Temperature control for microscopy imaging :
objective heater collar
The challenge with live-cell imaging is to maintain the cells in a physiological-like environment. Cell temperature is one of the many parameters to control during image acquisition. There are several temperature controllers available for users to choose from, and depending on the length and type of experiments some systems will be better suited than others. Objective heater/cooler collars are used as a complement of already set-up temperature controller devices.
How does objective heater collar work?
When the immersion objective, the oil (or water) and the microscope slide come in contact, the immersion objective acts like a heat sink, decreasing the actual sample temperature of several degrees (up to 10C) thus creating a thermal gradient on the sample. Most of the temperature controllers do not pre-emptively correct the discrepancy between the pre-set sample temperature and the actual sample temperature when immersion objective is used. Thus, using an objective heater/cooler collar system is a requisite with most of the temperature controllers available on the market. Two types of temperature controlled objective collars can be found :
⇒ Electronic heater collars surrounding the objective. They are used to control the heating of the objective.
⇒ Fluidic collars composed of a metallic tubing with a circular shape fixed on the objective. In these, thermalized water flows into the collar and maintain, or change, the temperature of the immersion objective.
High temperature range
The majority of objective heater collars ensure a temperature control from ambient to 43C. To reach below ambient temperature, objective heater/cooler can be used, they are fluidic collars with liquid thermalization and a pumping system.
Enhance sample temperature homogeneity
Temperature controlled objective collars can enhance temperature uniformity across the sample when using immersion objectives with any temperature controller. They prevent thermal gradient-induced artifacts.
Mono temperature control
Only one temperature at a time can be set for the objective heater collar. While other system allow to pre-set two temperatures to rapidly shift from one to the other.
Slow temperature shift
Objective heater collars have slow temperature shift (minutes). Objective heater collars are used in complement to temperature controller devices. If temperature shift is required during the experiment, sample and objective temperature shift have to timely coincide to prevent the formation of thermal gradient on the sample.
Requires experience user
It requires strong knowhow to understand artifacts generated by temperature controlled objective collars and to make the complete system work properly, especially to do temperature switch in ongoing experiments.