Novel inertial impactor for nanoparticle classification without particle loading effect

Particle size classifiers are widely used to separate particles at a certain aerodynamic diameter below which particles are used for various purposes. However, it is hard for current available classifiers to achieve nanoparticle classification at high particle mass loading conditions in addition to the cost of high pressure drop. In this study, a nanoparticle inertial classifier (NIC) was developed to classify nanoparticles without particle loading effect for the long term. The NIC operated at a 3 L/min flow rate consists of a micro-orifice plate with 163 nozzles and a wetted glass fiber filter substrate through which water is injected upward to wash off deposited particles continuously. This study is the first to achieve a 100 nm cutoff aerodynamic diameter with such a low pressure drop of 8.3 kPa for inertial classification. The NIC showed good number-based and mass-based classification performance for NaCl particles with a narrow nanoparticle size distribution. The NIC also performed well for generating stable nano-TiO₂ particles with different feeding mass concentrations up to 92.18 mg/m³ during a 60-min operation. The current 3 L/min NIC thus can serve as a nanoparticle classifier with high loading mass concentration for future applications such as nanopowder classification or inhalation toxicity testing.