We propose a prototype of silicon-on-glass microchip for protein detection by bead-based affinity chromatography. The microchip has five channels integrated by composing one beads reactor per one channel. Especially, an effective protein analysis mechanism is presented where the three protein-pretreatment processes are simultaneously performed on a single beads reactor: selective detection (purification / sensing), pre-concentration and protein digestion. Since the five channels are closely spaced in parallel on the microchip, it is possible to inspect the five different detection results on real-time in a single microscope image. The microchip is fabricated on silicon-on-glass (SiOG) to make a mechanically strong and vertically transparent structure for efficient fluid interconnection and fluorescence detection, respectively. Within the microchip, the grid-type filter is formed on channel output to physically trap 38 ~ 50 μm diameter microbeads. The dimension of one grid is 30 × 30 μm2. The volume flow rate was investigated experimentally on the case of bead-packed chamber, and the resulted value was compared to that of the case of hollow chamber. In this research, we used self-cleavage free aptazymes as detection ligands immobilized on polystyrene microbeads. The target proteins are firstly on-chip concentrated and fluorescence-detected (confocal microscopy), and secondly checked off-chip by using MALDI-TOF. If the two analyses are used cooperatively, it is expected that the accuracy in diagnostic analysis will be enhanced in biosensing system. Especially by using this free aptazymes system, we don't need to consider the requirement of fluorescence tagging and the difficulty of eluting antibody-bound proteins from microbeads without bad effects of harsh elution conditions in protease treatment. We analyzed the on-bead detection of HCV replicase and HCV helicase respectively by measuring fluorescence intensities at different concentrations, and also performed a selectively detection of HCV helicase from protein mixtures.
In this study, a new method is described for integrating an electrospray ionization interface to a mass spectrometer with a capillary electrophoresis channel. We have fabricated the ESI-MS device composed of the metal emitter tip, allowing the generation of an efficient nanospray for protein detection, and CE separation channel monolithically in a glass microchip. A triangular-shaped gold emitter tip was formed by electroplating at the end of the separation channel. As an ESI source, this emitter structure aided the formation of a stable Taylor cone. It is easily fabricated by MEMS technology and more robust than that of silica or polymer recently reported. Moreover, this approach is less involved than applying a conductive coating to the exit end to establish electrical contact. As such, the interface is less dependent upon the longevity or durability of such coating, factors that have been consideration in the sheathless interfaces. The spraying stability was evaluated and the ESI-MS experiment was performed by spraying standard peptides for mass spectrometric analysis. The spraying was stable, with a relative standard deviation of 2.9%. The CE/ESI-MS analysis was performed by separating and spraying standard peptide mixture of Bradykinin 1-5, Bradykinin 1-8, and Angiotensin I. Each peptide was separated successfully and singly-charged peaks and doubly-charged peaks of each peptide were detected, respectively. Direct comparisons with conventional ESI-MS system using glass or fused silica emitters showed very similar performance with respect to signal intensity and stability.
This paper describes thermal denaturation and trypsin digestion of protein on a microchip as an alternative application of a temperature controllable microchip. Analysis of the protein of small volume and low concentration, which is impossible in macro scale, could be possible with the fairly reduced process time using the proposed temperature controllable microchip. We optimized the parameters concerning thermal denaturation on a microchip such as thermal denaturation temperature, thermal denaturation time, digestion time and concentration of protein using BSA(bovine serum albumin) as a reference sample. Then we applied the optimized parameters to the other proteins (ovalbumin, myoglobin, hemoglobin, cytochrome C, Ubiquitin). The proposed method on a microchip in this paper needed an even shorter reaction time, smaller volume of sample and smaller concentration of sample compared to the previously presented marco scale thermal denaturation and trypsin digestion method. We could successfully acquire the thermally denatured protein in 1 minute at 85°C and the digested peptides in 10 minutes at 37°C with 3 μl/0.2 μM protein. The acquired average sequence coverages are range from 24 to 57% for the test proteins, which are sufficient for the protein identification in practical use.
This paper presents the design, fabrication, and testing of a single crystalline silicon (SCS) micromirror array (MMA) for peptide synthesis applications. Also, preliminary peptide synthesis experiments are presented for the proof of MMA performance. The application specific MMA had a simple fabrication process (only 3 photomasks), large mirror size (210x210μm2) and proper separation (60um). In order to obtain reliable structure and characteristics, we incorporated silicon on insulator (SOI) wafer and stepper photolithography. To maximize the pull-in voltage uniformity, sequential designing steps were described considering design limitations. The proposed fabrication process showed that the fabrication yield was very high up to 91.3%. The total array size consisted of 16 x 16 mirrors and tilting angle was 8.5° for left side or right side operations. The surface roughness was very low and less than 4 nm. The switching time of 156 μsec was reasonable since the exposure time during peptide synthesis was a few seconds. The fabricated MMA had a little pull-in voltage non-uniformity because of dimensional non-uniformities or fabrication errors. We have implemented an automated pull-in voltage measurement setup for verifying the pull-in voltage variation among the array. The measured pull-in voltage among 256 mirrors had the average of 96.99 V and the standard deviation of 2.12 V. The fabricated and analyzed MMA was adapted to the automatic peptide synthesis system and the peptide synthesis experiments showed that the SCS MMA improved the synthesis performance.
