Portable water quality sensor fabrication method

• US 8,057,724 B2
• Filed: 01/06/2010
• Issued: 11/15/2011
• Est. Priority Date: 02/06/2004
• Status: Expired due to Fees

• Current Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Original Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Inventors: Mehta, Anjum, Halakatti, Shekhar, Cho, Hyoung Jin
• Primary Examiner(s): Barton; Jeffrey T
• Assistant Examiner(s): BALL, JOHN C
• Application Number:
  US12/683,215
• Publication Number:
  US 20100175821A1
• Time in Patent Office: 678 Days
• Field of Search: 204/451, 204/600, 204/601, 137/814, 137/833, 264/297.2, 264/645, 422502-508
• US Class Current: 264/297.2
• CPC Class Codes: B01L 2200/025 Align devices or objects to ensure defined positions relative to each other
• CPC Class Codes: B01L 2200/027 for microfluidic devices
• CPC Class Codes: B01L 2200/028 Modular arrangements
• CPC Class Codes: B01L 2300/0645 Electrodes
• CPC Class Codes: B01L 2300/0816 Cards, e.g. flat sample carriers usually with flow in two horizontal directions
• CPC Class Codes: B01L 2300/0874 Three dimensional network
• CPC Class Codes: B01L 3/502707 characterised by the manufacture of the container or its components by shaping or joining plastic parts B29C59/00, B29C65/00; by laminating B32B37/00; manufacture of microstructural devices in general B81C
• CPC Class Codes: B01L 3/502715 characterised by interfacing components, e.g. fluidic, electrical, optical or mechanical interfaces
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 7/0061 suitable for fluid transfer from the MEMS out of the package or vice versa, e.g. transfer of liquid, gas, sound
• CPC Class Codes: G01N 33/1806 Biological oxygen demand [BOD] or chemical oxygen demand [COD]
• CPC Class Codes: Y10T 137/212 System comprising plural fluidic devices or stages
• CPC Class Codes: Y10T 137/2224 Structure of body of device

Abstract

A disposable microsensor is designed, fabricated and tested for standard BOD (Biochemical Oxygen Demand) measurements. A transparent Cyclic Olefin Copolymer (COC) substrate is used for sensor fabrication. Standard lithographic procedures in addition to techniques like screen printing and electroplating are used to fabricate the sensor. A microbial strain of Trichosporon Cutaneum is immobilized over one pair of sensor electrodes while the other is used as a reference. Depending on the respiratory activities of the microbial strain in different samples, the BOD values of the samples can be measured in terms of difference between the output signals. The sensor layer is attached to an injection-molded passive microfluidic channel on the top. Advantages of the BOD microsensor include, but are not limited to, fast BOD measurement, disposability because of its low cost, chemically inert polymer substrate, flow-through sample injection scheme and integration of on-chip optics.

Claims

1. A method for fabricating a multilayer disposable microsensor comprising the steps of:

(a) forming a one-piece microfluidic package with a first side and a second side in steps consisting of;

a-i selecting a mold cavity with an inlet for injecting a chemically inert molten polymer;

a-ii defining a micro pattern of microfluidic channels having at least one set of interconnecting ports, the set having an inlet port and an outlet port, the set including one male port and one female port on a first side of the mold cavity;

a-iii defining a plurality of inlet/outlet ports on a second side of the mold cavity that is opposite to the first side, the second side having one of a microfluidic channel and a combination of a microfluidic channel and a fluid reservoir, the first side and the second side of the one-piece microfluidic mold cavity together solely providing a one-piece, integrally formed one-piece microfluidic package;

a-iv injecting a molten polymer into the mold cavity;

a-v allowing the mold to cool;

a vi allowing the molten polymer to become a rigid substrate;

(a-vii) removing the rigid substrate with a plurality of inlet/outlet ports on the first side and a microfluidic channel and a combination of a microfluidic channel and a fluid reservoir on the second side thereby providing a one-piece, integrally formed, microfluidic package capable of permitting flow-through of a sample fluid;

(b) preparing an electrode layer on a chemically inert, rigid polymer substrate that comprises a first set of electrodes, a second set of electrodes and one set of temperature sensors;

I covering the electrode layer with a dissolved oxygen selective membrane;

(d) preparing a microbial layer that is immobilized on one set of sensor electrodes;

(e) sandwiching the microbial layer between the electrode layer and the microfluidic layer;

(f) using an adhesive material to hold the electrode layer, the microbial layer and the microfluidic layer in a secure, stacked unitary arrangement; and

(g) forming a multilayer, disposable microsensor wherein the top layer is the electrode layer with a first set of electrodes, a second set of electrodes and one set of temperature sensors, the middle layer is a microbial layer immobilized on one set of sensor electrodes and the bottom layer is the one-piece, integrally formed, microfluidic package capable of permitting flow-through of the sample fluid.

2. The method of claim 1 wherein the microfluidic channel is connected to a fluid reservoir.

3. The method of claim 1 wherein the chemically inert molten polymer of the microfluidic layer is a cyclic olefin copolymer.

4. The method of claim 1 wherein the chemically inert rigid polymer of the electrode layer is a cyclic olefin copolymer.

5. The method of claim 1 wherein the dissolved oxygen selective membrane is silicone.

6. The method of claim 1, wherein the sample fluid is selected from at least one of drinking water and waste water.

7. The method of claim 6, wherein the sample fluid is drinking water.