Search

In this study, sustained and pH-responsive delivery of drugs were conducted using sealed microcontainers (MCs). The MCs were fabricated using a polydimethylsiloxane (PDMS) stencil. The polymer solution was filled into holes of the stencil space; then, the organic solvent was evaporated to obtain MCs. Poly(lactic-co-glycolic acid) (PLGA) was used as the material for the MCs. The MCs were sealed by covering them with a lid layer after filling the model drug—metronidazole—into the MCs. The diameter and height of the fabricated MCs were 500 and 350 µm, respectively. The drug delivery of sealed MCs was analyzed using the absorbance of the released drug while varying the pH and observing the FE-SEM image, before and after drug release. MCs are expected to be useful in various biomedical applications of drug delivery and microfluidic systems by supporting various functional materials in pH-responsive MCs.

We describe a microfluidic cell culture platform for real-time measurement of drug concentrations during cell cultivation. This is the first attempt to quantify drug concentrations during cell cultivation in real-time combining ultraviolet–visible (UV–Vis) spectroscopy with a microfluidic cell culture system in a single microfluidic chip. The microfluidic chip has two specific micro-chambers, one for spectroscopic measurements and the other for cell culture. NIH/3T3 fibroblast cells were seeded and cultured in the microfluidic chip, and then the local anesthetic lidocaine was applied and its concentration was monitored in real time. The test results showed that lidocaine negatively affected the cell growth. The lidocaine concentration was decreased due to its intake by cells for the first 3 h, after which an equilibrium concentration was reached. This is a simple but innovative method that can observe and analyze the correlation between cells and drugs in real time. The microfluidic system presented here can be a useful tool in various fields such as in cytotoxicity and drug screening studies.

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped microchannel. The microchannel was produced with polydimethylsiloxane (PDMS) using soft lithography, while the MWCNT electrodes were replicated via a PDMS stencil on indium tin oxide (ITO) glass. Moreover, the electrodes were modified with glucose oxidase and laccase by direct covalent bonding. The device was studied at different MWCNT deposition amounts and electrolyte flow rates to achieve optimum settings. The experimental results demonstrated that glucose could be determined linearly up to a concentration of 4 mM at a sensitivity of 31 mV∙mM&minus, 1cm&minus, 2.

This paper describes an investigation on the dynamic behavior of droplet formation in a microfluidic flow-focusing device (MFFD) under the effect of surfactant using a phase-field method and the Koterweg stress applied in Navier–Stokes equations. The effects of variously important parameters, such as capillary number (Ca0), water fraction ( wf), the viscosity ratio ( α), and particularly surfactant concentration ( cb), were examined. Consequently, the numerical results match the experimental ones. Additionally, the droplet formation is significantly affected by the surfactant, and the droplet size decreases with increasing cb for the whole range of both wf and Ca0. Based on the extensive study, the phase diagrams with two main modes, namely, dropping and threading, are provided. A mountain shape of the dropping mode was found, and this mode can be extended for higher wf with the presence of surfactant. In particular, new generalized correlations as a function of wf, Ca0, and cb are first proposed for predicting quickly and effectively the droplet size. Furthermore, the droplet formation depends significantly on α. With the presence of surfactant, smaller size of the droplet forms and the threading mode occurs at very high α. The results obtained in this study are very useful for understanding the dynamic behavior of droplet formation in MFFDs, which can be used in potential applications such as biomedical and drug delivery systems.

Local anesthesia is widely used in the treatment of postoperative pain. Long time duration and constant release of the local anesthetic is important for pain control. In this study, a preparation method of porous Poly (lactic-co-glycolic acid) (PLGA) microparticles loaded with local anesthetic, lidocaine was studied. Microfluidic flow-focusing device was used to prepare monodispersed microparticles. A phosphate buffer solution (PBS) was used as porogen. The geometry of microparticles was analyzed, and the drug release profile was determined by UV spectroscopy. Test results showed that porous microparticles are beneficial for sustained release of local anesthetic in long time duration over 40 days.

