A mechanical micro molecular mass sensor

Document Type : Short Communication


Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076. India.



One of the bio-sensing mechanisms is mechanical. Rather than measuring shift in resonance frequency, we adopt to measure the change in spring constant due to adsorption, as one of the fundamental sensing mechanism. This study explains  determination of spring constant of a surface functionalized micro machined micro cantilever, which resonates in a trapezoidal cavity-on Silicon wafer, with the resonating frequency of 7000 cycles per second. This thin-flimsy-oxide micro-cantilever has a typical shape, and the tip of the micro-cantilever is dip-coated with chemically and biologically active material. The change in mass, due to adsorption, is detected by measuring the change in spring constant. The Force-Distance spectroscopy is used to detect the change in spring constant. The experimental results, show that the mechanical sensing scheme used, permit this surface functionalized micro machined micro cantilever to be used as a molecular mass sensor. The mechanical spring behaviour of a micro-cantilever, a micro-mechanical device can be used to develop ultra-tech micro-mechanical system using computer interface.