Figure 2. Egg-Counter platform.

(A) The Egg-Counter platform comprises three control systems: Fluid Control, Environmental Control, and Data Control. Fluid flow is driven by pressurizing the air in the buffer bottle to ~0.5 PSI. The buffer containing suspended bacteria is then driven through tubing with an attached vibration motor that maintains the bacterial suspension. Prior to entering the Egg-Counter chip, the fluid passes through a 5 μm filter. Egg-Counter chips are mounted on the Egg-Counter platform for environmental control. A custom acrylic platform holds a digital microscope, thermoelectric cooler (TEC), heat sink, fan, and temperature controller. The chip is mounted directly on the TEC with thermal paste to maximize thermal contact. A temperature probe mounted on the glass slide under a PDMS cover, with potential air pockets displaced by thermal paste, feeds temperature data to the temperature controller. The Temperature Controller reads the temperature from the glass surface that the animals contact and controls the TEC to maintain the setpoint temperature. Data control is performed by a fanless computer and a Temperature Monitor. The computer takes experiment parameters from the user, communicates with the Temperature Monitor (which sets the temperature on the temperature controller), and starts the experiment. The PC monitors a live feed from the digital microscope and saves all frames with detectible changes. The microcontroller maintains communication with the temperature controller and receives temperature data at 5-second intervals, ultimately transferring the temperature logs to the PC. (B) An assembled Egg-Counter platform (minus microfluidic chip and fluid tubing). (C) The Egg-Counter was designed to be scalable while minimizing the footprint. Two shelves above a counter arrangement, with the top shelf housing a single monitor (for up to 8 devices), the Data Control electronic components, and custom power supplies each capable of powering 4 devices. The middle shelf houses the Fluid Control elements. Each bottle can feed 6–8 inlets (3–4 chips) and bundling the tubing between the chips and the bottle enables a single vibration controller to service multiple lines. The bottom shelf or countertop houses the environmental control platform, which is built to maintain the electronics in an elevated position. This configuration helps to separate the pressurized fluid and the electronic components.