Fig. 2

Microfluidic-based temperature control of the elastomer microfluidic chip. a. Schematic of an elastomer chip integrating a temperature control. b. Left: Layers used to mount the chip in a. For the perfusion layer, a white background and a blue dye were used for ease of visualization. Right: assembled chip. An orange dye (temperature control) and a blue dye (perfusion layer) were used for ease of visualization. Connecting tubings were attached to the manifold using epoxy glue. See Additional file 4C for channel dimensions. The temperature control is referred to as T °C layer. c-e. All experiments used chips as in Additional file 4B, and all temperature measurements within the cell channels were made using metal electrodes deposited on glass coverslips [13]. c. Fast temperature shifts using the temperature control system. A series of switches were triggered (without a constant flow of medium) and the theoretical sample temperature was compared to experimental measurements. The theoretical temperature was calculated based on the calibration equation (Additional file 2) as well as the measured lens and thermalization fluid temperatures. d. The temperature of the sample is robust to changes in the medium flow rate. Sample temperature was set below (top) or above (bottom) ambient, and the medium flow rate was altered. No temperature changes were measured, even at the highest flow rate (80 μL/min). e. The temperature of the sample is robust to changes in immersion lens. Sample temperature was set below (top), comparable to (middle) or above (bottom) ambient, and the lens was switched back and forth between a 63X and a 100X objective (asterisks: timings of the switches). No medium flow was applied, as it has no impact on the temperature (see d). Only transitory changes in temperature were observed, corresponding to the short periods during which the microsystem was not in contact with the objectives