A temperature-controlled stage for laser scanning confocal microscopy and case studies in materials science

Abstract

If confocal microscopy is an ubiquitous tool in life science, its applications in chemistry and materials science are still, in comparison, very limited. Of particular interest in these domains is the use of confocal microscopy to investigate temperature-dependent phenomena such as self-assembly, diffusio- or thermophoresis, or crystal growth. Several hurdles must be solved to develop a temperature-controlled stage for laser scanning confocal microscopy, in particular regarding the influence of an elevated temperature gradient close to the microscope objective, which most people try very hard to avoid. Here we report the design of a temperature-controlled stage able to generate stable temperature gradients in both positive and negative temperature range and does not require use of liquid nitrogen. Our setup provides an excellent control of the temperature gradient, which can be coupled with a controlled displacement of the sample, making it useful in particular for a variety of solidification, chemistry, and interfacial problems. We illustrate the benefits of our setup with several case studies of interest in chemistry and materials science: the 3D real-time imaging of ice growth, the segregation of hard particles by growing crystals, the freezing behaviour of single emulsions, the self-shaping of oil droplets upon cooling, and the self-assembly of amphiphile molecules into helical structures. These results show how confocal microscopy coupled with a temperature-controlled stage that provides a controlled temperature gradient is a welcome addition to the toolkit of chemists and materials scientists.

Objects interacting with solidification fronts: Thermal and solute effects

“…We performed directional freezing experiments, translating the sample along a constant linear temperature gradient of 10 Kmm −1 , using the cryo-confocal stage described previously [6]. We carried out all the experiments at V sl = the temperature gradient (G).…”

Multiple Objects Interacting with a Solidification Front

“…We conducted unidirectional solidification experiments, translating the sample cell along a constant linear temperature gradient (G), using the cryo-confocal stage described in detail previously [29]. We imposed the temperature with two Peltier modules, and controlled it with high precision (< 0.01 3 Results…”

“…This reinforces the importance of investigating the role of particle size distribution, particle-particle interactions and hence, the formation of agglomerates. Progress in studying the spatial distribution, when thousands of particles interact with a solid-liquid front, has been brought about by modern advanced in situ imaging techniques, such as X-ray imaging [28], confocal microscopy [29], or the development of numerical modelling techniques, such as molecular dynamics [30,31]. Recently, Saint-Michel et al [32] proposed a mechanical model on the effects of multiple particle interactions on particle trapping by solidification fronts as depicted in Fig.1.…”

Heat flux balance description of unidirectional freezing and melting dynamics on a translational temperature gradient stage

“…In the 1980's, a similar stage was applied to study cryopreservation of biological samples and freeze casting studies [6,7,8]. Recently this setup was used for 3D imaging of ice growth [9,10], measurement of water freezing point depression [11], ice-templating of ceramics [12] and for cryopreservation of adherent cell cultures [13].…”