Abstract

We describe a technique for surface and subsurface micromachining of glass substrates by using tightly focused femtosecond laser pulses at a wavelength of 1660 nm. A salient feature of pulsed laser micromachining is its ability to drill subsurface tunnels into glass substrates. To demonstrate a potential application of this micromachining technique, we fabricate simple microfluidic structures on a glass plate. The use of a cover plate that seals the device by making point-to-point contact with the flat surface of the substrate is necessary to prevent the evaporation of liquids in open channels and chambers. Methods for protecting and sealing the micromachined structures for microfluidic applications are discussed.

© 2004 Optical Society of America

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  1. K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
    [CrossRef]
  2. K. Minoshima, A. M. Kowalevicz, E. P. Ippen, J. G. Fujimoto, “Fabrication of coupled mode photonic devices in glass by nonlinear femtosecond laser materials processing,” Opt. Express 10, 645–652 (2002), http://www.opticsexpress.org .
    [CrossRef] [PubMed]
  3. C. B. Schaffer, A. Brodeur, J. F. Garcia, E. Mazur, “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,” Opt. Lett. 26, 93–95 (2001).
    [CrossRef]
  4. N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron. QE-10, 375–386 (1974).
    [CrossRef]
  5. P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
    [CrossRef]
  6. X. Liu, D. Du, G. Mourou, “Laser ablation and micro-machining with ultrashort laser pulses,” IEEE J. Quantum Electron. 33, 1706–1716 (1997).
    [CrossRef]
  7. C. B. Schaffer, A. Brodeur, E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001).
    [CrossRef]
  8. Y. Li, K. Itoh, W. Watanabe, Kazuhiro. Yamada, D. Kuroda, J. Nishii, Y. Jiang, “Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses,” Opt. Lett. 26, 1912–1914 (2001).
    [CrossRef]
  9. H. Bayley, P. S. Cremer, “Stochastic sensors inspired by biology,” Nature 413, 226–230 (2001).
    [CrossRef] [PubMed]
  10. E. Southern, K. Mir, M. Shchepinov, “Molecular interactions on microarrays,” Nat. Genet. 21, 1–5 (1999).
    [CrossRef]
  11. P. J. A. Kenis, R. F. Ismagilov, G. M. Whitesides, “Microfabrication inside capillaries using multiphase laminar flow patterning,” Science 285, 83–85 (1999).
    [CrossRef] [PubMed]
  12. J. C. McDonald, S. J. Metallo, G. M. Whitesides, “Fabrication of a configurable, single-use microfluidic device,” Anal. Chem. 73, 5645–5650 (2001).
    [CrossRef]
  13. T. Thorsen, S. J. Maerlk, S. R. Quake, “Microfluidic large-scale integration,” Science 298, 580–584 (2002).
    [CrossRef] [PubMed]
  14. C. Chen, D. Hirdes, A. Folch, “Gray-scale photolithography using microfluidic photomasks,” Proc. Natl. Acad. Sci. USA 100, 1499–1504 (2003).
    [CrossRef] [PubMed]

2003 (2)

C. Chen, D. Hirdes, A. Folch, “Gray-scale photolithography using microfluidic photomasks,” Proc. Natl. Acad. Sci. USA 100, 1499–1504 (2003).
[CrossRef] [PubMed]

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

2002 (2)

2001 (5)

C. B. Schaffer, A. Brodeur, J. F. Garcia, E. Mazur, “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,” Opt. Lett. 26, 93–95 (2001).
[CrossRef]

Y. Li, K. Itoh, W. Watanabe, Kazuhiro. Yamada, D. Kuroda, J. Nishii, Y. Jiang, “Three-dimensional hole drilling of silica glass from the rear surface with femtosecond laser pulses,” Opt. Lett. 26, 1912–1914 (2001).
[CrossRef]

C. B. Schaffer, A. Brodeur, E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001).
[CrossRef]

H. Bayley, P. S. Cremer, “Stochastic sensors inspired by biology,” Nature 413, 226–230 (2001).
[CrossRef] [PubMed]

J. C. McDonald, S. J. Metallo, G. M. Whitesides, “Fabrication of a configurable, single-use microfluidic device,” Anal. Chem. 73, 5645–5650 (2001).
[CrossRef]

1999 (2)

E. Southern, K. Mir, M. Shchepinov, “Molecular interactions on microarrays,” Nat. Genet. 21, 1–5 (1999).
[CrossRef]

P. J. A. Kenis, R. F. Ismagilov, G. M. Whitesides, “Microfabrication inside capillaries using multiphase laminar flow patterning,” Science 285, 83–85 (1999).
[CrossRef] [PubMed]

1997 (1)

X. Liu, D. Du, G. Mourou, “Laser ablation and micro-machining with ultrashort laser pulses,” IEEE J. Quantum Electron. 33, 1706–1716 (1997).
[CrossRef]

1995 (1)

P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
[CrossRef]

1974 (1)

N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron. QE-10, 375–386 (1974).
[CrossRef]

Bayley, H.

