Undergraduate Research Participation at NBL

Sol-Gel Transitional Hydrogel Microarchitectures: We developed a facile method to fabricate free-standing, 3D hydrogel microarchitectures of chemically sol-gel transitional hydrogels, which is based on the use of hydrophilic substrate and aerosol of gelling agent without molding process. Using proposed methods, we fabricated hydrogel microarchitectures of sheets, meshes, or microunits without morphological distortions on the microscale. These microarchitectures can be applied as a biofabrication unit to generate complex composites with controlled microscale structures for a variety of applications such as 3D cell culture systems, tissue morphogenesis study, and modular biofabrication of artificial tissues.

Undergraduate Student (Summer 2010):
                                           Jaejung Son (Bioengineering)

Teaching Assistant: Wonhye Lee

Related Articles:
     External link Fabrication of hydrogel free-standing microarchitectures


Optoelectrofluidic Colloidal Assembly: We present a new method, termed optoelectrofluidic colloidal assembly (OCA), for preparing 2D colloidal crystals. In this letter, the first investigation of 2D colloidal assembly due to the electrohydrodynamic mechanisms in an optoelectrofluidic device has been performed. The normalized distance among the assembled particles and the assembly rate according to the applied AC signal have been analyzed. On the basis of this OCA, the control of both the colloidal crystal pattern in a large area and the distance among the assembled particles is simply possible by controlling the projected light pattern and the applied AC signal.

Undergraduate Student (Winter 2009):
                                           Youn-Hee Park (Bioengineering)

Teaching Assistant: Hyundoo Hwang

Related Articles:
     External link Optoelectrofluidic control of colloidal assembly

Microfluidic Pycnometer: A particle situated in a microfluidic interface with different fluid density moves toward the lower-density fluid, driven by the asymmetric hydrostatic pressure acting on the submerged particle. In addition to hydrostatic pressure differences on the particle, we were concerned not only about fluid momentum difference caused by solution density and flow rate but also about rotational motion due to asymmetric buoyancy driven by density gradient. The experimental results and numerical expectation proved our theoretical estimation, and here this behavior explains a new principle termed pyklinophoresis (Greek; pyk-:density, -klino-:gradient, -phoresis: migration), which enables in situ analysis of microfluidic liquid samples. An analytical model for pyklinophoresis was provided as a proof-of-concept and the analytical results of sucrose and volatile solutions were also demonstrated.

Undergraduate Student (Winter 2008 - Summer 2008):            
                                               Bumjun Kim (Bioengineering)

Teaching Assistant: Joo H. Kang

Related Articles:
     External link Microfluidic pycnometer for in situ analysis of fluids

Micro-Image Projection System: We demonstrates a micro image projection system for optoelectrofluidic manipulation of microparticles using a conventional projector. Optoelectrofluidic manipulators such as an optoelectronic tweezers (OET) is a powerful technology for microparticle manipulation using dielectrophoresis (DEP) induced by projecting and controlling dynamic optical images. In this research, we have developed a micro-image projection system using a conventional image projector for the optoelectronic microparticle manipulation. This simple, low-cost ($1000) projection system provides the performance enhancement of the optoelectronic particle manipulation. The resolution can be varied by exchanging the objective lens and adjusting focal distance. We also compare this system with the conventional lens-integrated lab-on-a-display system and analyze the main factors which cause the difference of particle motions. This new micro-image projection system can be useful for several applications using micro-image projection as well as the optoelectrofluidic microparticle manipulation.