A soundwave is transmitted by adjacent molecules in the medium, and depending on the type of sound, it exhibits various characteristics such as frequency, sound pressure, etc. If the acoustic wavelength of the soundwave is sufficiently long compared with the size of an acoustic element, physical analysis within the sound element could be simplified regardless of the shape of the acoustic element: this is called &ldquo, long wavelength approximation&rdquo, A Helmholtz resonator, a representative acoustic element which satisfies the &ldquo, long wavelength theory&rdquo, consists of a neck part and a cavity part. The Helmholtz resonators can absorb certain frequencies of sound through resonance. To exhibit attenuation properties at ultrasound range, the Helmholtz resonator should be made into a microscale since Helmholtz resonators should satisfy the &ldquo, In this study, Helmholtz resonator inspired acoustic elements were fabricated using MEMS technology, and acoustic attenuation experiments in a water bath were conducted using various shapes and materials. As a result, the fabricated samples showed admirable attenuation properties up to ~13 dB mm&minus, 1 at 1 MHz. The results were analyzed to derive the necessary conditions for the fabrication of acoustic elements with acoustic attenuation properties in ultrasound range.

This paper reports a parametric study on mixing performance of dean flows in spiral micro-channels using the finite element method. Many important parameters such as the Reynolds number (Re), Peclet number (Pe), flow rate ratio between two species flows (α), and ratio of diffusion coefficient (β) were examined for enhancing mixing efficiency (ηmix). The numerical results matched well with those predicted by the theoretical model. In addition, mixing efficiency of dean flows in the spiral micro-channel generally increased with increasing Re, particularly at low Pe. This is in contrast to results obtained for straight micro-channels with the same channel length. Mixing efficiency (ηmix) was affected significantly by the Pe number ranging from 103 to 4 × 104, and it increases with a decrease in Pe. In addition, ηmix varied remarkably with α, and the worst point, at which the ηmix decreases by 50%, occurs when α is around 2.0. Otherwise, ηmix is shown to be influenced slightly by β. Furthermore, a new generalized correlation was proposed for predicting the pressure drop throughout a spiral micro-channel effectively. These results provide good suggestions for optimizing mixing efficiency of dean flows in spiral micro-channels, which can be used for further biological and chemical analyses.

With increasing interest in induced pluripotent stem cells (iPSCs) in the field of stem cell research, highly efficient infection of somatic cells with virus factors is gaining importance. This paper presents a method of employing microfluidic devices for dynamic cell culture and virus infection in a microchannel. The closed space in the microchannel provided a better environment for viruses to diffuse and contact cell surfaces to infect cells. The microfluidic devices were fabricated by photolithography and soft lithography. NIH/3T3 fibroblast cells were cultured in the microfluidic device in static and dynamic conditions and compared with the conventional culture method of using Petri dishes. Virus infection was evaluated using an enhanced green fluorescent protein virus as a model. Dynamic culture in the microchannel showed similar growth of cells to that in Petri dish culture, but the virus infection efficiency was four-times higher. The proposed dynamic culture system could be useful in iPSC research by providing efficient virus infection tools.

We present geometrically passive T-junction breakup as a high-throughput preparation method for polymer microcarriers. In passive T-junction breakup, an alternative method that can satisfy requirements for uniform size distribution and high production, a polymer solution droplet is split into numerous smaller droplets as it passes T-junctions, and is then polymerized into particles as solvents evaporate. Microparticles generated from poly(lactic-co-glycolic acid) (PLGA) were used to demonstrate the applicability of this method. The proposed method of droplet fission, controlled by microfluidic flow, allowed for preparation of biopolymer particles at 8000 Hz and size distribution of CV < 5%. Feasibility of the prepared PLGA microparticles was verified as microcarriers for functional materials: lidocaine, carbon nanotubes (CNTs), and 3T3 cells. The prepared microparticles showed a slower and more linear drug release profile compared to those generated using the conventional evaporation method. Highly porous microparticles were also prepared successfully using gelatin as a porogen in the T-junction breakup device.

Exoskeleton robots are used to augment human power to perform difficult tasks. These robots can generate eternal load on human muscles as training devices. In this paper, a lower-limb training device using exoskeleton is developed for muscle power augmentation during cyclic motion. A control system determines augmenting power on the human leg during pedaling motion based on the calculation of muscle activity timing. The resulting power of the exoskeleton assists cycling motion as a rehabilitation system or applies mechanical load on the leg muscles as a training system. Measurement of interaction force by the load cell on each pedal determines admittance control signal. Experiments to assist bicycle riding motion using the developed exoskeleton were conducted. From the interaction force analysis, the sources of errors in the motion control are found, and the application-specific problems are discussed. Given that the exoskeleton robot can control hip and knee joint independently, the proposed system can be extended for assisting various motions in daily life, including walking rehabilitation.

