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With support by this PRF-G grant during the past year, we have accomplished several key steps towards the research plan that was originally proposed. The impact of the progress on our overall research program is significant. Student education is also a valuable component of the activities made possible by this grant. In particular, one graduate student received intensive training in the field of optically-detected magnetic resonance imaging (MRI) in the summer period. Finally in this report, I would like to lay out the remaining steps in order to use our best effort to finish the proposed research plan in time. Details are described in the following sections:

ACCOMPLISHMENTS

The most important and challenging step for optically-detected MRI is to detect nuclear magnetization. Using a compact optical atomic magnetometer, we successfully detected nuclear magnetization of 100-microliter water, with a signal-to-noise ratio of nearly 40 using 30-ms integration time. The magnetometer operates at 34-37 degree Celsius, much lower than that of similar apparatus in literature. It allows convenient coupling of sample with the magnetometer without thermal insulation. The compact design of the instrument and small size of the atomic sensors substantially improve the detection limit of analyte because of the fact magnetic field is inversely proportional to the cubic of the distance between the analyte and the detector. We also reveal the stability and sensitivity of the apparatus are not significantly affected by the absence of a laser stabilization device. This is an important characteristic for applications of our technique, especially for petroleum-related applications. A related manuscript has been submitted to Optics Letters.

For flow imaging with optically-detected MRI, the stability of the flow setup is crucial. Using a computerized Micropump, we successfully established a recycled-flow mode that brings only negligible noise to the measurements. As a consequence, high-pressure gas is no longer needed to drive the analyte through the sample materials. More importantly, the amount of analyte required is dramatically reduced. For example, the overall volume of analyte is less than 10 ml using our new flow design, compared to tens of liters in related previous publications. It is now feasible to study analytes other than water in porous materials, which was previously not possible because of the availability and cost.

One of the most significant advantages of optically-detected MRI is its low-field capability. The audio frequency radiation penetrates much deeper into conductive materials than radiofrequency waves associated with conventional high-field MRI. We have successfully obtained flow profiles of water inside porous steel samples in the Earth’s magnetic field. The signal amplitude varies as a function of the average pore size, indicating different degree of relaxation enhancement on the proton spins by the porous material. Scanning electron microscopy is used for complimentary characterization. A manuscript describing this study is in preparation.

IMPACT ON MY OVERALL RESEARCH

Support by this grant played a critical role in my overall research program. The capability of detecting nuclear magnetization, which has been successfully demonstrated, is a prerequisite for optically-detected MRI for flow imaging. In this sense, this grant helped pave the way for further development of this technology. Extensive applications are expected in the field of fundamental understanding of molecules residing in porous materials.

Our preliminary results supported by this grant are also imperative to building up our confidence in our research capability. It showed that we were able to make new discoveries for the first time in a junior faculty’s laboratory. This outcome is exactly the mission of the PRF-G program in my opinion.

IMPACT ON STUDENT TRAINING

As important as research development is student training. During the summer, one graduate student (female) received intensive training in related fields. Significant progress has been made, evidenced by a submitted manuscript and another one in preparation. The student is the first author on both manuscripts.

I would also like to point out broader impact on one undergraduate student. Although not supported by this grant, he worked with the graduate student during the summer and gained substantial training in science and engineering. Partially with support from our group, he was awarded a fellowship from our university.

OUTLOOK FOR NEXT YEAR

For the next and final year of this grant, we will carry out research in two related fronts. One is to keep developing techniques to facilitate study of more complex flow processes. The strategies include stopped-flow setup, and calibration of gradient coils for four dimensional imaging (three spatial dimensions and one temporal dimension). The other front is to expand the scope of the analyte and sample material. Analyte includes 19F-containing fluids and multiphase fluids; materials include various zeolites and composite materials. We believe we are on pace to finish the proposed research in time because the most critical steps have been achieved this year.