H. Bayley, P. S. Cremer, “Stochastic sensors inspired by biology,” Nature 413, 226–230 (2001).
[CrossRef] [PubMed]

Bloembergen, N.

N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron. QE-10, 375–386 (1974).
[CrossRef]

Brodeur, A.

C. B. Schaffer, A. Brodeur, E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001).
[CrossRef]

C. B. Schaffer, A. Brodeur, J. F. Garcia, E. Mazur, “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,” Opt. Lett. 26, 93–95 (2001).
[CrossRef]

Chen, C.

C. Chen, D. Hirdes, A. Folch, “Gray-scale photolithography using microfluidic photomasks,” Proc. Natl. Acad. Sci. USA 100, 1499–1504 (2003).
[CrossRef] [PubMed]

Cremer, P. S.

H. Bayley, P. S. Cremer, “Stochastic sensors inspired by biology,” Nature 413, 226–230 (2001).
[CrossRef] [PubMed]

Du, D.

X. Liu, D. Du, G. Mourou, “Laser ablation and micro-machining with ultrashort laser pulses,” IEEE J. Quantum Electron. 33, 1706–1716 (1997).
[CrossRef]

P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
[CrossRef]

Dutta, S. K.

P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
[CrossRef]

Folch, A.

C. Chen, D. Hirdes, A. Folch, “Gray-scale photolithography using microfluidic photomasks,” Proc. Natl. Acad. Sci. USA 100, 1499–1504 (2003).
[CrossRef] [PubMed]

Fujimoto, J. G.

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

K. Minoshima, A. M. Kowalevicz, E. P. Ippen, J. G. Fujimoto, “Fabrication of coupled mode photonic devices in glass by nonlinear femtosecond laser materials processing,” Opt. Express 10, 645–652 (2002), http://www.opticsexpress.org .
[CrossRef] [PubMed]

Garcia, J. F.

Hartl, I.

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

Hirdes, D.

C. Chen, D. Hirdes, A. Folch, “Gray-scale photolithography using microfluidic photomasks,” Proc. Natl. Acad. Sci. USA 100, 1499–1504 (2003).
[CrossRef] [PubMed]

Ippen, E. P.

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

K. Minoshima, A. M. Kowalevicz, E. P. Ippen, J. G. Fujimoto, “Fabrication of coupled mode photonic devices in glass by nonlinear femtosecond laser materials processing,” Opt. Express 10, 645–652 (2002), http://www.opticsexpress.org .
[CrossRef] [PubMed]

Ismagilov, R. F.

P. J. A. Kenis, R. F. Ismagilov, G. M. Whitesides, “Microfabrication inside capillaries using multiphase laminar flow patterning,” Science 285, 83–85 (1999).
[CrossRef] [PubMed]

Itoh, K.

Jiang, Y.

Kenis, P. J. A.

P. J. A. Kenis, R. F. Ismagilov, G. M. Whitesides, “Microfabrication inside capillaries using multiphase laminar flow patterning,” Science 285, 83–85 (1999).
[CrossRef] [PubMed]

Kowalevicz, A. M.

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

K. Minoshima, A. M. Kowalevicz, E. P. Ippen, J. G. Fujimoto, “Fabrication of coupled mode photonic devices in glass by nonlinear femtosecond laser materials processing,” Opt. Express 10, 645–652 (2002), http://www.opticsexpress.org .
[CrossRef] [PubMed]

Kuroda, D.

Li, Y.

Liu, X.

X. Liu, D. Du, G. Mourou, “Laser ablation and micro-machining with ultrashort laser pulses,” IEEE J. Quantum Electron. 33, 1706–1716 (1997).
[CrossRef]

Maerlk, S. J.

T. Thorsen, S. J. Maerlk, S. R. Quake, “Microfluidic large-scale integration,” Science 298, 580–584 (2002).
[CrossRef] [PubMed]

Mazur, E.

C. B. Schaffer, A. Brodeur, J. F. Garcia, E. Mazur, “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,” Opt. Lett. 26, 93–95 (2001).
[CrossRef]

C. B. Schaffer, A. Brodeur, E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001).
[CrossRef]

McDonald, J. C.

J. C. McDonald, S. J. Metallo, G. M. Whitesides, “Fabrication of a configurable, single-use microfluidic device,” Anal. Chem. 73, 5645–5650 (2001).
[CrossRef]

Metallo, S. J.

J. C. McDonald, S. J. Metallo, G. M. Whitesides, “Fabrication of a configurable, single-use microfluidic device,” Anal. Chem. 73, 5645–5650 (2001).
[CrossRef]

Minoshima, K.

