Results
Figure 1: Bacterial growth showing heterogeneous antibiotic susceptibility
Various antibiotic susceptibilities observed within mixed bacterial communities (and even among cells within populations of species such as Escherichia coli or Pseudomonas aeruginosa) on standard agar plates reflect heterogeneous populations derived from clinical samples. This highlights the need for compartmentalized platforms capable of resolving differential growth responses at the single-cell scale and capturing division rate, thus enabling rapid and precise antibiotic selection.
Figure 2: Microfluidic generation and light-induced degradation of microgels: (a) droplet formation, (b) violet light, (c) green light (520 nm), and (d) dark incubation
Monodisperse, biocompatible microgels with disulfide crosslinks were engineered using microfluidics for externally controlled, on-demand degradation, with eosin Y serving as a light-activated trigger. They remain stable for at least two weeks in the dark, yet exposure to a gentle green light source (520 nm, 30 mW) induces complete microgel degradation within ~20 minutes.
Figure 3: Fluorescent droplets after 10 min at 37 °C
Temperature-sensitive hydrogel beads enable the generation of 100 pL bioreactors in a multiplexed system, where droplets are indexed by distinct fluorophores. This two-step protocol allows the production of up to 16 emulsions within 2.5 minutes, followed by bacterial cultivation for antibiotic susceptibility testing (AST).
Figure 4: Microfluidic chip integrated with laser-based detection
Light scattering analysis of picoliter droplets enables quantitative assessment of the number of cells per droplet. On-chip detection was optimized to correlate defined cell numbers (e.g., 0, 25, 50, and 100 cells) with scattering signals from individual droplets at a throughput of 1.2 kHz.
Current microfluidic efforts focus on minimum inhibitory concentration (MIC) studies using Escherichia coli and different antibiotics, with the goal of significantly reducing MIC screening time from days with conventional protocols to hours using droplet-based assays.