Fig. 2.

Meltblown PP filter charging design and working principle a) Schematic illustration of meltblown PP filter and PTFE film as contact layers in sliding mode case Ⅰ and case Ⅱ. b) Schematic diagrams that illustrate the process of capturing charged meltblown PP filter case Ⅰ and case Ⅱ. c) The short-circuit current of case Ⅱ. d) The open-circuit voltage of case Ⅱ. e) The surface potential of the filter front side and rear side. Error bar represents the standard deviation of ten replicate measurements. f) The filtration efficiency of the case Ⅰ and case Ⅱ of meltblown PP filter for PM_0.3–PM_10.0.