Method and apparatus for sample injection in microfabricated devices

Abstract

An off-column sample injection scheme for introducing samples into micro-reaction channels in microfabricated devices. In one aspect of the present invention, off-column sample injection is effected by introducing sample from a sample reservoir provided on the substrate of the microfabricated device into a reaction channel via a constricted channel or opening interface, e.g., a narrow connection-channel and / or a pinhole. In another embodiment of the present invention, off-column sample injection is effected by introducing sample from a sample reservoir that is provided outside the substrate of the microfabricated device. A through-hole is provided in the substrate to facilitate sample introduction into the reaction channel. In a further aspect of the present invention, the free-end of a capillary tube connected to the sample-channel is moved alternatively to a sample and an auxiliary solution to bring multiple samples in series to the vicinity of a reaction channel for convenient sample introduction and high-throughput assays.

Description

[0001] This patent application claims the benefit under 35 U.S.C. .sctn. 119(e) of U.S. Provisional Patent Application Serial No. 60 / 267,474, filed on Feb. 9, 2001.[0002] 1. Cross-Reference[0003] U.S. patent application No. ______entitled METHOD AND APPARATUS FOR REPRODUCIBLE SAMPLE INJECTION ON MICROFABRICATED DEVICES, concurrently filed on Feb. 11, 2002 (Attorney Docket No.: 1093 / 202), which is assigned to MicroChem Solutions, Inc., the assignee of the present invention, and which is fully incorporated by reference herein.[0004] 2. Field of the Invention[0005] The present invention relates generally to miniature instrumentation for conducting chemical reaction and / or bio-separation, and diagnostics and / or analysis related thereto, and more particularly, to the introduction of samples to the chemical reaction and / or bio-separation channels in microfabricated devices.[0006] 3. Description of Related Art[0007] Bioanalysis, such as DNA analysis, is rapidly making the transition from a...

AI Technical Summary

Problems solved by technology

Yet due to the complexity of the equipment that detects and measures DNA samples and the difficulty in preparing the samples, the existing DNA analysis procedures are often time-consuming and expensive.

Capillary electrophoresis techniques are employed in seemingly limitless applications in both industry and academia.

The limitation of this method is the large sampling volume.

This volume is too large to be used for high-resolution separations.

Later, an internal loop injection valve with an injection loop volume of .gtoreq.20 nL has become commercially available, but connecting capillaries to this valve is too much of a challenge and consequently it is not often used in capillary electrophoresis.

It is also difficult to maintain consistency in injecting a fixed volume of sample by either of these techniques, as the sample volume injected are susceptible to changes in sample viscosity, temperature, etc., thereby resulting in relatively poor reproducibility in injected sample volumes between separation runs.

Electromigration additionally suffers from electrophoretic mobility-based bias.

Often, the readlength of DNA sequencing is limited by the low signal intensity rather than the resolution for the long fragments.

This degrades the resolving power and makes the separation irreproducible.

Double-T injectors also suffer from dispersion of analytes into the separation channel.

However, when samples of different ionic strength and viscosity are to be analyzed, that calibrated potential balance for the device is no longer applicable, and consequently giving rise to undesired and / or irreproducible results.

On the other hand, a considerable increase in the steady-state concentration will occur at the sample / gel interface for the large fragments because of their reduced mobility in the gel.

However, there are two major problems associated with the T-injector.

The first problem is the augmented electrophoretic mobility-based bias.

The second problem is the difficulty in precisely controlling a finite amount of analytes into the separation-channel 6.

This problem is associated with the variation of length of the half "cross-channel" 8.

The reservoirs are holes drilled or physically attached and their positions and dimensions cannot be reproducibly and precisely produced.

Because analytes going to the separation-channel have to pass through the half "cross-channel" 8, it is a significant challenge to attempt to control the timing so that only a given finite amount of analytes is allowed to migrate into the separation-channel 6.

Variation of the length of this channel makes the problem even more challenging.

In addition, prior art systems had not adequately addressed the issues and challenges relating to interfacing microfluidic channels with real-world sample and reagent solutions before the full benefits of microfluidic systems can be realized.

Images