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

K. Minoshima, A. M. Kowalevicz, E. P. Ippen, J. G. Fujimoto, “Fabrication of coupled mode photonic devices in glass by nonlinear femtosecond laser materials processing,” Opt. Express 10, 645–652 (2002), http://www.opticsexpress.org .
[CrossRef] [PubMed]

Mir, K.

E. Southern, K. Mir, M. Shchepinov, “Molecular interactions on microarrays,” Nat. Genet. 21, 1–5 (1999).
[CrossRef]

Mourou, G.

X. Liu, D. Du, G. Mourou, “Laser ablation and micro-machining with ultrashort laser pulses,” IEEE J. Quantum Electron. 33, 1706–1716 (1997).
[CrossRef]

Nishii, J.

Pronko, P. P.

P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
[CrossRef]

Quake, S. R.

T. Thorsen, S. J. Maerlk, S. R. Quake, “Microfluidic large-scale integration,” Science 298, 580–584 (2002).
[CrossRef] [PubMed]

Schaffer, C. B.

C. B. Schaffer, A. Brodeur, J. F. Garcia, E. Mazur, “Micromachining bulk glass by use of femtosecond laser pulses with nanojoule energy,” Opt. Lett. 26, 93–95 (2001).
[CrossRef]

C. B. Schaffer, A. Brodeur, E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001).
[CrossRef]

Shchepinov, M.

E. Southern, K. Mir, M. Shchepinov, “Molecular interactions on microarrays,” Nat. Genet. 21, 1–5 (1999).
[CrossRef]

Singh, R. K.

P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
[CrossRef]

Southern, E.

E. Southern, K. Mir, M. Shchepinov, “Molecular interactions on microarrays,” Nat. Genet. 21, 1–5 (1999).
[CrossRef]

Thorsen, T.

T. Thorsen, S. J. Maerlk, S. R. Quake, “Microfluidic large-scale integration,” Science 298, 580–584 (2002).
[CrossRef] [PubMed]

Watanabe, W.

Whitesides, G. M.

J. C. McDonald, S. J. Metallo, G. M. Whitesides, “Fabrication of a configurable, single-use microfluidic device,” Anal. Chem. 73, 5645–5650 (2001).
[CrossRef]

P. J. A. Kenis, R. F. Ismagilov, G. M. Whitesides, “Microfabrication inside capillaries using multiphase laminar flow patterning,” Science 285, 83–85 (1999).
[CrossRef] [PubMed]

Yamada, Kazuhiro.

Anal. Chem. (1)

J. C. McDonald, S. J. Metallo, G. M. Whitesides, “Fabrication of a configurable, single-use microfluidic device,” Anal. Chem. 73, 5645–5650 (2001).
[CrossRef]

IEEE J. Quantum Electron. (2)

N. Bloembergen, “Laser-induced electric breakdown in solids,” IEEE J. Quantum Electron. QE-10, 375–386 (1974).
[CrossRef]

X. Liu, D. Du, G. Mourou, “Laser ablation and micro-machining with ultrashort laser pulses,” IEEE J. Quantum Electron. 33, 1706–1716 (1997).
[CrossRef]

J. Appl. Phys. (1)

P. P. Pronko, S. K. Dutta, D. Du, R. K. Singh, “Thermophysical effects in laser processing of materials with picosecond and femtosecond pulses,” J. Appl. Phys. 78, 6233–6240 (1995).
[CrossRef]

Meas. Sci. Technol. (1)

C. B. Schaffer, A. Brodeur, E. Mazur, “Laser-induced breakdown and damage in bulk transparent materials induced by tightly focused femtosecond laser pulses,” Meas. Sci. Technol. 12, 1784–1794 (2001).
[CrossRef]

Nat. Genet. (1)

E. Southern, K. Mir, M. Shchepinov, “Molecular interactions on microarrays,” Nat. Genet. 21, 1–5 (1999).
[CrossRef]

Nature (1)

H. Bayley, P. S. Cremer, “Stochastic sensors inspired by biology,” Nature 413, 226–230 (2001).
[CrossRef] [PubMed]

Opt. Express (1)

Opt. Lett. (2)

Opt. Photon. News (1)

K. Minoshima, A. M. Kowalevicz, I. Hartl, E. P. Ippen, J. G. Fujimoto, “Photonic device fabrication with femtosecond laser oscillators,” Opt. Photon. News 14, 44–49 (2003).
[CrossRef]

Proc. Natl. Acad. Sci. USA (1)

C. Chen, D. Hirdes, A. Folch, “Gray-scale photolithography using microfluidic photomasks,” Proc. Natl. Acad. Sci. USA 100, 1499–1504 (2003).
[CrossRef] [PubMed]

Science (2)

P. J. A. Kenis, R. F. Ismagilov, G. M. Whitesides, “Microfabrication inside capillaries using multiphase laminar flow patterning,” Science 285, 83–85 (1999).
[CrossRef] [PubMed]

T. Thorsen, S. J. Maerlk, S. R. Quake, “Microfluidic large-scale integration,” Science 298, 580–584 (2002).
[CrossRef] [PubMed]

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Figures (8)

Fig. 1
Fig. 1

Diagram of the micromachining experimental setup. The femtosecond pulsed laser is focused on the glass substrate by a microscope objective. The sample, mounted on a computer-controlled xyz positioner, is moved in small steps along the x, y, and z axes. PC, personal computer.

