An SU-8 microlens array fabricated by soft replica molding for cell counting applications

Kuo, Jimmy; Hsieh, Chia‐Chun; Yang, Sung-Yi; Lee, Gwo‐Bin

doi:10.1088/0960-1317/17/4/004

Cited by 55 publications

(36 citation statements)

References 22 publications

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“…Microlens, as a key micro optics element, has found applications in optical communication (Shimura et al 2006), integral imaging system (Arai et al 2006;MartinezCorral et al 2004), backlight illumination enhancement in OLED display system (Kwon et al 2008), and lab-on-achip systems (Kou et al 2007), etc. The most popular technique for refractive microlens fabrication is the reflow process (Nussbaum et al 1997;Roy et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Because of its liquid state before curing and very low surface energy (essential for demolding process), PDMS has quickly become the most popular material in micro and nano molding processes. PDMS molding process has also been adopted in microlens fabrication (Jeong et al 2006;Kou et al 2007). However, the reported microlens fabrication processes using PDMS are all for in-plane microlens fabrication.…”

Section: Introductionmentioning

confidence: 99%

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Fast replication of out-of-plane microlens with polydimethylsiloxane and curable polymer (NOA73)

2010

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Out-of-plane microlens, as its in-plane counterpart, is an important micro optics component that can be used in building integrated micro-optic systems for many applications. In earlier publications from our group, an ultra violet (UV) lithography based technique for out-ofplane microlens fabrication was reported. In this paper, we report a replication technology for time-efficient fabrication of out-of-plane microlens made of a curable polymer, NOA73. Microlens of cured SU-8 polymer was fabricated using a unique tilted UV lithography process, polydimethylsiloxane (PDMS) was molded using the resulting SU-8 master to form a negative mold, curable polymer NOA73 was then casted in the PDMS mold and out-ofplane microlens replica made of NOA73 was finally obtained after curing. The entire replication process took less than 5 h. Since PDMS negative mold was reusable, multiple replications of the microlens could be done with the same mold and each replication only took about 30 min. Scanning electron microscopic (SEM) images showed that NOA73 microlens replica had almost identical shape as the SU-8 master. In Comparison to the SU-8 microlens, microlens replica of UV curable polymer had slightly longer focal length and smaller numerical aperture due to the lower refractive index of NOA73. In addition, NOA73 microlens replica also had improved spectral transmission. Because of its compatibility with soft lithography technique, the reported replication process may also be used to integrate out-of-plane microlens into microopto-electro-mechanical-systems (MOEMS) and BioMEMS chips.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fast replication of out-of-plane microlens with polydimethylsiloxane and curable polymer (NOA73)

2010

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“…The cylindrical lens was used to focus the excitation light, both forward scattering light and attenuated excitation light were measured. Beside cylindrical lens, molded aspherical microlens was also used in flow cytometer (Kou et al 2007). Although improved detecting efficiency was reported, the microlens was not integrated on the chip, but used in an off-chip fashion.…”

Section: Introductionmentioning

confidence: 99%

Design, fabrication, and test of an on-chip micro flow cytometer with integrated out-of-plane microlenses

Shao

Wang

2010

Microsyst Technol

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A micro flow cytometer with an integrated three-dimensional hydro-focusing unit and out-of-plane microlenses was successfully fabricated and tested. The entire system was fabricated with SU-8 ultra-violet lithography process. In the hydro-focusing unit, sheath flows pass through a trapezoid-shaped chamber with three 30°slopes to focus the sample flow in both horizontal and vertical directions. As an essential component in the on-chip optical detection system, integrated out-of-plane microlens was embedded in the sidewall of the fluid outlet channel in the detection area. A pre-aligned optical fiber holder was fabricated on chip to fix the output optical fiber in a position aligned to the microlens. Optical simulation and analysis were also conducted using commercial software Zemax. Numerical simulation results confirmed that the use of microlens substantially improved the detection efficiency by focusing the fluorescent light from the sample cells into the output optical fiber. Preliminary cell counting experiment was performed using the fabricated micro flow cytometer system and the experimental results proved the feasibility of the integrated micro flow cytometer design.

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“…The intensity of the fluorescent signals is directly related to the power amplitude of the excitation light source so that the optical energy loss leads to significant decrease of the on-chip detection method in terms of sensitivity when compared to the large-scale instrument. To address these problems, micro-lens structure fabricated by various materials and technologies has been reported [18][19][20]. In recent years, polymer micro-lens has been widely utilized for light focusing of the excitation light source and fluorescent emission due to its good optical properties and easier fabrication process.…”

Section: Introductionmentioning

confidence: 99%

“…The micro-lens can be placed on the top of the microfluidic device [21][22][23], or inside microchannels [11,24]. Basically, micro-lens can be divided into two categories, namely fixed-focal-length [18,20] and variable-focal-length micro-lens [25,26]. These micro-lenses can be also integrated with microfluidic device for on-line optical detection.…”

Section: Introductionmentioning

confidence: 99%

Microcapillary electrophoresis chips utilizing controllable micro‐lens structures and buried optical fibers for on‐line optical detection

Hsiung

Lee

2008

Electrophoresis

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In this study, a new design of a controllable micro-lens structure capable of the enhancement of LIF detection system has been demonstrated, which can be further integrated with buried optical fibers on a micro-CE chip for sample separation and detection. Two pneumatic side-chambers were placed between a micro-CE channel and an optical fiber channel. The intervals between the side-chamber and the microchannel were used to form two surfaces of the controllable micro-lens structure. Deformations of the two surfaces can be generated after pressurized index-matching fluid was injected into the pneumatic sidechambers. The side-chambers can be deflected as a double convex lens to focus both the excitation light source and the fluorescent emission signal. The profile and the focal length of the micro-lens structure can be actively adjusted by applying different liquid pressures so that biosamples with a low concentration can be detected. Using low-cost polymeric materials such as polydimethylsiloxane, rapid and reliable fabrication techniques involving standard lithography and replication process was employed for the formation of the proposed chip device. Experimental results revealed the controllable micro-lens structure can be successfully deformed as a convex lens to focus the laser light source and the collected fluorescence signal can be enhanced accordingly. The power amplitude of excitation laser light can be enhanced by 5.4-fold. FITC dye and DNA markers were then utilized for micro-CE testing. The results indicated that the signal amplitude could be enhanced 2.5-fold when compared to the case without the activation of the micro-lens. According to the experimental results, the developed device has a great potential to be integrated with other microfluidic devices for further biomedical applications.

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An SU-8 microlens array fabricated by soft replica molding for cell counting applications

Cited by 55 publications

References 22 publications

Fast replication of out-of-plane microlens with polydimethylsiloxane and curable polymer (NOA73)

Fast replication of out-of-plane microlens with polydimethylsiloxane and curable polymer (NOA73)

Design, fabrication, and test of an on-chip micro flow cytometer with integrated out-of-plane microlenses

Microcapillary electrophoresis chips utilizing controllable micro‐lens structures and buried optical fibers for on‐line optical detection

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