Determination of exposure to engineered carbon nanoparticles using a self-sensing piezoresistive silicon cantilever sensor

Abstract

A novel MEMS-based cantilever sensor with slender geometry is designed and fabricated to be implemented for determining personal exposure to carbon engineered nanoparticles (NPs). The function principle of the sensor is detecting the cumulative mass of NPs deposited on the cantilever surface as a shift in its resonant frequency. A self-sensing method with an integrated full Wheatstone bridge on the cantilever as a piezoresistive strain gauge is introduced for signal readout replacing optical sensing method. For trapping NPs to the cantilever surface, an electrostatic field is used. The calculated equivalent mass-induced resonant frequency shift due to NPs sampling is measured to be 11.78 ± 0.01 ng. The proposed sensor exhibits a mass sensitivity of 8.33 Hz/ng, a quality factor of 1,230.68 ± 78.67, and a temperature coefficient of the resonant frequency (TC f) of -28.6 ppm/°C. These results and analysis indicate that miniaturized sensors based on self-sensing piezoresistive microcantilever can offer the performance to fulfill the requirements of real-time monitoring of NPs-exposed personnel

2.4.5 Silicon Cantilever Resonators Integrated with Portable Electrostatic Samplers for Sensing and Characterizing Engineered Nanoparticles in Workplace Air

“…A mass sensitivity S = Δf / Δm = 32.75 Hz/ng and a sampling efficiency η = Δm / m NP × 100 % = 1.33 % are therefore yielded from this experiment. This sampling efficiency was improved by a factor of eleven compared to the previous result [2]. Nevertheless, these results are still very low.…”

“…The first module which is a silicon cantilever resonator (length l = 1.25 mm, width w = 26.5 μm, height h = 39.3 μm) has a full Wheatstone bridge on its clamped end as a piezoresistive element for reading the signal output of the sensor via a strain-to-resistivity change. The cantilevers are manufactured by utilizing a silicon bulk micromachining process based on photolithography, diffusion, and inductively coupled plasma (ICP) cryogenic deep reactive etching (cryo-DRIE) which offers many benefits including precise control of dimensions, integration and miniaturization of devices, and fabrication of an array of devices [2]. An external piezostack adhered to the cantilever supporting frame was used to actuate the cantilever, such that the resonator was able to operate at the first higher harmonic bending frequency f of 221.5 kHz with a quality factor Q of 1950.…”

“…Such MEMS-based resonant sensors can count the cumulative mass of particles deposited on their surfaces as a shift in their resonant frequencies with high measuring precision. From the previous work, a self-sensing silicon cantilever was investigated in an air pollution sampling of ~20 nm carbon ENPs which resulted a mass sensitivity of 8.33 Hz/ng [2]. Nevertheless, the used commercial nanometer aerosol sampler (TSI 3089) was too bulky and heavy to be implemented in a portable sensing system.…”

Performance of an Electrothermal MEMS Cantilever Resonator with Fano-Resonance Annoyance under Cigarette Smoke Exposure

“…Hence, the increase in RH at 60 and 90 min can be estimated to have a contribution of only 3.1% to 4.4% to the measured ΔfEPC under cigarette smoke exposure. Furthermore, Wasisto et.al [39] identified the temperature coefficient of the resonant frequency of a silicon cantilever of αf = 28.6 ppm/°C. Accordingly, the decreasing temperature of ΔT ~2 °C in this work (see open circle line in Figure 9), according to Δf/f0 = αf × ΔT, led to a resonance shift of ~12 Hz.…”

Fabrication of Holder-type Piezoresistive Cantilever for Embryo Mass Measurement

“…On the other hand, a cantilever-based sensor for physical, chemical, and biological analysis has been reported. (12)(13)(14) The mass of carbon, metal, and metal oxide nanoparticles was detected using silicon resonant cantilever-based mass sensors (15,16) or silicon nanopillar resonators with sub-femtogram mass resolution. (17,18) We have also developed a self-sensing high-sensitivity sensor using a piezoresistive cantilever, (19) and have succeeded in antibody-antigen reaction measurement with the mass sensitivity of 190 fg/Hz.…”