Fig. 2
Fig. 2

Various images of micromachined channels on a glass substrate. (a) SEM image showing parallel channels written near the edge of a glass slide; the group on the right-hand side is written with a larger dose of laser pulses. The channels are ∼5-μm wide and several microns deep. (b) Close-up view of the microchannels as seen through an SEM focused on the edge of the substrate. (c) Optical micrograph obtained with top illumination; the microchannels, seen as dark bands, are ∼10-μm wide, with a center-to-center spacing of ∼30 μm. (d) Optical micrograph of the same sample as in (c) obtained with illumination from below. The channels are seen as bright stripes on a dark background.

Fig. 3
Fig. 3

Diagram showing the focusing of the laser beam through a sidewall onto the partition wall between adjacent chambers.

Fig. 4
Fig. 4

Microchambers written near the edge of a glass substrate. The three chambers are ∼190 μm × 190 μm × 90 μm. The wall between the two chambers on the right-hand side has been perforated with a small, conical hole. (a) View from the side showing slight damage to the front edge of the substrate through which the laser beam was focused to create the microhole. (b) Top view from the front side showing the ∼40-μm-diameter opening of the microhole. (c) Top view from the rear side showing the ∼15-μm diameter of the tapered hole. (d) Magnified view of the tapered end of the hole. (e) Another view of the three chambers obtained by an optical surface profiler. (f) Image of the microhole as seen through an optical microscope that looks straight at the top of the partition wall between two chambers; the tapered shape of the subsurface hole is clearly visible in this image.

Fig. 5
Fig. 5

PDMS-covered microchannels on a glass substrate. (a) The PDMS layer is on the left-hand side, covering part of a laser-machined microchannel; the wide, dark diagonal band is the vertical edge of the PDMS layer. (b) An array of microchannels is partially covered by a PDMS sheet, and a pipette tip is introduced into one of the channels. (c) Pushing the pipette tip under the PDMS sheet produces a small air bubble where the flexible tip (guided by the microchannel) enters the covered region. (d) Photomicrograph of the end zone of an array of microchannels covered with a PDMS sheet and filled with water. The small white particles floating in the channels are 2-μm-diameter microbeads. These microbeads were injected into the channels through a pipette, then guided to the end zone by means of a focused laser beam (optical tweezers).

Fig. 6
Fig. 6

A 100 μm × 100 μm × 50 μm chamber connected by nine microchannels (width, ∼10 μm; depth, ∼5 μm) to the edge of the host glass slide. The chamber and parts of the channels are covered with a PDMS sheet. The chamber is subsequently filled with water injected into one of the channels. (a) Photomicrograph of the bare section of the channels; a part of the (out-of-focus) PDMS sheet is also visible on the right-hand side. (b) Covered chamber and connecting channels as seen through the PDMS layer. The bare sections of the channels (seen on the left-hand side) are now out of focus. The picture, taken by illuminating the sample from below, shows the roughness of the channel walls and the uneven nature of the machined microchamber. (c) Same as (b), but illumination is from the top. (d) A microinjector sends water through a pipette inserted into the fourth channel from the top of the picture. The presence of liquid in a region (channel or chamber) makes it appear darker than the empty regions. The liquid has now filled the chamber and is returning through several of the remaining channels. In particular, the fourth channel from the bottom is filled all the way to the edge of the PDMS layer.

Fig. 7
Fig. 7

(a) Micromachined parallel channels on a glass substrate. (b) Same channels after being filled with photoresist, then polished flush with the glass surface to remove debris and roughness in the areas between adjacent channels. Such polished substrates are covered with a PDMS sheet to create perfect (point-to-point) contact between the two surfaces. The resist is subsequently dissolved in acetone and removed.

Fig. 8
Fig. 8

Water-filling procedure for the microchambers of Fig. 4, now covered with a 20-μm-thick PDMS sheet. (a) Two micropipettes, each ∼20 μm in diameter at their tapered ends, approach and puncture the top surface of the PDMS layer. (b) Deionized water is injected by a microinjector through one pipette while the air from the adjacent chamber escapes through the other. (c) Water is seen to flow between the chambers through the microhole in the partition wall. (d) Aside from a small trapped air bubble, the second chamber is filled with water. In time the bubble escapes through the second pipette, and both chambers become completely filled.

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