energy from changes in blood pressure generated by the heartbeat, but doesn’t yet produce enough power to run a pacemaker;  another converts mechanical to electrical energy with a transducer placed next to a moving organ.