Atmospheric Pressure Cell Culture Device

Our dish sample holder comprised upper Al and lower acrylic resin portion that maintained the sample solution at atmospheric pressure between the SiN films (Fig. 1). The upper W-coated SiN film was attached to the Al holder using two-sided sticky tape (No. 7602, Teraoka Seisakusho Co., Ltd, Tokyo, Japan). The W layer on SiN film was connected to the Al holder using silver conductive ink (CW2900, ITW Chemtronics, Kennesaw, GA, USA). A hand-made Al holder (15 × 15 mm square) was attached under a 35-mm culture dish adhered with double-sided tape to a 4 × 4 mm square hole in the centre (Fig. 1a,a’). A 50-nm-thick SiN film in the 0.4 × 0.4 mm square window of a Si frame (4 × 4 mm) was fixed to the square hole in the culture dish bottom. The dish was subsequently UV sterilised for 17–18 h.
4T1E/M3 mouse breast cancer cells31 32 were cultured in the holder dish for 4–5 days as described above. Next, the Al holder containing cells and second SiN film on an acrylic plate were attached and sealed as described above (Fig. 1c,c’). The Al holder received voltage bias from four nickel–hydrogen batteries (approximately 8 V each), with a total bias voltage of approximately −32 V. The resin holder, which had high electrical resistivity, insulated the terminal underside of the holder from the metal-coated SiN film (Fig. 1d).