Applying mechanical pressure on a solid boundary contact using a thin porous layer has been found to reduce the pore size and porosity near the wall region, limiting the flow and mass transport properties. This reduction may affect the overall performance of devices such as the electroosmotic pump that generally uses a porous media with constant porosity in an electric field. Therefore, to improve the performance of such devices, a composite porous layer that uses a combination of different porosity value based on the location in the porous domain, is employed with a higher porosity near the wall region than that in the central region. In this study, a numerical simulation is conducted to investigate the fluid dynamic and mass transport characteristics using a composite porous layer with electroosmotic flow. A comparison of the results with the pressure-driven flow shows the effectiveness of the composite porous layer in compensating for the loss of porosity and in improving device performance. The proposed methodology may also enhance the performance of green energy devices such as fuel cells.

The application of pressure in the assembly of devices containing thin porous layers has shown significant effects with the presence of a solid boundary contact. During this process, pore diameters of the thin porous layers are reduced. Thus, the porosity in the near wall region is effectively reduced. The reduced porosity significantly lowers the overall performance of the devices because of the limited fluid dynamic variables. A new method for the positional variation of porosity is proposed to compensate the fluid dynamic disadvantages and mass transport characteristics in the industrial devices such as filters, porous electroosmotic pump and fuel cells. In the present study, the novel method introduces a composite porous layer with high porosity in the outer region rather than in the central region of the porous media. A three-dimensional numerical simulation is performed to investigate the effects of this positional variation of porosity and the performance of the composite porous layer. A reasonable increase in flow rate is found in the wall region and in the central region, depending on the increment in the porosity in the outer region and on the orientation of the porous layer to the fluid flow.

The manufacture of helical pinion gears has involved machining processes such as hobbing and shaving to achieve the required dimensional accuracy. However, these conventional processes have some disadvantages such as excessive material loss, low productivity, high-energy consumption, and high carbon emissions. To overcome these problems, a cold extrusion process is applied to the manufacture of helical gears. In this study, we analyze the environmental effects of the cold extrusion process, designed for the sustainable production of helical gears. We quantitatively analyze the environmental effects of the conventional machining and cold extrusion processes, using the Life Cycle Assessment technique in accordance with ISO 14000. This analysis includes the energy consumption and carbon emissions for a helical gear manufactured using the conventional machining processes and those of single- and double-type gears manufactured using the cold extrusion process. Moreover, the material properties of the extruded helical gears are compared with the conventionally machined gears. In conclusion, the extruded gears exhibited a higher strength while consuming less energy during their manufacture than the gears manufactured using the conventional machining processes. Further, this alternative process is more cost effective as it generates less waste and exhibits high productivity compared to the conventional machining processes.

We present a 512-microchannel geometrical passive breakup device for the mass production of microdroplets. The mass production is achieved through the passive breakup of a droplet into two droplets. The microchannel geometry in the microfluidic device was designed and optimized by focusing on stable droplet splitting for microdroplet preparation and minimizing the hydraulic resistance of the microchannel for achieving high throughput, the minimization of hydraulic resistance was achieved by employing analytical approaches. A total of 512 microdroplets could be prepared from a single liquid plug by making the liquid plug pass through nine sequential T-junctions in the microfluidic device, which led to the splitting of droplets. The microfluidic device was fabricated using conventional photolithography and polydimethylsiloxane (PDMS) casting. We estimated the performance of the microfluidic device in terms of the size distribution and production rate of microdroplets. Microdroplets with a diameter of 40.0 &plusmn, 2.2 &micro, m were prepared with a narrow size distribution (coefficient of variation (CV) &lt, 5.5%) for flow rates of disperse (Qd) and continuous phase (Qc) of 2 and 3 mL/h, respectively. Microdroplet production rates were measured using a high-speed camera. Furthermore, monodisperse microdroplets were prepared at 42.7 kHz for Qd and Qc of 7 and 15 mL/h, respectively. Finally, the feasibility of the fabricated microfluidic device was verified by using it to prepare biodegradable chitosan microspheres.

