Image-charge detection is an analytical technique in which a highly-charged particle is detected by the magnitude of the image current that it generates in a detecting electrode. This current is represented as a voltage between the charged particle and the sensing electrode. It is a single particle detection method, ideal for the analysis of large, variable mass particles such as biological cells. Some of the physical properties of Bacillus subtilis spores were explored using different applications of image-charge detection. B. subtilis is a gram-negative spore-forming bacteria that has been shown to exhibit extremophile behavior. The particular extremophile behavior that was investigated in this study is the resistance to extreme mechanical stress. The effects of high-velocity impacts upon these spores were studied using image-charge detection. The elastic properties of these spores as well as spore survivability to high-velocity impacts were investigated. Spores were shown to survive impacts at velocities up to 299 ± 28 m/s. The average kinetic energy loss experienced by impacting spores, regardless of velocity at impact, was between 71 and 72%. Both conventional and novel image-charge detection techniques were used for these studies. The novel version of a charge detector that was demonstrated was fabricated using patterned metal electrodes on printed circuit boards. The simplicity and versatility of this method was demonstrated with a multi-stage charge detector, a unique bouncing detector, and charge-detection mass spectrometry detector which is capable of measuring the absolute mass of a single highly-charged particle.



College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry



Date Submitted


Document Type





bacteria, charge detection, spores, planetary protection, high-velocity impact, mass spectrometry