Glass bottom dish

We synthesized a layer of each IMM onto glass substrates, including a glass slip (RI = 1.5255; Matsunami Glass Ind., Ltd., Japan) and a glass bottom dish (AGC Techno Glass Co., Ltd., Japan). An MY-133-EA (MY Polymers Ltd., Israel) layer was prepared by photocuring, wherein we spin-coated the MY-133-EA solution on the glass substrates at 4000 rpm for 30 s (MS-B100; Mikasa Co., Japan), followed by photo-initiated curing by irradiation with UV light from a height of ~ 2 cm using a 365-nm lamp (LUV-16; AS ONE CO., Japan, 1820 µW/cm² at a distance of 5 cm from the source), for 1 min under a nitrogen atmosphere to generate a layer of ~ 20 μm thickness. Before biofilm culture, the coated glass bottom dish was washed with 70% ethanol and then UV-irradiated on a clean bench for 10 min. The layer thickness was measured with a digital micrometer (Shinwa Rules Co., Ltd., Japan). Poly(N-hydroxymethyl acrylamide) hydrogels were prepared by chemical gelation^{32 (link)}. A pre-gel aqueous solution consisting of 8 w/v% N-hydroxymethyl acrylamide (Tokyo Chemical Industry Co., Ltd., Japan), 0.2 w/v% N,N′-methylenebisacrylamide (Tokyo Chemical Industry Co., Ltd., Japan), 0.1 v/v% N,N,N′,N′-tetramethylethylenediamine (Tokyo Chemical Industry Co., Ltd., Japan), 0.05 w/v% ammonium peroxodisulfate (Tokyo Chemical Industry Co., Ltd., Japan), and distilled water was poured into a silicon frame of 0.5 mm-thick (SR-50; TIGERS POLYMER Co., Japan) adhered to a glass bottom dish. The frame was sealed with a coverslip and incubated at room temperature (25 °C) for gelation. Agar gels were prepared by physical gelation^{32 (link)}. The agar (0.8 w/v%, Nacalai Tesque, Inc., Japan) was dissolved in phosphate-buffered saline (PBS; Fujifilm Wako Pure Chemical Co., Japan) while heating. A droplet of agar solution (150 μL) was placed on a coverslip and covered with another coverslip, followed by cooling at room temperature for gelation to form a layer with a thickness of ~ 0.5-mm thick. One side of the coverslip was gently slid off.