Originally Published MPMN
Electrically Conductive Diamond Shows Promise for In Vivo MEMS Devices
Although an electrically conductive diamond film can be used for coatings on the Jarvik heart (above), the supplier also seeks to advance MEMS-based in vivo devices.
The value of diamond is on the rise. Prized in the biomedical sector for being inert, hard, and corrosion resistant, diamond has proven to be a suitable material for a variety of device coatings. Advanced Diamond Technologies (ADT), however, believes that diamond could dazzle the device industry in an even more-significant way. To that end, ADT has developed a thin-film diamond material that is both smooth and electrically conductive—a combination that it believes could help to revolutionize some MEMS-based in vivo devices.
Building on ADT’s thin-film technology, UNCD Lightning is a nanostructured form of smooth, electrically conductive diamond. To create it, ADT added boron to the chemical vapor deposition (CVD) process, which also entails the reaction of methane and hydrogen on a diamond surface to grow diamond-bonded carbon. Grains of diamond measure about 5 nm in size. “What’s special about the chemistry that we use is so-called renucleation,” explains John Carlisle, CTO of ADT. “New crystals form continually, which makes it nanostructured. And that has a number of properties that make it superior to other forms of CVD diamond that have been around longer.”
The resulting ultrathin film can currently be used for what Carlisle refers to as ‘passive’ applications, which rely on the thin-film diamond for its biocompatibility and other inherent properties. Examples include coatings on stents and hip and knee joints. Capitalizing on the ‘active’ properties of the diamond—namely electrical conductivity—and combining them with the passive traits is where the true potential lies, however.
When a charge is applied to diamond, it does not hydrolyze water unlike such materials as platinum and gold, according to Carlisle. This working potential window is crucial, he notes, in the case of biomedical electrodes, which often must interface directly with live soft tissues in vivo. Applying thin-film diamond to an electrode could open up a plethora of possibilities. “Diamond has this wide voltage window that we can communicate information through,” Carlisle says. “So, within the ±2.5 V that we have, we can transduce information across that interface electrically. This is a very well known property for electrochemists; it’s relatively rare to think about this in a biochemical context.”
Although this aim of combining active and passive diamond properties is still in its exploratory phases, it does hold promise for future biomedical applications. Being able to communicate information across tissue or blood could enable the development of devices capable of detecting glucose levels in real time and identifying particular neurotransmitters. Carlisle speculates that farther down the road, the technology could even contribute to the creation of a diamond pancreas once a functionalized surface could remain stable in water over time.Advanced Diamond Technologies
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