Temperature control for microscopy imaging :
heater/cooler microscope stages
Biological processes are very sensitive, and respond rapidly to temperature variation. Performing live-cell imaging implies maintaining the cell’s temperature as long as image acquisition is required. Several temperature controllers are available on the market, all have advantages and caveats, and depending on your experimental needs they may meet your requirements. Microscope stage heater/cooler is one way to control or shift the temperature of a sample.
How does a microscope stage heater work?
Microscope stages heater/cooler are a substitute to your regular stage. They have a very high thermal capacity and use resistive heaters or Peltier devices to heat or cool down the sample. Temperature controlled microscope stages change the temperature by thermal diffusion through the glass slide or metal heat conducting bridge, which reduces the formation of thermal gradient on the sample. Microscope stages temperature range from -20C to 100C and temperature-shift occurs within minutes.
Large temperature range
-20C to 100C, the use of a Peltier element allows microscope stage to reach temperature below ambient. This is an important features, notably for scientists studying microtubules assembly or vesicular transport.
Fast temperature switch
Since the surface to thermalize is limited to the microscope stages, the speed of temperature switch is much faster than for an incubation chamber. Depending on the power of the temperature actuators, the temperature switch can be achieved in 2 to 3 min, but overshoots of several °C should be expected when system speed is increased.
Easy access to the cells
Depending on the choosen setting, manipulator can have access to his cells during his experiment. Possibility to add drugs or medium without changing the objective focus or stopping the recording of the ongoing experiment.
Poor temperature uniformity across the sample
Microscope stages control sample temperature using thermal diffusion. The heat transfer from the temperature control device to the sample can generate thermal gradient up to several degree on the sample.
Requires objective heater
The use of oil or water immersion objectives will require the use of an objective heater. Indeed, when the objective, the oil, and coverslip make contact, the objective acts as a heat sink leading to 5-7C in sample temperature. Also, a strong gradient can arise if the microscope stage temperature shift response is faster or slower than with the collar system.
While microscope stages allow to reach temperature below ambient, it is recommend to use a dehumidifier to prevent condensation.
Lack of active cooling system
Since there is no active cooling system, samples are subjected to strong temperature increase when using DIC illumination or during extended observation under epi-fluorescence microscopy. There is also a heat diffusion to nearby microscope element which may affect the objective focus.
Mono temperature control
Only one temperature can be set on the microscope stage temperature controller. While other systems allow to set two temperature at once and shift from one to the other ultra-rapidly.