In June 1998, a project has been set up by the British Technology Transfer Node (TTN) Entice to explore the potential offered by a new imaging modality, consisting of Tomographic Analysis with Scanning Microscopy (TASM). This revolutionary approach allows researchers to image below the surface of materials to show their three-dimensional microstructure. The basic technique originates from medical imaging practices, referred to as Electrical Impedance Tomography (EIT). EIT images represent the changes in electrical conductivity occurring between various types of tissue. The new Scanning Thermal Microscopy (SThM) method goes one step further, since TASM images display the 3D spatial distribution of thermal conductivity. TASM enables industrial chemists to reveal material characteristics which are of vital importance for the modelling of polymer-based systems.
Medical imaging specialists prefer to perform EIT for long term monitoring of a patient. The image is produced through the application of extremely small electrical currents to the patient's body. Next, the resulting surface voltages are recorded. As many measurements as needed for the body region of interest are taken to reconstruct the desired medical image. In a safe and non-invasive way, physiological processes can be made visual, such as the act of breathing or the peak and mean systolic changes in the cardiac cycle. The Department of Medical Physics and Clinical Engineering at the University of Sheffield has a ten year experience with the exploitation of differences in the passive electrical properties of biological tissues. Here, the first real time and multi-frequency in-vivo images were produced, as well as the very first 3D images.
Scanning Thermal Microscopy or SThM has been based on EIT to study the micro-mechanical properties of surfaces. In this approach, the probe in a scanning probe microscope consists of a resistive heater. A modulated heat input is being executed at the surface of the material, in order to detect the thermal response. The differences in thermal diffusivity and conductivity indicate distinguishable phases in the image. This allows the researchers to conduct a Calorimetric Analysis with Scanning Microscopy (CASM) on the material. Accurate calorimetric information on submicrometer scale will open up unexpected dimensions in future chemistry research. However, a lot of High Performance Computing and Networking (HPCN) power is needed to apply the EIT method to the SThM technique, since enormous data sets are implied in the process.
This is why the TTN people are involved in the TASM initiative. The research for this project has been planned to last until November 1999. Lancaster and Sheffield University both are participating respectively as SThM expert and as 3D imaging specialist. Micro Materials, the Wrexham based supplier and manufacturer of nano-indentation instruments will provide the scanning probe microscope whereas NA Software will be responsible for the computer programming technology. Two large chemical companies are partnering in the role of end-user for this innovative type of thermal microscopy. You can find more details about the general progress and evolution at the home page of the TASM project.