Research and Educational Activities of the BioNanofluidics and Microfluidics Laboratory

Research Themes

Our lab is mainly interested in (1) a microfluidic/nanofluidic device, essentially a network of micro/nanoscale fluidic components, and (2) application of microfluidic and nanofluidic device to analyze biomolecules such as proteins, peptide, RNA, and DNA, which are crucial in assessing physiological state of a human. We are also working on (3) individual microscale fluidic components including micropump, microvalve, micromixer, and microscale dialyzer, (4) novel microfabrication techniques such as micro 3D printing, laser machining, and hot embossing for plastic-based microfluidic/nanofluidic devices. Lastly, we are keen to explore (5) interesting micro/nanoscale physicochemical phenomena that are not observable in conventional macroscale fluidic systems including electrokinetics and microscale heat transfer. Ultimately, we are pursuing microanalytical systems or lab-on-a-chip (LOC) that can determine clinically and biologically essential biomolecules accurately, rapidly, and reliably - so that they can replace bulky, expensive, material-consuming, but essential analytical instruments in research or clinical laboratory.


1. Novel Plastic-based Microfabrication Techniques

1.1. High-precision Laser Machining for Plastic Microfabrication

In order to fabricate a microfluidic device using hard plastic such as PMMA (polymethyl methacrylate)or PC (polycarbonate), hot embossing has been used to replicate microfluidic features made on a master-mold. However, the master mold is usually made using cleanroom-based microfabrication techniques which is costly and slow, Using optimized CO2 laser cutting on a thin plastic sheet, sub-100 μm microfluidic features can be patterned directly from a CAD design less than 10 minutes (Published in KSPE 2017, KSPE 2018, and BioChip 2018 conferences).


1.2. Advanced PMMA Chip Bonding

The cut-through PMMA sheet has to be bonded to PMMA coverslips to yield enclosed microfluidic features. Traditionally these PMMA layers are thermally bonded using a hot-embossing machine or hot press after thoroughly cleaned. However, even small dust and debris from laser cutting can cause an unbonded area, which reduces manufacturing yield. Thus, we employ a simple yet fast and reliable tape-based bonding technique TPLMPT (tape-liner-supported plastic laser micromachining and pattern transfer). We also employ solvent-assisted bonding in conjunction with solvent-assisted polishing of rough laser-cut microfeatures (Published in KSPE 2018, BioChip 2018, and MEMS 2019) conferences).


1.3. 3D printed microfluidics

The 3D printing techniques have been revolutionizing almost all branches of the manufacturing industry in terms of speed, customizability, and scalability. The 3D Printing also poses tremendous impacts on the microfluidics field because it breaks the barrier of inherent geometrical limitation of planar microfluidic devices (2D or 2.5D) to build a 3D device enabling an unprecedented improvement of its functionality. Recently, many research groups have been working toward printing a microfluidic device using SL (stereolithography) printers with PMMA (hard, transparent hard plastic)- or PDMS (flexible transparent polymer)-like material properties.


2. Electrokinetic Separation and Detection of Biomolecules

2.1. Microfluidic Isoelectric Focusing for Protein Detection

Microfluidic IEF (isoelectric focusing), regardless of advantages over conventional capillary format, relies on a bulky and expensive optical detection system. To overcome this drawback, we opt for conductivity-based protein detection. Numerical analysis based on a model protein, green fluorescence protein (GFP), indicates that focusing of protein induces detectable conductivity change. Experimental results show that GFP peaks can be successfully detected using microfluidic IEF integrated with C4D. Our novel conductivity assay could be a viable alternative to optical methods when the size and portability of the overall detection system are critical (Published in BioChip 2015, MicroTAS 2016, MicroTAS 2018 conferences).




2.2. Denaturation-free EMSA Detection of double-stranded DNA

We reported microfluidic homogeneous electrophoretic affinity (MHEA) assay for DNA quantification using zinc finger protein (ZFP) and polyacrylamide-gel (PAG) sieving matrix. Using the MHEA assay with ZFP, a nucleic-acid-binding probe, the double-stranded (dsDNA) can be directly detected without the requirement for a time-consuming DNA hybridization process. To demonstrate the performance of our assay, seb gene (Staphylococcal enterotoxin B), an important bacterial biomarker for food poisoning is analyzed. Experimental results show that the pathogen-specific dsDNA is successfully quantified (2~500 nM) with a short separation distance (197 μm) and time (14 s) facilitated by the polyacrylamide resolving gel (published in MicroTAS 2017) conference).


