Design and Application of Variable Temperature Environmental Capsule for Scanning Electron Microscopy in Gases and Liquids at Ambient Conditions
Scanning electron microscopy (SEM) of nanoscale objects in their native conditions and at different temperatures are of critical importance in revealing details of their interactions with ambient environments. Currently available environmental capsules are equipped with thin electron transparent membranes and allow imaging the samples at atmospheric pressure. However these capsules do not provide the temperature control over the sample. Here we developed and tested a thermoelectric cooling / heating setup for available environmental capsules to allow ambient pressure in situ SEM studies over the -15 °C to 100 °C temperature range in gaseous, liquid, and frozen environments. The design of the setup also allows correlation of the SEM with optical microscopy and spectroscopy. As a demonstration of the possibilities of the developed approach, we performed real-time in situ microscopy studies of water condensation on a surface of wing scales of Morpho sulkowskyi butterfly. We have found that the initial water nucleation takes place on the top of the scale ridges. These results confirmed earlier discovery of a polarity gradient of the ridges of Morpho butterflies. Our developed thermoelectric cooling / heating setup for available SEM environmental capsules promises to impact diverse needs for in-situ nano-characterization including materials science and catalysis, micro-instrumentation and device reliability, chemistry and biology.