Strategy toward Miniaturized, Self-out-Readable Resonant Cantilever and Integrated Electrostatic Microchannel Separator for Highly Sensitive Airborne Nanoparticle Detection

In this paper, a self-out-readable, miniaturized cantilever resonator for highly sensitive airborne nanoparticle (NP) detection is presented. The cantilever, which is operated in the fundamental in-plane resonance mode, is used as a microbalance with femtogram resolution. To maximize sensitivity and read-out signal amplitude of the piezo-resistive Wheatstone half bridge, the geometric parameters of the sensor design are optimized by finite element modelling (FEM). The electrical read-out of the cantilever movement is realized by piezo-resistive struts at the sides of the cantilever resonator that enable real-time tracking using a phase-locked loop (PLL) circuit. Cantilevers with minimum resonator mass of 1.72 ng and resonance frequency of ~440 kHz were fabricated, providing a theoretical sensitivity of 7.8 fg/Hz. In addition, for electrostatic NP collection, the cantilever has a negative-biased electrode located at its free end. Moreover, the counter-electrode surrounding the cantilever and a µ-channel, guiding the particle-laden air flow towards the cantilever, are integrated with the sensor chip. µ-channels and varying sampling voltages will also be used to accomplish particle separation for size-selective NP detection. To sum up, the presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, micro-/nanoelectromechanical systems (M/NEMS)-based NP monitoring devices.

MEMS-based condensation particle growth chip for optically measuring the airborne nanoparticle concentration

We present a low-cost and compact airborne nanoparticle sensor that can count individual nanoparticles in real-time.

Design of Miniaturized, Self-Out-Readable Cantilever Resonator for Highly Sensitive Airborne Nanoparticle Detection

In this paper, a self-out-readable, miniaturized cantilever resonator for highly sensitiveairborne nanoparticle (NP) detection is presented. The cantilever, which is operated in thefundamental in-plane resonance mode, is used as a microbalance with femtogram resolution. Toachieve a maximum measurement signal of the piezo resistive Wheatstone half-bridge, thegeometric parameters of the sensor design were optimized by finite element modelling (FEM).Struts at the sides of the cantilever resonator act as piezo resistors and enable an electrical read-outof the phase information of the cantilever movement whereby they do not contribute to theresonators rest mass. For the optimized design, a resonator mass of 0.93 ng, a resonance frequencyof ~440 kHz, and thus a theoretical sensitivity of 4.23 fg/Hz can be achieved. A μ-channel guiding aparticle-laden air flow towards the cantilever is integrated into the sensor chip. Electrically chargedNPs will be collected by an electrostatic field between the cantilever and a counter-electrode at theedges of the μ-channel. Such μ-channels will also be used to accomplish particle separation for sizeselectiveNP detection. Throughout, the presented airborne NP sensor is expected to demonstratesignificant improvements in the field of handheld, MEMS-based NP monitoring devices.

Electrospun cellulose acetate nanofibers for airborne nanoparticle filtration

Reported in this paper are the effects of tip-to-collector distance, voltage, deposition time and solution concentration on the fiber size distribution and filter quality factor of electrospun cellulose acetate (CA)-based nanofibers. Nanofibrous filter samples were produced by electrospinning in a laboratory setting. The CA solutions were prepared by diluting various concentrations of CA in a 2:1 (w:w) ratio of N,N-dimethylacetamide (concentration 10–20 wt.%). The electrospinning voltages ranged from 8–12 kV, with distances from 10–15 cm and deposition times of up to 30 minutes. The produced nanofibrous filter samples were then analyzed in terms of fiber size distribution and filter quality factor using nanosized sodium chloride particles ranging from 4–240 nm in diameter. The maximum filtration efficiency measured was 99.8% for filter samples obtained with an overall deposition time of 30 minutes. The maximum filter quality factor was 0.14 Pa−1 for a CA concentration of 20 wt.% and a tip-to-collector distance of 15 cm. The average fiber diameters of the fibers were between 175 and 890 nm, and CA concentrations below 15% led to the formation of beads.

Modeling airborne nanoparticle filtration through a complete structure of non-woven material used in protective apparel

Airborne nanoparticles represent a new danger in occupational health. Numerous theoretical and experimental studies have been conducted on the efficiency of filtering media used for respiratory protection, but few have focused on media used for skin protective equipment. Indeed, a significant proportion of airborne nanoparticles can end up on the skin, causing local effects and eventually penetrating the human body. Following experimental data obtained with sodium chloride nanoparticles, the authors propose an empirical model to evaluate the penetration of airborne nanoparticles through medium used in disposable coveralls. This study presents an adaptation of the conventional filtration theory used for filtering media used in respirators. The authors' model is compared with Wang et al.'s and Brochot's models and demonstrates improvements in their descriptive ability. Moreover, a domain of validity of the proposed model was determined that will enable the evaluation of the efficiency of similar protective apparel material structures against airborne nanoparticles.