Fig 1.
Schematic diagram of the 3D dry lift-off process.
(a) A PEGDA solution with AOB was dispensed onto the first DLO mask and cross-liked by 45 seconds of 365nm UV exposure (power). (b) Photo image of the first step. (c) Second PDMS DLO mask was attached to the first PEGDA. (d) Photo image of the second step. (e) PEGDA with NOB medium dispensed onto the second DLO mask and cross-linked. (f) Microscopic image of a micro-cube after the second step. Four square pads were located on the first layer of the PEGDA. (g) Third-layer DLO mask was attached to the second PEGDA layer. The PEGDA solution with AOB was dispensed and cross-linked. (h) Schematic diagram of the PEGDA micro-cube with localized AOB (red dots) and NOB (blue dots). (i) Microscopic image of the PEGDA micro-cube with localized AOB and NOB. (j) Fluorescent microscopic image of a PEGDA micro-cube after the second DLO process. Green fluorescent micro-beads of 1 μm diameter were localized on four small square pads by the DLO process.
Fig 2.
The number of live and dead cells in the micro-cubes.
Fluorescent images of (a) the live AOB, (b) the dead AOB, and (c) the live NOB in the PEGDA micro-cubes. The images shown here are in a 50μm x 50μm field of view. (e) Bar graphs of the average ratio of live to dead cells in the PEGDA micro-cubes after UV light exposure and suspended cells in a water solution. There were no obvious differences in the dead/live ratios of the encapsulated versus the suspended cells.
Fig 3.
(a) Comparison of ammonium removal by micro-cubes and suspended samples. The control sample did not contain any bacteria. Ammonium concentration as a function of time. It is obvious from these data that the micro-cube approach had a better nitrate production volume. (b) The ammonium removal rate per single cell for suspended and encapsulated samples. (c) The ammonium removal by different numbers of PEGDA cubes. Ammonium concentration as a function of different numbers of PEGDA cubes. (d) The ammonium removal rate per single cell for encapsulated samples with different numbers of PEGDA cubes.
Fig 4.
Ammonium removal efficiencies for 1mm x 1mm and 4mm x 4mm PEGDA structures.
(a) Ammonium concentrations as a function of time for both samples. (b) Normalized ammonium removal rates for both samples.
Fig 5.
Ammonium removal rate as a function of total cell concentration.
(a) Ammonium removal profile as a function of time for different concentrations of bacteria. (b) Ammonium removal rate per cell as a function of bacteria concentration. This graph illustrates the minimum cell concentration required to maximize the efficiency of ammonium removal. Normal solution contains total bacteria of 3.6 x 108.
Fig 6.
Nitrate production rates by suspended and encapsulated cells.
(a) Nitrate production over time by encapsulated cells, suspended cells, and blanks (no cells). (b) Nitrate production rates by encapsulated and suspended cells.