TECHNICAL FIELD

The present disclosure relates to light spectroscopy for analyzing a liquid sample, and in particular to an optical cell for performing light spectroscopy.

BACKGROUND

Microfluidic technologies manipulate small amounts of fluid within channels for resource-efficient processes. Lab-on-a-chip (LOC) systems use microfluidic platforms to miniaturize standard analysis techniques, integrating one or several laboratory functions onto one device. These devices combine as many bench top fluid analysis methods as possible to a single, small-scale, low-power chip. Reduced sample sizes enables more cost-, energy-, and reagent-efficient analyses that produce less waste.

Furthermore, these devices may be automated to reduce—or even eliminate—the needed level of human involvement in environmental sampling and analysis. With in situ analysis capabilities, conventional risks of sample contamination during transport from field to lab are removed and collected data are more reliable. Possibilities of human error are reduced, and hazardous environments or chemicals may be handled with minimal risk to human life. The generally small form factor of microfluidic systems allows them to be less environmentally invasive than other methods, and their smaller sample sizes mean that they are also less destructive. Furthermore, they have the potential to do measurements at high pressures, which has been useful for prolonged sensor deployment in ocean environments.

A microfluidic absorbance cell may utilize screwed-in or epoxy-fixed fibers to couple light to/from a flow cell for sample inspection. However, fiber-based designs tend to be less transferrable from the lab to the field, where slight mechanical shocks/vibrations can result in reduced optical coupling and sensor measurement error. Alternatively, low-cost robust optical absorbance measurements may be realized by using the chip material itself. A completely integrated absorbance cell in chips fabricated from carbon-doped (tinted) semi-transparent PMMA has been developed, however it is based on a challenging alignment and fabrication process and requires either UV-curable or time setting two-part epoxies to completely immerse the LED and photodiode to hold them in perfect alignment to the microchannel. This requires a skilled and tedious workflow during the manufacturing process of these devices, where measurements must be taken to ensure optical alignment.

Accordingly, an optical cell and methods of manufacturing thereof remain highly desirable.

SUMMARY

In accordance with one aspect of the present disclosure, an optical cell for performing light spectroscopy on a liquid sample is disclosed, comprising: an inlaid sheet comprising an opaque material inlaid within a clear material; a sensing channel having first and second ends and providing a fluidic path for the liquid sample and an optical path for probe light between the first and second ends, wherein the sensing channel crosses the clear material and the opaque material; an optical input opening coupled with the first end of the sensing channel for delivering the probe light to the sensing channel; and at least one optical detection opening coupled with the sensing channel for receiving the probe light having interacted with the liquid sample.

In some aspects, the at least one optical detection opening comprises a first optical detection opening coupled to the sensing channel proximate the first end.

In some aspects, the sensing channel has a well structure with increased fluid volume where the first optical detection opening is coupled to the sensing channel.

In some aspects, the at least one optical detection opening comprises a second optical detection opening coupled with the second end of the sensing channel.

In some aspects, the optical cell further comprises fluid inlet and outlet ports respectively coupled with the first and second ends of the sensing channel.

In some aspects, the optical cell further comprises fluid inlet and outlet channels arranged in the clear material and respectively coupled with the fluid inlet and outlet ports.

In some aspects, the fluid inlet and outlet channels are coupled to the fluid inlet and outlet ports at at least one angle of 135 degrees or less relative to the sensing channel.

In some aspects, the fluid inlet and outlet channels are coupled to the fluid inlet and outlet ports at opposing sides of the sensing channel.

In some aspects, the optical input opening and the at least one optical detection opening extend from a surface of the layer of clear material to a depth of the sensing channel.

In some aspects, the optical input opening comprises an input prism disposed in the optical input opening at the depth of the sensing channel for directing the probe light into the sensing channel.

In some aspects, an optical detection opening of the at least one optical detection opening comprises an output prism disposed in the optical detection opening at the depth of the sensing channel for directing the probe light out of the optical cell.

In some aspects, the optical input opening and the at least one optical detection opening are surrounded by the opaque material.

In some aspects, the optical cell further comprises a light guide channel extending within the inlaid sheet and coupling the optical input opening and the first end of the sensing channel.

In some aspects, the opaque material has approximately 0% light transmittance.

In some aspects, the clear material has greater than approximately 90% light transmittance.

In some aspects, one or both of the opaque material and the clear material are configured to filter selected wavelengths.

In some aspects, the sensing channel has a length between 0.1 mm and 100 mm.

In some aspects, the inlaid sheet comprises first and second inlaid sheets bonded together, the first inlaid sheet comprising a first opaque material inlaid in a recess of a first layer of clear material, and the second inlaid sheet comprising a second opaque material inlaid in a recess of a second layer of clear material; and wherein the sensing channel is provided at an interface of the first and second inlaid sheets.

In accordance with another aspect of the present disclosure, a microfluidic cell is disclosed, comprising the optical cell of any of the above aspects.

In accordance with another aspect of the present disclosure, a microfluidic cell is disclosed, comprising a plurality of optical cells of any of the above aspects.

In some aspects, the plurality of optical cells are fluidly coupled to each other such that the liquid sample flows through the plurality of optical cells in series.

In some aspects, the plurality of optical cells are optically coupled to each other via optical reflectors.

In some aspects, a total optical path length of the plurality of optical cells is up to 10 m.

In some aspects, a length of the sensing channel of at least two optical cells is different, the length of each of the sensing channels being between 0.1 mm and 100 mm.

In accordance with another aspect of the present disclosure, a method for manufacturing an optical cell in a microfluidic chip is disclosed, comprising: cutting first and second inserts of an opaque material; cutting recesses in first and second sheets of clear material for respectively receiving the first and second inserts of the opaque material; inserting the first and second inserts of opaque material into the recesses of the first and second sheets of clear material to form first and second inlaid sheets; cutting a sensing channel along a bonding surface of at least one of the first and second inlaid sheets, the sensing channel crossing the clear material and the opaque material; and bonding the first and second inlaid sheets together.

In some aspects, the method further comprises defining an optical input opening and at least one optical detection opening in the first layer of clear material, wherein the optical input opening is coupled with a first end of the sensing channel, and wherein the at least one optical detection opening is coupled with the sensing channel.

In some aspects, the method further comprises cutting a prism in the optical input opening at a depth of the sensing channel.

In some aspects, an optical detection opening of the at least one optical detection opening is coupled with a second end of the sensing channel, and the method further comprises cutting a prism in the optical detection opening at a depth of the sensing channel.

In some aspects, the first insert of the opaque material surrounds the optical input opening and the at least one optical output opening.

In some aspects, the method further comprising cutting a light guide channel extending along the bonding surface of at least one of the first and second inlaid sheets, wherein the light guide channel couples the optical input opening and the sensing channel.

In some aspects, the method further comprises cutting fluid inlet and outlet ports respectively coupled with first and second ends of the sensing channel.

In some aspects, the method further comprises cutting fluid inlet and outlet channels coupled to the fluid inlet and outlet ports.

In some aspects, the opaque material has approximately 0% light transmittance.

In some aspects, the clear material has greater than approximately 90% light transmittance.

In some aspects, one or both of the opaque material and the clear material are configured to filter selected wavelengths.

In some aspects, the sensing channel has a length between 0.1 mm and 100 mm.

In some aspects, a cross-section of the sensing channel is between 0.01 mm and 1 mm.

In some aspects, the first and second sheets of clear material are a single sheet of clear material, and wherein the first and second inlaid sheets are cut from the single sheet.

