Method of forming a multi-layer microfluidic device

Details Method of forming a multi-layer microfluidic device Method of forming a multi-layer microfluidic device

2001-09-14

2004-11-23

Chen, Kin-Chan (Department: 1765)

Semiconductor device manufacturing: process

Chemical etching

Combined with coating step

C438S700000, C264S019000

Reexamination Certificate

active

06821898

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to microfluidic devices, and in particular, to a method of forming a multi-layer, microfluidic device using liquid phase, photo-polymerizable materials.
BACKGROUND AND SUMMARY OF THE INVENTION
As is known, microfluidic systems are being used in an increasing number of applications. However, further expansion of the uses for such microfluidic devices has been limited due to the difficulty and expense of fabrication. By way of example, Chow, U.S. Pat. No. 6,167,910 discloses a multi-layer microfluidic device and method of making the same. The microfluidic device disclosed in the Chow '910 patent includes a body structure having a plurality of substrate layers such as a bottom substrate, a middle substrate and a top substrate. The bottom substrate includes a top surface having grooves fabricated therein in any conventional manner, such as by etching or the like. Upon the mating of the top surface of the bottom substrate with the bottom surface of the middle substrate, these grooves form a channel network for the microfluidic device. Additional channel networks may be formed by the top surface of another substrate and the bottom surface of the adjacent substrate. In such manner, multi-layer channel networks may be formed within a microfluidic device. Ports may be provided in each of the substrates to interconnect the various channel networks within the microfluidic device. It is contemplated to thermally bond the substrates together in order to form an integral, microfluidic device.
While the method disclosed in the Chow '910 patent is functional for its intended purpose, the method disclosed therein has significant limitations. By way of example, each of the substrates must be preformed using traditional microfabrication methods that involve etching. These traditional methods are inherently expensive due to the equipment, materials and process complexity issues required. Further, the cost of thermally bonding the substrates together in high temperature annealing ovens increases the overall cost to manufacture the microfluidic device. As such, it is highly desirable to provide a simpler and more economical method of fabricating microfluidic devices.
Therefore, it is a primary object and feature of the present invention to provide a method of fabricating a multi-layer, microfluidic device which is simple and inexpensive.
It is a further object and feature of the present invention to provide a method of fabricating a multi-layer, microfluidic device which has a smaller footprint than prior devices now available.
It is a still further object and feature of the present invention to provide a method of fabricating a multi-layer, microfluidic device which may be customized to a particular application without undue additional expense.
In accordance with the present invention, a method is provided for forming a microfluidic device on a base having an upper surface. The method includes the steps of providing a first layer having upper and lower surfaces and being in a space relationship to the upper surface of the base. The lower surface of the first layer and the upper surface of the base define a construction cavity therebetween. The first layer has a passageway therethrough which communicates with the construction cavity. A mask is positioned between the construction cavity and the source. The mask corresponds to a channel to be formed in the construction cavity. The construction cavity is filled with a material and a portion of the material is polymerized within the construction cavity outside of the channel with the source such that the portion of the material is solidified. The material within the channel is flushed therefrom.
The first layer may include a fill hole therethrough for allowing for the filling of the construction cavity. In addition, the passageway communicates with the channel. The passageway may be plugged to prevent material from flowing therein during filling. It is contemplated to provide a gasket about the construction cavity to maintain the material therein during filling. The step of positioning the mask includes the additional step of affixing the mask to the upper surface of the first layer.
A second layer may be provided having upper and lower surfaces and being in a spaced relationship to the first layer such that the lower surface of the second layer and the upper surface of the first layer define a second construction cavity therebetween. The second layer has a passageway therethrough which communicates with the second construction cavity. A second mask is positioned between a second construction cavity and the source. The second mask corresponds to a channel to be formed in the second construction cavity. The second construction cavity is filled with material. A portion of the material is polymerized within the second construction cavity outside of the channel with the source such that the portion of the material is solidified. The material is flushed from the channel in the second construction cavity.
The passageway through the second layer and the passageway through the first layer are axially aligned and communicate with each other through the channel in the second construction cavity. The passageways in the first and second layers may be plugged to prevent the material from flowing therein during the step of filling the second construction cavity with material. Thereafter, the passageways in the first and second layers are cleared after a portion of the material is polymerized within the second construction cavity such that the channel in the first construction cavity and the channel in the second construction cavity communicate through the passageway in the first layer. The passageway through the second layer communicates with the upper surface of the second layer through an opening. The method of the present invention may include the additional steps of covering the opening and removing the mask between the construction cavity and the source prior to providing the second layer.
It is contemplated that the passageway in the first layer communicate with the channel in the construction cavity and with the channel in the second construction cavity. The first layer includes a second passageway therethrough that communicates with the channel in the construction cavity. The passageway in the second layer communicates with the channel in the second construction cavity and with the upper surface of the second layer through a first opening. The second layer includes a second passageway therethrough that communicates with the second passageway through the first layer and with the upper surface of the second layer through a second opening. One of the openings in the second layer comprises an input and the other of the openings comprises an output to the microfluidic device.
In accordance with the still further aspect of the present invention, a method is provided for forming a microfluidic device on a base having an upper surface. The method includes the steps of providing a first layer having upper and lower surfaces and being in space relationship to the upper surface of the base. The lower surface of the first layer and the upper surface of the base to define a construction cavity therebetween. The construction cavity is filled with a material and a portion of the material is polymerized within the construction cavity so as to solidify the same. The solidified material defines a first channel. The non-polymerized material is flushed thereafter from the channel.
In order to polymerize a portion of the material, a mask is positioned between the construction cavity and a source. The mask corresponds to the shape of the first channel formed in a construction cavity. Ultraviolet radiation is generated with the source and directed towards the mask.
It is contemplated to provide a second layer having upper and lower surfaces. The second layer is spaced from the first layer such that the lower surface of the second layer and the upper surface of the first layer define a second construction cavity the

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