Stephanie Getty, Lucy Lim, Andrej Grubisic, Adrian Southard, Jerome Ferrance, Manuel Balvin, Xiang Li, Timothy Cornish, Jamie Elsila, Larry Hess, Carl Kotecki, John Hagopian, William Brinckerhoff
A number of new instrument capabilities are currently in maturation for future in situ use on planetary science missions. Moving beyond the impressive in situ instrumentation already operating in planetary environments beyond Earth will enable the next step in scientific discovery. The approach for developing beyond current instrumentation requires a careful assessment of science-driven capability advancement. To this end, two examples of instrument technology development efforts that are leading to new and important analytical capabilities for in situ planetary science will be discussed: (1) an instrument prototype enabling the interface between liquid separation techniques and laser desorption/ionization mass spectrometry and (2) an addressable excitation source enabling miniaturized electron probe microanalysis for elemental mapping of light and heavy elements.
Recently we introduced a Sub-THz spectroscopic system for characterizing vibrational resonance features from
biological materials. This new, continuous-wave, frequency-domain spectroscopic sensor operates at room temperature
between 315 and 480 GHz with spectral resolution of at least 1 GHz and utilizes the source and detector components
from Virginia Diode, Inc. In this work we present experimental results and interpretation of spectroscopic signatures
from bacterial cells and their biological macromolecule structural components. Transmission and absorption spectra of
the bacterial protein thioredoxin, DNA and lyophilized cells of Escherichia coli (E. coli), as well as spores of Bacillus
subtillis and B. atrophaeus have been characterized. Experimental results for biomolecules are compared with absorption
spectra calculated using molecular dynamics simulation, and confirm the underlying physics for resonance spectroscopy
based on interactions between THz radiation and vibrational modes or groups of modes of atomic motions. Such
interactions result in multiple intense and narrow specific resonances in transmission/absorption spectra from nano-gram
samples with spectral line widths as small as 3 GHz. The results of this study indicate diverse relaxation dynamic
mechanisms relevant to sub-THz vibrational spectroscopy, including long-lasting processes. We demonstrate that high
sensitivity in resolved specific absorption fingerprints provides conditions for reliable detection, identification and
discrimination capability, to the level of strains of the same bacteria, and for monitoring interactions between
biomaterials and reagents in near real-time. Additionally, it creates the basis for the development of new types of
advanced biological sensors through integrating the developed system with a microfluidic platform for biomaterial
samples.
Radiation in the Terahertz frequency range interacts with vibrations in the weakest molecular couplings such as hydrogen bonding, van der Waals forces, and hydrophobic interactions. The work presented demonstrates our efforts towards the development of a microfluidic device as the sample cell for presenting liquid samples within the detection region of a novel sub-THz spectrometer. The continuous-wave, frequency-domain spectrometer, operating at room temperature between 315 and 480 GHz with spectral resolution of 0.3 GHz, already demonstrated highly intense and specific signatures from nanogram samples of dry biological molecules and whole bacterial cells. The very low absorption by water in this sample cell will allow for the use of liquid samples to present cells and molecules in their natural environment. The microfluidic device design utilizes a set of channels formed with metal sidewalls to enhance the interaction between the THz radiation and the sample, increasing the sensitivity of the system. Combined with near field effects, through use of a detection probe close to the surface of the sample cell, spatial resolution less than the diffraction limit can be achieved, further reducing the amount of sample required for analysis. This work focuses on the design, and fabrication methods, which will allow implementation of the microfluidic sample cell device within the THz spectrometer. The device will be utilized for characterization of different cell types, showing that THz interrogation of liquid samples is possible.
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