Biomedical or Biological Micro-Electro-Mechanical- Systems (BioMEMS) have in recent years become increasingly prevalent and have found widespread use in a wide variety of applications such as diagnostics, therapeutics and tissue engineering. This paper reviews the interdisciplinary work performed in our group in recent years to develop micro-integrated devices to characterize biological entities. We present the use of electrical and mechanically based phenomena to perform characterization and various functions needed for integrated biochips. One sub-system takes advantage of the dielectrophoretic effect to sort and concentrate bacterial cells and viruses within a micro-fluidic biochip. Another sub-system measures impedance changes produced by the metabolic activity of bacterial cells to determine their viability. A third sub-system is used to detect the mass of viruses as they bind to micro-mechanical sensors. The last sub-system described has been used to detect the charge on DNA molecules as it translocates through nanopore channels. These devices with an electronic or mechanical signal output can be very useful in producing practical systems for rapid detection and characterization of cells for a wide variety of applications in the food safety and health diagnostics industries. The paper will also briefly discuss future prospects of BioMEMS and its possible impact and on bionanotechnology.
This paper describes a surface micromachined cantilever beam based oscillator detector for biological applications. This study used a novel microfabrication technique of merged epitaxial lateral overgrowth (MELO) and chemical mechanical polishing (CMP) to fabricate thin, low stress, single-crystal silicon cantilever beams. Vibration spectra of the cantilever beams, excited by thermal and ambient noise, was measured in air using a Digital Instrument Dimension 3100 Series scanning probe microscope (SPM). The cantilever beams were calibrated by obtaining the spring constant using the added-mass method. The sensors were used to detect the presence of Listeria innocua bacteria by applying increasing concentration of bacteria suspension on the same cantilever beam and measuring the resonant frequency changes in air. Cantilever beams were also used to detect the mass of the adsorbed antibodies and used to show selective capture of bacterial cells. The results indicate that the developed biosensor is capable of rapid and ultra-sensitive detection of bacteria and promises significant potential for enhancement of microbiological research and diagnostics.