Microscope stage, Temperature stage & Cooling stage for microscopy imaging
Regarding temperature stage, biological processes are very sensitive, and respond rapidly to temperature variation. Microscope stage, cooling stage, hot stage are one way to control or shift the temperature of a sample. 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.
Introduction
Microscope thermal stages can thermalize across a large range of temperatures, from -190°C to more than 500°C depending on the application. This is why they are the system of choice for applications where very high freezing/heating rates are required. However, simpler microscope stages exist for live cell imaging purposes in biological research, with temperature ranges between -5° C and 99°.
How does a microscope stage heater work?
Heater/cooler microscope stages can be used in most of upright and inverted microscopes. They have a very high thermal capacity and use resistive heaters (hot stage) or Peltier devices to heat or cool down (cooling stage only when Peltier modules are used). They are based on two principles: conduction and diffusion. The metal of the device is in contact with the glass slide of the sample and a thermal bridge (conduction) is generated between the system frame and the slide. The heat then moves by diffusion inside the slide (diffusion) until it reaches the sample. It reduces the formation of thermal gradient on the sample.
Features
Large thermalization range
Heating/cooling temperature stages can thermalize in big ranges. Systems based on Peltier elements can easily go below room temperature. This is an important features, notably for scientists studying microtubules assembly or vesicular transport.
Relatively fast temperature shifts
The power and the efficiency of the heating/cooling microscope stages make these systems much faster in operating temperature shifts when compared to incubation boxes. Depending on the type and power of the temperature actuators, temperature shifts can be achieved within 2 to 3 minutes. Nevertheless these systems are often prone to temperature overshoots when fast and large temperature shifts are applied.
Flexibility in specimens and easy access to the cells
Thermal stage adaptors are compatible with different types of specimen (microscope slide, Petri dishes, etc…). Operators can have a direct access to the cells during the experiment.
Drawbacks
Poor temperature uniformity across the sample
Microscope stages ultimately thermalize the sample by thermal diffusion. The distance between the heating source and the sample can generate significant thermal gradients across the sample.
Requires objective heating to achieve accuracy
When working with water or oil immersion objectives, hot stages & cooling stage should be coupled with objective collars to mitigate the heat sink established by the thermal bridge created between the sample and the objective by the oil/water. Indeed, when the objective, the oil, and coverslip make contact, the objective acts as a heat sink leading to up to 5-7°C discrepancy in sample temperature.
Requires dehumidifier
While microscope stages allow to reach temperature below ambient, it is recommend to use a room dehumidifier to prevent a strong condensation of water close to the sample and the microscope elements.
Ergonomy
These systems are custom-installed on specific stages and cannot be moved from scopes to scopes.
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