The microbead packing is the critical element required in the success of onchip microfabrication of critical microfluidic components for in-situ analysis and detection of chiral amino acids. In order for microliquid chromatography to occur, there must be a stationary phase medium within the microchannel that interacts with the analytes present within flowing fluid. The stationary phase media are the microbeads packed by the process discussed in this work. The purpose of the microliquid chromatography is to provide a lightweight, low-volume, and lowpower element to separate amino acids and their chiral partners efficiently to understand better the origin of life.
In order to densely pack microbeads into the microchannels, a liquid slurry of microbeads was created. Microbeads were extracted from a commercially available high-performance liquid chromatography column. The silica beads extracted were 5 microns in diameter, and had surface coating of phenyl-hexyl. These microbeads were mixed with a 200- proof ethanol solution to create a microbead slurry with the right viscosity for packing. A microfilter is placed at the outlet via of the microchannel and the slurry is injected, then withdrawn across a filter using modified syringes. After each injection, the channel is flushed with ethanol to enhance packing. This cycle is repeated numerous times to allow for a tightly packed channel of microbeads.
Typical microbead packing occurs in the macroscale into tubes or channels by using highly pressurized systems. Moreover, these channels are typically long and straight without any turns or curves. On the other hand, this method of microbead packing is completed within a microchannel 75 micrometers in diameter. Moreover, the microbead packing is completed into a serpentine type microchannel, such that it maximizes microchannel length within a microchip. Doing so enhances the interactions of the analytes with the microbeads to separate efficiently amino acids and amino acid enantiomers.
This work was done by Manuel Balvin and Yun Zheng of Goddard Space Flight Center. GSC-16514-1
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Enabling Microliquid Chromatography by Microbead Packing of Microchannels
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Overview
The document titled "Enabling Microliquid Chromatography by Microbead Packing of Microchannels" (GSC-16514-1) from NASA's Goddard Space Flight Center outlines a novel approach to micro-liquid chromatography, focusing on the packing of microbeads within microchannels for the in-situ analysis and detection of chiral amino acids. The project, led by Principal Investigator Yun Zheng, aims to enhance the understanding of the origin of life by efficiently separating amino acids and their chiral partners.
The report begins by describing the problem addressed by the project, which is the need for effective microfabrication of microfluidic components. The key innovation involves creating a dense packing of microbeads within microchannels, which is essential for the stationary phase in chromatography. The microbeads used are silica beads, 5 microns in diameter, extracted from a high-performance liquid chromatography column and mixed with a 200 proof ethanol solution to form a slurry suitable for packing.
The technical description details the packing process, which involves injecting the microbead slurry into a microchannel equipped with a microfilter at the outlet. The slurry is withdrawn across the filter using modified syringes, and the channel is flushed with ethanol after each injection to enhance packing density. This cycle is repeated multiple times to achieve a tightly packed channel of microbeads.
A unique aspect of this innovation is the use of serpentine microchannels, which maximize the length of the microchannel within a microchip. This design enhances the interaction between the analytes and the microbeads, improving the separation efficiency of amino acids and their enantiomers compared to traditional methods that typically operate on a macro scale.
The document also discusses potential commercial applications, particularly in the medical and pharmaceutical fields, where the ability to separate biologically relevant organics at a micro-scale can lead to significant advancements. Current micro-liquid chromatography methods primarily separate macromolecules, while this new approach can target the sub-components that constitute these macromolecular systems.
In summary, the document presents a significant advancement in micro-liquid chromatography through innovative microbead packing techniques, with promising implications for scientific research and commercial applications in the analysis of chiral amino acids.