Undergraduate Students (Winter 2008 - Spring 2008):
                            Youn-Hee Park, Sehui Lee (Bioengineering)

Teaching Assistant: Hyundoo Hwang

Related Articles:
     External link Optoelectrofluidic control of colloidal assembly

Magnetophoretic Multiplexed Immunoassays: We demonstrates a new magnetophoretic position detection method for multiplexed immunoassay using colored microspheres as an encoding tool in a microchannel. Colored microspheres conjugated with respective capture molecules are incubated with a mixture of target analytes, followed by reaction with the probe molecules which had been conjugated with superparamagnetic nanoparticles (SMNPs). Under the magnetic field gradient, the resulting microspheres are deflected from their focused streamlines in a microchannel, and respective colored microspheres are detected using color charge-coupled device (CCD) in a specific detection region of the microchannel. The color and position of respective colored microspheres are automatically decoded and analyzed by MATLAB program, and the position was correlated with the concentration of corresponding target analytes. 

Undergraduate Student (Spring 2007 - Winter 2008):
                                                   Jae-Bum Chang (Physics)

Teaching Assistant: Young Ki Hahn

Related Articles:
     External link Magnetophoretic position detection

Dielectrophoretic Oocyte Selection: A new separation method of porcine oocytes for in vitro fertilization has been described. Conventional manual selection of oocyte highly depends on the expert's experience and lacks universal standards for identifying the quality of oocyte. In this study, an electrode array chip with castellated shape was developed to evaluate dielectrophoretic (DEP) velocities of oocytes. Based on different DEP response, the selected group of oocytes that moved showed a better developmental potential than the group of oocytes that stayed, representing a higher rate of blastocyte formation and a lower rate of polyspermic fertilization. This method will open the possibility to deveop an automatic tool for oocyte selection, which would be helpful for assisted reproductive technologies such as transgenic and clonal animal production.

Undergraduate Student (Winter 2007 - Spring 2007)
                                             Do-Hyun Lee (Bioengineering)

Teaching Assistant: Wonjae Choi

Related Articles:
     External link Dielectrophoretic oocyte selection chip for in vitro fertilization
     External link
Optoelectrofluidic selection of oocytes

**(2007. 09. 05) Congratulations! Do-Hyun received a Paper Award supported by 2007 Winter/Spring KAIST URP (undergraduate research participation) program.


Microfluidic Optical Manipulator: A new programmable microfluidic platform, called lab-on-a-display, for massive parallel manipulation of live cells and microparticles using dielectrophoresis generated from a projected image of a liquid crystal display (LCD) has been developed. However, several interaction forces - among the microparticles and between target particles and device surface - interfere with the effective and non-contact particle manipulation. Here we describe experimental investigation and numerical simulation of the interactions. Finally, we suggest a new platform called 3-dimensional optoelectronic tweezers (3D OET) to prevent the particle-surface interactions by vertical focusing of the particles. In addition to these works, we have also developed a FLASH-based control program for real-time interactive manipulation.

Undergraduate Students (Winter 2007 - Spring 2007)
      Jae-Jun Kim, Young Jae Oh, Yong-Je Choi (Bioengineering)

Teaching Assistant: Hyundoo Hwang

Related Articles:
     External link Reduction of surface-particle interactions in OET
     External link Electrostatic particle-particle interactions in OET

     External link Interactive manipulation of blood cells

Electrochemical Detection: A sensitive and rapid electrochemical detection of human cardiac troponin I (cTnI) in the early diagnosis of acute myocardial infarction has been demonstrated using a microchip fabricated by assembling a surface- functionalized poly(dimethylsiloxane)(PDMS) microchannel with an interdigitated array (IDA) gold electrode. The detection experiments were performed with successive injection of cTnI, alkaline phosphatase (AP)-labeled anti-cTnI, and p-aminophenylphosphate. Then, cyclic voltammograms were obtained by the oxidation peak current proportionally to the concentration of enzymatic product, p-aminophenol. The optical packing density of anti-cTnI on the surface of the PDMS channel for the highest electrochemical signal was determined. The proper orientation and the best packing density of antibody as well as no electrode fouling contributed to the low detection limit (148 pg/ml) of cTnI within 8 min.

Undergraduate Student (Winter 2006 - Spring 2006)
                                               Bumjun Kim (Bioengineering)

Teaching Assistant: Seong-Sik Jo

Related Articles:
     External link Electrochemical detection of cardiac troponin I