Atomic force microscope chamber for in situ studies of ice

Abstract

To investigate the surface morphologies of biological systems in a controlled gaseous environment (e.g., the temperature, humidity and composition), most commercial atomic force microscopes require modification. We have designed a double-jacketed environmental chamber specifically for a Nanoscope IIIa (Digital Instruments, Santa Barbara, CA) force microscope. We use cold nitrogen and thermoelectric devices to control the temperature in the chamber; the nitrogen simultaneously serves to create an inert environment. We have also designed a temperature controlled sample stage utilizing thermoelectric devices for fine temperature regulation. A variation of this sample stage allows us to image samples in fluids at cold temperatures with an O-ringless configuration. The relative humidity within the chamber is also measured with commercially available relative humidity sensors. We investigate the surface morphology of ice Ih in its pure phase and shall extend the study to ice in the presence of biological molecules, such as antifreeze proteins. We present a detailed description of our design and our first images of polycrystalline ice and single crystals of ice grown in situ from the vapor.