3. MEMS (Micro-Electro-Mechanical-Systems) for Integrated Microfluidics

3.1. PCB-based Electrolytic Micropump

We developed an electrolytic micropump based on an electrode chip fabricated on a printed circuit board (PCB). Gold interdigitated (IDT) electrodes are patterned on a PCB to minimize ohmic loss during electrolysis. As predicted by the theory of water electrolysis, the micropump produces flow rate increasing linearly with current at a wide range (1 mA–2 A). Our micropump yields the maximum flow rate of 31.6 ml/min and maximum backpressure of 547 kPa (at 34 μml/min), significantly high compared with the previous micropumps based on various actuation mechanisms including piezoelectric actuation, electroosmosis and phase change. We anticipate the PCB-based electrolysis pump will be used in portable lab-on-a-chip devices where an integrated microscale pressure source with low power consumption and simple fabrication is crucial (published in KSME 2016, KSPE 2017, KSPE 2018, MicroTAS 2017 and MicroTAS 2018 conferences, and Sensors and Actuators A: Physical 2015).


3.2. Cavitation-microstreaming Micromixer

We advance a microfluidic mixer based on cavitation microstreaming by optimizing performance using highspeed flow visualization. Using transfer tapes and experimentally optimized laser machining, a micromixer is microfabricated and assembled with ease and accuracy. For mixing, bubbles trapped in air pockets are excited at resonance frequencies using a piezoelectric actuator. The resonance frequencies of the micromixer are found using electrical impedance spectroscopy and high-speed images generated by seeded microbeads around the vibrating bubbles in the mixing chamber (published in KSPE 2017, KSPE 2018, and BioChip 2018 conferences).




4. Study of Micro/nanoscale Physicochemical Phenomena

4.1. Microfluidic Evaporation Cooling

We developed a simple water-based evaporative cooling integrated into a microfluidic chip for temperature control and freezing of biological solution. Aqueous solutions are atomized in our device and evaporation of microdroplets under vacuum removes heat effectively. We achieve rapid cooling (−5.1 ◦C/s) and low freezing temperature (−14.1 ◦C). Using this approach, the freezing of deionized water and protein (BSA) solution was demonstrated. This simple, yet effective cooling device may improve many microfluidic applications currently relying on external power-hungry instruments for cooling and freezing (published in KSME 2014, BioChip 2014 and MicroTAS 2014 conferences, and Review of Scientific Instrument 2015).

NEWS

5/30/2022
Jin Tae Kim (김진태), a 3rd-year undergraduate student, joined the BNML. Warm welcome to him.

4/19/2022
Jayoung Koo (구자영), a 1st year part-time graduate student, joined the BNML. Warm welcome to him.

4/4/2022
Bo Seok Heo (허보석), a 3rd year undergraduate student, joined the BNML. Warm welcome to him.

3/31/2022
The BNML receives a 3-year research grant from Samsung Science and Technology Foundation.

2/23/2022
The BNML receives a 5-year intermediate-level research grant from the National Research Foundation.

1/24/2022
Heeyeon Kim (김희연), a 4th year undergraduate student, joined the BNML Warm welcome to her.

1/23/2022
BNML publishes the paper "Quantitative Determination of 3D-printing and Surface-treatment Conditions for Directprinted Microfluidic Devices" to Biochip Journal (IF 3.494).

10/25/2021
BNML publishes the paper "Zinc-finger-protein-based Microfluidic Electrophoretic Mobility Reversal Assay for Quantitative Double-stranded DNA Analysis" to Biochip Journal (IF 3.494).

10/22/2021
BNML publishes the registered international patent PROTEIN MEMORY CELL AND PROTEIN MEMORY SYSTEM" (US 11,152,082).

7/27/2021
BNML publishes the paper "Cavitation-microstreaming-based Lysis and DNA Extraction using a Laser-machined Polycarbonate Microfluidic Chip " to Sensors and Actuators A: Chemical (IF 7.460).

6/16/2021
BNML presents two posters in the Biochip 2021 Spring Conference: "Cavitation-microstreaming-based Microfluidic Lysis and DNA-extraction Device" and "Quantitative Determination of 3D-printing and Surface-treatment Conditions for Direct-printed Microfluidic Devices."

5/31/2021
Haseul Lee (이하슬), a 3rd year undergraduate student, joined the BNML Warm welcome to her.

5/27/2021
The BNML receives a 1-year basic research fund from the National Research Foundation for the project titled "Acoustic microstreaming micromixer based on ultra-thin elastomeric membrane oscillator"

3/30/2021
The paper "­­Excitation-frequency determination based on electromechanical impedance spectroscopy for a Laser-microfabricated cavitation microstreaming micromixer" is just accepted to the journal Sensors and Actuators A: Physical (IF 2.904). The research was funded by Ministry of SMEs and Startups.

3/18/2021
An academiy-industry project based on our microfluidic technology is supported by the Mobile Division of Samsung Electronics.

3/3/2021
The paper "Inertial Microfluidics Enabling Clinical Research" is publihsed in the journal Micromachines (IF 2.523).This is an outcome of collaborated efforts with Hur Lab from Johns Hopkins University, USA.

2/6/2021
Jeonghwan Youn (윤전환), a 4th year undergraduate student, joined the BNML. Warm welcome to him.

1/10/2021
A master's student Hyunjin and an undergraduate student Hyeonkyu at the BNML finally graduated! Wish a great endeavor for them.