Micromachined titanium for high pressure microfluidic applications

• US 8,501,029 B2
• Filed: 10/30/2006
• Issued: 08/06/2013
• Est. Priority Date: 10/30/2006
• Status: Active Grant

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Beerling, Timothy, Yin, Hongfeng
• Primary Examiner(s): Cleveland, Michael
• Assistant Examiner(s): TADAYYON ESLAMI, TABASSOM
• Application Number:
  US11/554,537
• Publication Number:
  US 20080142479A1
• Time in Patent Office: 2,472 Days
• Field of Search: 210/635, 210/656, 210/198.2, 435/6, 216/96, 216/75, 216/74, 156/272, 420/68, 422/100, 422/99
• US Class Current: 216/96
• CPC Class Codes: B01L 3/5027 by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip B01L3/5023 takes precedence; micromixers B01F33/30; microreactors for synthesis B01J19/0093; microcapillary devices in general B81B1/00
• CPC Class Codes: B81B 2201/058 Microfluidics not provided for in B81B2201/051 - B81B2201/054
• CPC Class Codes: B81C 1/00063 Trenches
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: G01N 30/6095 Micromachined or nanomachined, e.g. micro- or nanosize

Abstract

In accordance with the invention, a method for making microfluidic structures in bulk titanium is disclosed. Specific microfluidic structures include HPLC structures.

Claims

1. A method for creating a microfluidic column in a titanium substrate, the method comprising:

depositing a hard mask layer on said titanium substrate;

masking said hard mask layer with a photoresist layer;

patterning said photoresist layer;

performing an RIE etch on said masked hard mask layer to form a hard mask patterned with a shape of said microfluidic column, the shape comprising arcuate portions along a length of the hard mask layer;

and

etching through said hard mask and into but not through said titanium substrate using a DRIE etch to form said microfluidic column comprising the arcuate portions alone a length of the microfluidic column.

2. The method of claim 1 wherein said DRIE etch is selected from the group consisting of a chlorine-based DRIE etch and a chlorine-boron trichloride mixture based DRIE etch.

3. The method of claim 1 further comprising removing said patterned hard mask using fluorine based dry etch chemistries.

4. The method of claim 1 wherein said DRIE etch comprises using an inductively coupled plasma etcher with additional radio frequency power applied to a platen.

5. The method of claim 1 wherein said microfluidic structure comprises a Dean'"'"'s switch.

6. The method of claim 1 wherein said microfluidic structure comprises a capillary column.

7. The method of claim 1 further comprising:

providing a titanium sheet; and

attaching said titanium sheet to said titanium substrate using diffusion bonding.

8. The method of claim 7 further comprising forming alignment holes through said titanium sheet.

9. The method of claim 8 wherein said forming comprises electrical discharge machining.

10. The method of claim 7 wherein said titanium sheet is acid cleaned prior to said diffusion bonding.

11. The method of claim 7 wherein said diffusion bonding is performed at a temperature greater than about 750°

C. but less than about 883°

C.

12. A method for creating an integrated high pressure liquid chromatograph (HPLC) column in a titanium substrate, the method comprising:

depositing a hard mask layer on said titanium substrate;

applying a photoresist layer onto said hard mask layer;

patterning said photoresist layer;

performing an RIE etch on said masked hard mask layer to form a hard mask patterned with a shape of said integrated HPLC column, the shape comprising arcuate portions along a length of the hard mask layer;

and

etching through said hard mask and into but not through said titanium substrate using a DRIE etch to form said HPLC column comprising the arcuate portions along a length of the HPLC column.

13. The method of claim 12 further comprising removing said patterned hard mask using fluorine based dry etch chemistries.

14. The method of claim 12 wherein said DRIE etch is selected from the group consisting of a chlorine-based DRIE etch and a chlorine-boron-trichloride mixture based DRIE etch.

15. The method of claim 12 further comprising:

spinning a first photoresist layer on said titanium substrate;

patterning said first photoresist layer; and

performing a shallow RIE etch to create a beadtrap.

16. The method of claim 12 wherein said integrated HPLC structure comprises a microfluidic structure selected from the group consisting of a separation column and an enrichment column.

17. The method of claim 12 further comprising:

providing a titanium sheet; and

attaching said titanium sheet to said titanium substrate using diffusion bonding.

18. The method of claim 17 wherein a polymer based layer is laminated on said titanium sheet to accommodate attachment of an ultraviolet cell.

19. The method of claim 17 wherein said titanium sheet is acid cleaned prior to said diffusion bonding.

20. The method of claim 17, further comprising forming alignment holes through said titanium sheet.

21. The method of claim 20 wherein said forming comprises electrical discharge machining.

22. The method of claim 12 wherein a polymer microfluidic circuit is attached to said integrated HPLC structure.