Fgl400

The LCP networks utilized in this study are fabricated through the photopolymerization of liquid crystalline monomers, a diacrylate, (LC mesogen, RM82; Merck) and an azobenzene chromophore, (A1, A6A; SYNTHON Chemicals GmbH), initiated by a photoinitiator (Irgacure 819, 1 mol %: Ciba). Prior to polymerization, the monomers are dissolved in dichloromethane to obtain a homogeneous mixture, and subsequently the solvent is evaporated. Polymerization is done in a glass cell, made by gluing two glass slides coated with a polyimide alignment layer (Optimer AL1051; JSR Mircro) using UV-curable glue containing 20-µm glass bead spacers. Cell filling is done at 110 °C; at this temperature the LC mixture is isotropic. The filled cell is then cooled to 95 °C, at which temperature the LC mixture is nematic. Photopolymerization is done for 15 min, using an Exfo Omnicure S2000 lamp. A cutoff filter (λ ≥ 400 nm, FGL400S; Thorlabs is used during polymerization. A thermal treatment at 120 °C for 10 min releases thermal stresses that arise from polymer shrinkage during polymerization. After polymerization, the cell is opened, and the films are peeled from the glass with razor blades and cut into strips, in which the alignment direction of the planar side is parallel to the long side of the film. The cut strips are 2 cm long and 0.5 cm wide.

Following bacterial cell culture with or without CdS, bacterial cells are centrifuged and resuspended in a fresh M9 solution to maintain the same fluorescent background. A drop of bacterial suspension was then transferred to the microscope slide and sealed with a glass coverslip and microscope nail polish (Fisher Scientific) to prevent the evaporation of buffer. The fluorescent images of bacteria with CdS were taken with a Nikon eclipse Ti2 inverted microscope with the excitation light at 488 nm. Microspectrofluorometry of bacterial culture was performed on an inverted microscope (Olympus IX71) using an UPlanFL100x/1.30 (Olympus) oil lens. A fluorescent X-Cite lamp (120PC Q, Lumen Dynamics) was used as a light source for excitation. A U-MNUA2 filter cube with BP360-370 excitation filter and DM400 dichroic, but without emission filter, was used for spectrum recording. Residual scattering of excitation wavelength has been filtered out using GG400 colored glass filter (400 nm, long-pass; FGL400S, Thorlabs) before analysis in the spectrometer. Spectra were recorded using a Fergie spectrometer and LightField software (Princeton Instruments). The spectra were corrected after measurement for detector quantum efficiency and dichroic mirror and long-pass filter transmissions using data obtained from technical specifications.

The alignment cells
were filled with the LC mixtures at 115 °C through capillary
action. The cells were then slowly cooled such that the polymerization
temperature was T_pol = 92 °C and
left at that temperature for 15 min to ensure monodomain alignment.
For simultaneous photopolymerization, the samples were then exposed
to a flood UV exposure (5 mW/cm² UVA, Oriel Instruments)
for 5 min. For sequential photopolymerization, a 400 nm longpass filter
(Thorlabs FGL400) was used in the first illumination step to exclusively
activate the free-radical initiator for 5 min. A subsequent flood
UV exposure for 5 min polymerized the oxetane LC monomers. A postcure
of 30 min at 130 °C in an oven ensured maximum conversion and
removed any polymerization-induced stresses. The cells were then opened,
and the freestanding films were removed from the glass substrates.