NanoExpo – Nanobalance detectors for individual-related measure-ments of nanoparticle exposures
The practical assessment of exposure to nanoscale aerosols that are released from synthetic materials requires a novel measurement technology based on easy-to-operate, robust sensors that are ready for use instantly after switch-on. Since currently suitable nanoparticle detectors for continuous personal and mobile measurements of workplace exposure to synthetic nanoparticles (NP) are not available at an acceptable price of less than 500€, the realisation of this approach calls for a compromise between sensor performance and sensor price.
Within the NanoExpo joint project a cantilever nanoparticle detector “Cantor” was developed that combines a microcontroller-controlled MEMS cantilever resonance balance with an electrophoretic nanoparticle separator. Determination of nanoparticle mass concentrations by means of Cantor is much faster than by means of conventional filter sampling and weighing. An upstream membrane filter or impactor ensures that no microparticles get into the measuring cell.
After calibration using the FMPS (fast mobility particle sizer), a measurement uncertainty of less than ±15% within a measurement range of 0-50µg/m3, and a detection limit of 6.5µg/m3 are achieved for carbon nanoparticles. The sampling time per measurement point is 2.4 min. The error of measurement remains at <15% in the case of variations in environmental conditions such as temperature (ΔT<1°C), humidity (ΔrF <10 %), and pressure (Δp<1kPa). The completely integrated setup with air intake, control and read-out electronics as well as LCD display weighs less than 400g. The life of the battery during continuous operation exceeds an eight-hour working shift.
The expected price of the device is particularly attractive: Due to the fact that the MEMS-manufactured cantilever balance is the only more expensive component, whereas the remaining components are standard parts, the component costs amount to only 200€. Considerable price reductions can be achieved by manufacturing larger quantities.
In an air-conditioned measurement chamber, comprehensive Cantor tests were carried out on carbon, TiO2 and SiO2 aerosols and cigarette smoke and e-cigarette vapour were analysed in the laboratory. After testing, Cantor can be easily dismantled and regenerated. Upon further optimisation of the cantilever balance and evaluation circuitry, rapid improvement is expected for parameters with a detection limit below 1µg/m3 and a sampling time of less than 1min as well as for weight and volume of the measurement cell.
