Fig. 2

Dimensions and designs of the 3DPFS swab heads, as well as the results of CFD simulations that were conducted to evaluate the sampling pressure required for each swab head design. A Schematic representations of the three swab head designs, 1L, 1S, and 2S, with different hole geometries. 1L has a rounded rectangular hole (4 mm by 1 mm), while 1S and 2S have a single and two small round holes (1 mm in diameter), respectively. L denotes a large hole, and S denotes a small hole. B Actual images of the 3DPFS and its three swab head designs. C CFD simulation results indicating that the required sampling pressure for each model was different, with − 11.9 kPa for 1L, − 132.5 kPa for 1S, and − 66.6 kPa for 2S