Atomic force microscope chamber for in situ studies of ice

To investigate the surface morphologies of biological systems in a controll ed gaseous environment (e.g., the temperature, humidity and composition), m ost commercial atomic force microscopes require modification. We have desig ned a double-jacketed environmental chamber specifically for a Nanoscope II Ia (Digital Instruments, Santa Barbara, CA) force microscope. We use cold n itrogen and thermoelectric devices to control the temperature in the chambe r; the nitrogen simultaneously serves to create an inert environment. We ha ve also designed a temperature controlled sample stage utilizing thermoelec tric devices for fine temperature regulation. A variation of this sample st age allows us to image samples in fluids at cold temperatures with an O-rin gless configuration. The relative humidity within the chamber is also measu red with commercially available relative humidity sensors. We investigate t he surface morphology of ice Ih in its pure phase and shall extend the stud y to ice in the presence of biological molecules, such as antifreeze protei ns. 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 vapo r. (C) 2001 American Institute of Physics.