Development of Interdigitated Capacitive Sensor for Real-Time Monitoring of Sub-Micron and Nanoscale Particulate Matters in Personal Sampling Device for Mining Environment

While current personal monitoring devices for mining industry are optimized for monitoring microscale particles, a higher resolution technique is required to detect sub-micron and nanoscale particulate matters (PM) due to smaller volume and mass of the particles. In this work, an interdigitated capacitive sensor is designed for monitoring sub-micron and nanoscale particle concentration in real-time for mining environment and other applicable environments. The 2 mm \times12 mm disposable sensor chip fits generic air sampling cassette housing. The re-usable readout board uses resistance-capacitance (RC) delay time constant for monitoring capacitance shift and data is recorded in real-time. The sensor showed clear response with respect to a commonly used test dust, and positive capacitance shift is observed after test. Among the collected particles, about 77 % are sub-micron and most of microparticles are agglomerates of sub-micron particles. A simulation study showed that our sensor response is in a region that is proportional to the particle volume collected on sensor. A comparison with gravimetric method showed that less than 1/1000 of collected particle mass on the sampler is responsible for sensor response due to radial distribution of particle deposition and sensor location. The sensor response is converted into a standard airborne mass particle concentration (g/ \text{m}^{3} ) to demonstrate a continuous monitoring of particle concentration. An incorporated microheater improved stable capacitive sensor reading under air flow and various humidity.