The original version of this article unfortunately contains a mistake. The acknowledgement section of the above article is incorrect. The correct acknowledgements are as follows

In this presentation, we propose a fabrication method of PDMS stencil to apply into a localized culture of NIH/3T3 cells. PDMS stencil was fabricated by nitrogen gas blowing and soft lithography from preparing SU-8 master mold by photolithography. PDMS stencil pattern was production of the circle size 20 to . In the culture test of PDMS stencil, a stencil was placed on a glass disk. The NIH/3T3 cells were successfully cultured into micropatterns by using the PDMS stencil. The results showed that cells could be cultured into micropatterns with precisely controlled manner at any shapes and specific size for bioscience study and bioengineering applications.

A light scanning device with two microfluidic hemicylindrical lenses was demonstrated for adjustable laser sheet beam scanning applications. An elastomeric hemicylindrical lens, whose focal length can be adjusted by control of the applied fluidic pressure, was fabricated by application of the pressurized casting process on polydimethylsiloxane (PDMS) obtained from a prepared microsized mold. The hemicylindrical lens consisted of a thin membrane, a liquid chamber and a microchannel. The applied fluidic pressure deformed the lens membrane and changed the lens shape. The change of the lens shape allowed beam shape transformation or beam scanning according to the relative size of the beam to the lens. By orthogonally placing two microfluidic lenses of different sizes, 1 mm × 5 mm and 3 mm × 15 mm, respectively, a spot laser beam from a 200μm-large pinhole was transformed into laser sheet, and then the laser sheet was scanned. The relationship between the lens properties, including lens curvature and laser beam shaping according to different applied pressures on the lens, were systematically investigated. Laser beam scanning properties of the microfluidic light scanning device were also characterized for various applied pressures and offset distances.

In the present study, we experimentally investigated the roll stability recovery performance of a vehicle at various tilting angles. The vehicle was ultimately targeted to contain a velocity-field measurement system in underwater conditions, which should confirm stationary buoyancy during measurement. We employed two small gear-rack ax mountings on a weighted mass as the actuating system inside the bluff-body. Speed and movement were feedback controlled by the activating electronic motor system. The feedback algorithm used tilting action signals from an inclinometer sensor installed in the central region of the vessel shell. As a result, the bluff-body vessel effectively recovered self-stabilizing positions against the tilting action.

A direct patterning for a barrier rib using the roll-imprinting process is getting more interests in display manufacturing fields. Master roll patterning is one of the important issues in the roll-imprinting process. In this study, a novel fabrication process of micro-patterning on a roller surface by applying the photolithography process is studied. Because the roller surface was a cylindrical shape, the designed pattern was made by using a film mask. Special jigs and roll holder were designed and used for the photolithography on the roll substrate. The roll patterning results showed a feasibility of the proposed method for the photolithography on the roll’s surface.

We present a novel microvalve for the treatment of a pathological condition, i.e., hydrocephalus. This microvalve is made of polydimethylsiloxane/Parylene composite layer which has a 3-D dome petal shape. This geometry enables the microvalve to rectify fluid flow in the forward and backward directions. New microfabrication techniques such as dome-shaped SU-8 mold fabrication and excimer laser machining for valve opening have been investigated to build the proposed microvalve. The pressure drop versus flow rate characteristics of the fabricated microvalve was investigated through in vitro flow tests. The flow test results showed that a 10 × 10 microvalve array with a cross-cut opening shape (200 × 60 μm) was found to be optimal for the treatment of hydrocephalus.

A method for fabrication of flexible stencil was studied. Flexibility of the stencil allows micropatterning on a curved surface by material deposition or material removal (etching) through patterned hole of the stencil. In this study, low mechanical stability of the thin stencil membrane was improved by bonding the membrane with rim supporter which is thick and strong enough for easy handling of the stencil. Both of the membrane and rim structure were made of elastomer, PDMS using molding process from SU-8 master mold. The application test of shadow deposition and etching on underlying nonplanar surface using the fabricated flexible stencil mask showed the feasibility of the suggested technique into micro- patterning on a curved surface.

In micro electrochemical machining(micro-ECM), it is important to measure and control the potential of a tool electrode and a workpiece electrode because electrochemical reaction rate depends on the potential of the electrodes. When the electrode potential was measured against a reference electrode, the error of measured electrode potential could be minimized by proper tool electrode design. In this paper, multi-function electrodes consisting of a tool electrode and a reference electrode was fabricated by micro fabrication techniques. The machining conditions in micro-ECM using multi-function electrodes, such as pulse voltage parameters and electrode potential, were investigated.