We fabricated a scanning mirror and optical benches monolithically in a silicon substrate using DRIE process and trench passivation by capillary filling. The micro scanning mirror, actuated by comb electrodes and supported by torsional spring, was fabricated with the optical benches in single crystalline silicon for the integration of optical fibers and ball lenses. Micro prism was adopted for high sensitive fluorescence detection system with scanning mirror. The excitation beam needs to be focused mainly on the slanted area of the micro prism in order to increase optical power efficiency. Considering beam collimation for high power efficiency, beam steering on the micro prism, and simple integration with the micro prism, we proposed silicon scanning mirror having slanted reflective plane and optical benches monolithically fabricated in the same silicon substrate. Reflective surface of the proposed scanning mirror makes parallel incident laser to the substrate be normal downward to the plane of substrate so that optical alignments become simple just by the alignment of scanning mirror’s and micro prism’s substrate. In this research the slanted angle of mirror plane is (-) 54.74 degree inclined instead of 45 degree because the scanning mirror was fabricated in single crystalline silicon (100)-oriented wafer using KOH wet process for the easy fabrication and fast feasibility test. The scanning mirror scans the laser one dimensionally by the actuation so that laser spot can be line-shape on the prism plane. The mirror is a pyramidal structure actuated by comb electrodes and torsion spring. The designed scanning mirror is 2165 x 778 μm2 in an upper plane and it has a slanted trapezoidal mirror reflective surface, which size is about 2000 x 1600 μm2, considering the micro prism dimension. The maximum deflection angle of the scanning mirror was 7° when 16 Vpp square type voltage is applied to the comb electrodes at resonant frequency.
Two dimensional micromirror array(MMA) is designed and fabricated to be used as a spatial light modulator for biochip fabrication. The optical projection system is setup using the MMA for maskless photolithography process, which is applied to photochemical surface modification. The photoresist (AZ1512) pattern is fabricated by the MMA projection in the maskless photolithography system, which consists of MMA and other optical components like projection lens. The patterned PR on a chip substrate is analyzed to improve pattern edge definition. The parameters of the optical system, which are lens location, incident angle of the UV light and the MMA location, are adjusted to obtain fine pattern edge definition by the MMA deflection. To immobilize proteins on the specific surface regions of a chip substrate to make protein patterning, nitroveratryloxycarbonyl(NVOC) group is used as a photolabile protecting group. The surface which is protected by NVOC group, is selectively irradiated by UV illuminator using the MMA. After removing the NVOC group, FITC(fluorescein isothianade) is tagged to the NVOC-cleaved site to find out the photo-cleavage condition of NOVC group by UV irradiation in the maskless photolithography system. Using the photocleavage condition, biotin was coupled to the NVOC-cleaved site. Then, we could obtain streptavidin-patterned surface.
The comb actuator deformed by microloading effect in DRIE process generally has í«Lí» shape comb electrodes. Therefore, the actuator shows nonlinear differential driving characteristics. A simple modeling is suggested and simulated to explain the driving characteristics. For modeling convenience, the damaged comb electrode is assumed to be a simple í«Lí» shape. According to the modeling, the resonant frequency is estimated to increase as the bias voltage increases. The static displacement curve shows í«Sí» shape.
This paper describes the design, fabrication and experiments of a micromirror array driven by electromagnetic force for right angle beam reflection to the vertical direction of the substrate. The device was fabricated using aluminum surface micromachining combined with nickel electroplating. The micromirror has couple of torsional springs enough long for 45 degree rotation, which angular deflection is necessary for right angle beam reflection. Also micromirror has a magnetic material for electromagnetic operation, and it has a mechanical stopper for angular deflection control. The main structural material is evaporated aluminum, and magnetic material is electroplated nickel. Thick photoresist is used as a sacrificial layer, and it is removed by oxygen plasma process. Electromagnetic characteristics were measured to find that about 10kA/m magnetic field intensity is needed for 45 degrees angular deflection. 25V to approximately 50V clamping voltage is required for selectively operation between the array within the external magnetic field. The dynamic response measurement was fulfilled using He-Ne laser and position sensitive diode (PSD). The lapsed time to reach 45 degrees is less than 0.5ms. But upward spring bending prevents the stopper from touching the substrate, so some oscillations corresponding to natural response is observed.
