MicroVisk's current prototype requires blood to be applied using a pipette. But the company is about to engineer a device that captures and analyzes a sample in one go, similar to a glucose-testing kit. The company was recently granted a European patent and secured $1.7 million in funding, and its aim, says Curtis, is to come to market within three years.

Given that similar approaches have been used to measure viscosity at a macroscopic level, the approach should work well at a microscopic level too, says Todd Przybycien, head of biochemical and chemical engineering at Carnegie Mellon University, in Pittsburgh. He adds that measuring viscosity, rather than trying to detect specific particulates in blood, is a more manageable task.

In March, the Centers for Medicare and Medicaid Services (CMS) extended its health-insurance policy to allow Warfarin patients in the United States to be covered for more-frequent testing at home. "The market for testing patients on Warfarin is huge, with a global value at over $2.25 billion," Curtis says. "This is going to end up much like the glucose-testing market."

"By limiting doctor visits, MicroVisk will make life much more manageable for people taking Warfarin," says Phil Cooper, director of the Sensors and Instrumentation Knowledge Transfer Network, an academic and industry group based at the National Physical Laboratory, in Oxfordshire, U.K., which supported MicroVisk in its early stages.

Other devices that perform a similar job are becoming available but are less accurate, Curtis says, because they measure coagulation through indirect biochemical changes--for example, by applying a current to the blood and measuring impedance. The other advantage of using a MEMS sensor is that it requires less blood. "We require about one microliter of blood, as opposed to between 10 and 15 microliters," Curtis adds. This means that each blood test requires a smaller pinprick. "You're going to cut through a lot less nerve endings, so it hurts less," he says.