Interuniversitair Microelektronica Centrum (IMEC) (Leuven, BE) and Hasselt University (Diepenbeek, BE) have patented a diamond enhanced thickness shear mode resonator employing a high temperature piezoelectric crystal. The device features a nanocrystalline diamond coating on a silicon dioxide (SiO2) interlayer which form a langasite shear mode resonator. The thickness shear mode resonator may advantageously be used in biosensor application and in electrochemistry applications.
In U.S. Patent 7,646,138, Professor Oliver Williams University of Hasselt (Diepenbeek, BE) Institute for Materials Research (IMO) (Materials Physics Division - Wide Band Gap Materials) describes a thickness shear mode (TSM) resonator including the nanocrystalline diamond layer. The diamond layer is preferably a high quality diamond layer with at least 90% sp3 bonding or diamond bonding. Williams also developed a manufacturing method for such a resonator.
A nanocrystalline diamond thickness shear mode resonator has a number of applications in bio-sensing as well as electrochemical microgravity and visco-elastic monitoring of molecule/diamond surface interactions. In that case an upper surface of the high quality diamond layer may be functionalized.
The use of diamond in quartz crystal microbalance (QCM) may be interesting for many biological and electrochemical applications due to its wide electrochemical window, tuneable wettability by simple stable surface terminations, low friction, extreme chemical stability and bio-inertness, according to Williams.
Significantly, the surface of diamond has been shown to be particularly stable when functionalized with bio-molecules. This fact makes diamond interesting for biosensing applications by using QCM where the detection of mass loading effects could be adversely effected by bio-molecules becoming spontaneously un-tethered from the sensor surface.
Williams says the thickness shear mode resonators are simple, cheap and robust. They are capable of detecting changes in mass as low as 0.1 nanograms/cm2 and of relatively easily detecting most bio-macromolecules. The thickness shear mode resonator is a good biosensor for liquid or gas operations, with the added benefit of the wide electrochemical window of diamond.
IMEC is Europe’s largest independent research center in nano-electronics and nano-technology.