We report the results of diffuser lithography applied to a negative-type thick photoresist to fabricate 3-dimensional microstructures suspended on supports. When UV light passes through a diffuser film, the direction of the light is randomized because of the irregular surface of the diffuser. By exposing through a diffuser on a Cr-mask, a circular or an elliptical cross-section of exposed region can be formed on a spin-coated photoresist. When applied to a negative-type thick photoresist, diffuser lithography gives a 3-dimensional circular cross-section of the exposed and cross-linked regions, which could be used for making suspended microstructures. The size of the exposed region has been controlled by the dose of the UV light. The current study clearly shows that the depth of exposed region of photoresist is affected by the geometry of the pattern. By controlling the depth of the exposed region using different pattern size, beam structures suspended on the support structures could be fabricated by single exposure process. The characteristics of the diffuser lithography process were investigated on a negative type photopolymer, SU-8, with different doses of UV-light and different geometry.

Biological flows, especially blood flow, have attracted a great deal of attention from fluid engineering and hemodynamic investigation fields with advances in bio-technology. The flow of blood carries dissolved gases, nutrients, hormones, and metabolic waste through the circulatory system in the human body. In the present study, the characteristics of blood flow inside a microchannel are investigated by using a micro-particle image velocimetry (micro-PIV) and an optical image processing technique. The motion of red blood cells (RBCs) was visualized with a high-speed CCD camera. The microchannel is made of polydimethylsiloxane (PDMS) material and a slide-glass is attached to the top. The thickness of the margin cell depletion layer is calculated from an acquired raw image through the image processing method, with variations in microchannel width.

SU-8 is a photoplastic polymer with a wide range of possible applications in microtech- nology. Cantilevers designed for atomic force microscopes were fabricated in SU-8. The mechanical properties of these cantilevers were investigated using two microscale testing techniques: contact surface profilometer beam deflection and static load deflection at a point on the beam using a specially designed test machine. The SU-8 Young's modulus value from the microscale test methods is approximately 2-3 GPa.

This paper presents a method to analyze the 3-dimensional form error of a ball-end milled surface due to the elastic compliance of the cutting tool. In order to estimate the form error in various cutting modes, the cutting force and the cutter deflection models including the effect of the surface inclination were established. The cutting forces were calculated by using the cutter contact area determined from the Z-map of the surface geometry and the current cutter location. The tool deflection responding to the cutting force was then calculated by considering the cutter and the holder stiffness. The cutter was modeled as a cantilever beam consisting of the shank and the flute. The stiffness of the holder was measured experimentally. Various experimental works have been performed to verify the validity of the proposed model. It is shown that the proposed method is capable of accurate prediction of cutting forces and the surface form error.

A release technique that enables to lift microfabricated structures mechanically off the surface without using wet chemistry is presented. A self-assembled monolayer of dodecyl-trichlorosilane forms a very uniform /spl sim/1.5-nm-thick anti-adhesion coating on the silicon dioxide surface, on full wafer scale. The structural layers are formed directly onto the organic layer. They consist here of a 100-nm-thick aluminum film and a high-aspect ratio photoplastic SU-8 structure. After the microfabrication the structure can be lifted off the surface together with the aluminum layer. This generic technique was used to make a variety of novel structures. First, aluminum electrodes that are embedded in plastic are made using lithography, etching and surface transfer techniques. Second, using a patterned monolayer as defined by microcontact printing, resulted in a spatial variation of the surface adhesion forces. This was used to directly transfer the stamped pattern into a metal structure without using additional transfer etching steps. Third, the monolayer's ability to cover surface features down to nanometer scale was exploited to replicate sharp surface molds into metal coated photoplastic tips with /spl sim/30-nm radii for use in scanning probe instruments such as near-field optical techniques. The advantage compared to standard sacrificial layer techniques is the ability of replication at the nanoscale and the absence of etchants or solvents in the final process steps.

We present a fabrication method using polydimethylsiloxane (PDMS) stencils and solvent evaporation to prepare microcontainers with a desired shape made from a biodegradable polymer. Poly(lactic-co-glycolic acid) (PLGA) was used for preparing microcontainers, but most polymers are applicable in the proposed method in which solvent evaporation is used to construct microstructures in confined spaces in the stencil. Microcontainers with various shapes were fabricated by controlling the stencil geometry. Furthermore, a porous structure could be prepared in a micromembrane using water porogen. The porous structure was observed using a field emission scanning electron microscope and mass transfer across the porous membrane was examined using a fluorescent dye. The flexibility of the PDMS stencil allowed the fabrication of microcontainers on a curved surface. Finally, it was demonstrated that microcontainers can be used to contain a localized cell culture. The viability and morphology of cultured cells were observed using confocal microscopy over a period of 3 weeks.

