A novel resonant cantilever sensor system for liquid-phase applications is presented. The monolithic system consists of an array of four electromagnetically actuated cantilevers with transistor-based readout, an analog feedback circuit, and a digital interface. The biochemical sensor chip with a size of 3 mm x 4.5 mm is fabricated in an industrial complementary metal oxide semiconductor (CMOS) process with subsequent CMOS-compatible micromachining. A package, which protects the electrical components and the associated circuitry against liquid exposure, allows for a stable operation of the resonant cantilevers in liquid environments. The device is operated at the fundamental cantilever resonance frequency of approximately 200 kHz in water with a frequency stability better than 3 Hz. The use of the integrated CMOS resonant cantilever system as a chemical sensor for the detection of volatile organic compounds in liquid environments is demonstrated. Low concentrations of toluene, xylenes, and ethylbenzene in deionized water have been detected by coating the cantilevers with chemically sensitive polymers. The liquid-phase detection of analyte concentrations in the single-ppm range has been achieved. Furthermore, the application of this sensor system to the label-free detection of biomarkers, such as tumor markers, is shown. By functionalizing the cantilevers with anti-prostate-specific antigen antibody (anti-PSA), the corresponding antigen (PSA) has been detected at concentration levels as low as 10 ng/mL in a sample fluid.

The characteristics of resonant cantilevers in viscous liquids are analyzed. Various rectangular cantilevers geometries are studied in pure water, glycerol and ethanol solutions of different concentrations, and the results are described in terms of the added displaced liquid mass and the liquid damping force for both, the resonance frequency and the quality factor (Q-factor). Experimental results using a set of magnetically actuated resonant cantilevers vibrating in the out-of-plane ("weak-axis bending") mode are presented and compared to theoretical calculations. The importance of the study is in the use of resonant cantilevers as biochemical sensors in liquid environments.

unrolls last and is given by imax=t/D, where t is the thickness of the spiral ribbon defined by the fabrication process and D We have developed an approach to build large-area electronics the diameter of the innermost spiral winding (Fig. 3). For from monolithic silicon integrated circuits. The method used t=2gm, and assuming a maximum allowable strain of Fax=1%, deep reactive ion etching to structure a monolithic silicon a minimum node diameter of D=200m is required. If finer substrate into a stretchable, two-dimensional, wired network lithography is used to define thinner ribbons, the silicon that can be expanded to cover large planar or curved surfaces islands can be shrunk proportionally. In Fig. 4, a typical force to realize high-performance, large-area, monolithic silicon vs. displacement calculated using finite-element simulations electronics in a cost-effective manner. This approach has ( Fig. 3) is shown. The length of the spiral ribbon can be applications in sensing, smart materials, electronic textile, adjusted depending on the desired density of silicon after RFID tag and microconcentrator solar cell manufacturing.stretching.

The vibration behavior of magnetically actuated resonant microcantilevers immersed in viscous fluids has been studied. A dependence of the resonance frequency and the quality factor (Q factor) on the fluid properties, such as density and viscosity and on the cantilever geometry is described. Various cantilever geometries are analyzed in pure water and glycerol solutions, and the results are explained in terms of the added displaced fluid mass and the fluid damping force for both the resonance frequency and the quality factor. An in-depth knowledge and understanding of such systems is necessary when analyzing resonant cantilevers as biochemical sensors in liquid environments.