We present a 1600 parallel microchamber microfluidic device for fast sample array preparation using the immiscibility of two liquids. The trapping efficiency and size of the arrayed sample in the microchambers of a parallel microfluidic device were analyzed at various flow rates. The trapping efficiency of the sample was also inspected according to the position of the microchamber. Samples were successfully arrayed using the device. The trapping efficiency of the sample was 98.69% at 1 mL/h. The trapping efficiency and diameter of the sample decreased as the flow rate increased. Trapping efficiencies also changed according to the position of the microchambers. As the distance of the microchambers from the inlet increased, the sample trapping efficiency decreased. This tendency occurred more clearly at higher flow rates.

The cutting force in ball-end milling of sculptured surfaces is calculated. In sculptured surface machining, a simple method to determine the cutter contact area is necessary since cutting geometry is complicated and cutter contact area changes continuously. In this study, the cutter contact area is determined from the Z-map of the surface geometry and current cutter location. To determine cutting edge element engagement, the cutting edge elements are projected onto the cutter plane normal to the Z-axis and compared with the cutter contact area obtained from the Z-map. Cutting forces acting on the engaged cutting edge elements are calculated using an empirical method. Empirical cutting mechanism parameters are set as functions of cutting edge element position angle in order to consider the cutting action variation along the cutting edge. The relationship between undeformed chip geometry and the cutter feed inclination angle is also analyzed. The resultant cutting force is calculated by numerical integration of cutting forces acting on the engaged cutting edge elements. A series of experiments were performed to verify the proposed cutting force estimation model. It is shown that the proposed method predicts cutting force effectively for any geometry including sculptured surfaces with cusp marks and a hole.

In this study, an air-knife system was developed for the automated fabrication of polymer microstencils with microscale perforated patterns. Blowing compressed N2 gas through the air knife provided a uniform laminar gas flow of high intensity suitable for perforating holes in the stencil. The polydimethylsiloxane (PDMS) stencil was replicated from a master mold prepared by photolithography. When the prepolymer of PDMS was spin-coated onto the master mold, a thin layer of the prepolymer remained on top of the master's structure and consequently prevented the formation of the perforated patterns. This residual layer was easily removed by the presented air knife. The air-knife system controlled the flow rate of N2 gas and the conveying speed of the master mold; therefore, the system possessed high reproducibility compared to manual gas blowing. Its use reduced the fabrication time for perforated biocompatible polymer microstencils, allowing for their mass production via an automated system. The validity of this suggested method was proven through experiments and was evaluated by application in various fields.

A novel method to prepare a very thick master mold for poly(dimethylsiloxane) (PDMS) casting was investigated by using a hydrogel ultraviolet (UV) curing process through a film mask. A simple process of dispensing of hydrogel, UV curing through a photomask and rinsing enabled the construction of micro-hydrogel structures in a fast manner. These hydrogel structures can be used as a mold for PDMS casting for PDMS fluidic chip fabrication. This method allows the fast construction of very thick micro-structures more than 1 mm. The characterizations about vertical sidewall and adhesion enhancement between the substrate and micro-structures were studied. The application of a PDMS fluidic chip, which was prepared from the hydrogel mold by PDMS casting, to some fluidic flow rate tests was demonstrated. This method is fast and simple to prepare a PDMS casting mold at low cost and can be applied in micro-fabrication of biochemical chips and micro-fluidic devices.

In this study, drop-on-demand system using piezo-elecrtric inkjet printers was employed for preparation of collagen microspheres, and its application was made to the HepG2 cell-laden microsphere preparation. The collagen microspheres were injected into beaker filled with mineral oil and incubated in a water bath at 37℃ for 45 minutes to induce gelation of the collagen microsphere. The size of collagen microsphere was 100μm in diameter and 80μm in height showing spherical shape. HepG2 cells were encapsulated in the collagen microsphere. The cell-laden microspheres were inspected by the microscopic images. The encapsulation of cells may be beneficial for applications ranging from tissue engineering to cell-based diagnostic assays.