The precise position control of an optic element is a quite important technology and thus has many applications in modern optic system. This paper describes the optic system composed of a micro lens and positioning actuator. Two types of the micro Fresnel lens and the micro spherical lens are fabricated by using UV-lithography and reactive ion etching (RIE). The monolithic spherical lens is fabricated through the photo-thermal technique of photoresist. 3 mm-focal length with 246 micrometers -diameter Fresnel lens and 31 micrometers - focal length with 50 micrometers -diameter spherical lens are fabricated. The XY-stage is proposed as a control actuator, which is a 2-degree of freedom-stage structure with a pari of perpendicularly combined comb drive. The travel range of the micro XY-stage is measured 48 micrometers in each X and Y direction. The mechanical interference between X- and Y-axis is negligible. Integration process of these two parts is based on the concept of in-situ process using anodic bonding. This device is expected to be applicable for the fields of optical pickup, light beam aligning and optical signal sensing.
A vertical spring-type micromirror was fabricated using a SiO2 shielding screen structure. The fabricated vertical springs are well defined but the mirror plate is bent because the mirror plate is composed of SiO2 and aluminum layers. To obtain a flat mirror plate, the stress of SiO2 and aluminum is analyzed and the bending deflection of mirror plate's edge is measured. The measured deflection varies with the thickness of aluminum. Another SiO2 layer on the mirror aluminum improved the flatness of mirror plate.
Micromirrors supported by S-shape girders were fabricated and their angular deflections were measured using a laser- based system. A micromirror consists of a 50 micrometers X 50 micrometers aluminum plate, posts and an S-shape girder. Two electrodes were deposited on two corners of the substrate beneath the mirror plate. 50 X 50 micromirror array were fabricated using the Al-MEMS process. The electrostatic force caused by the voltage difference between the mirror plate and one of the electrodes causes the plate to tilt under the girder touches substrate. Bias voltage of the mirror plate is between 25 approximately 35 V and signal pulse voltage on the electrodes is 5 V. A laser-based system capable of real-time two-dimensional measurements of the angular deflection of the micromirror was developed. The operation of the system is based on measuring the displacement of a HeNe laser beam reflecting off the micromirror. The resonance frequency of the micromirror is 50 kHz when the girder touches the substrate and it is 25 kHz when the micromirror goes back to flat position, since the moving mass is about twice of the former case. The measurement results also revealed that the micromirror slants to the other direction even after the girder touches the substrate.
The variable focusing lens is designed and fabricated, which can work as human eye's crystalline lens. The lens consists of glass diaphragms, microchannels and working fluid. The chamber between two glass diaphragms is filled with the working fluid. Refractive index matching oil such as silicon oil can be used as working fluid, which is pumped into or out of the chamber through the microchannel. The curvature of the lens can be changed by the oil pressure, which is built by micropump outside. The change of curvature of the lens produces the focal plane shift. In addition, both convex lens and concave lens can be realized by pressurized working oil. Commercial micropump is used for the test of a fabricated variable focusing lens. Designed diameter of the variable focusing lens is 10 mm. Thickness of the glass diaphragm is 50 micrometers . Glasses are bonded to <100> silicon and thinned through CMP (Chemical Mechanical Polishing). The chamber and channels are formed by silicon wet etching. Mechanical characteristics (such as deflection of the glass diaphragm by the oil pressure) and optical characteristics (such as focal plane shift) of the variable focusing lens are estimated by modeling. The variable focusing lens can apply to optical pickup, CCD camera and microscope etc.
In the fields of adaptive optics and pattern recognition system, SLM is used to modulate the phase and amplitude of incident light in order to correct aberration in an optical system through active control of mirror array. In this paper, a micro spatial light modulator (SLM) array, which has one hundred of micro SLM, that is to say, 10 X 10 array, for phase and amplitude modulation of incident light is designed and fabricated using surface micromachining technology. In order to maximize the fill factor and minimize diffraction effect, hidden spring structure is used. A designed micro SLM is composed of a mirror plate, upper electrode, five support posts, and bottom electrode. The spring structures are composed of double crab leg spring for phase modulation and torsional spring for amplitude modulation. The micro SLM is actuated by electrostatic force generated by electric potential applied between upper electrode and bottom electrode. In case of phase modulation, the maximum deflection length of mirror plate is 4 micrometers and in case of amplitude modulation, it is designed to be capable of tilting +/- 5.4 degree(s) to reflect incident light.
This paper describes the design and fabrication of surface- micromachined micromirror array with hidden joint structures. Instead of using elastic spring components, such as cantilevers, flexure beams, and torsion hinges, we have used joint structure composed of pin and staples to support the mirror plate. The position of the joint structure, under the mirror plate, makes large active surface area possible. Arrays of 100 X 110 micrometers 2 sized micromirrors with two different staple shapes are designed and fabricated. These flexureless micromirrors are driven by electrostatic force between mirror plate and address electrode under it. As the mirror plate has discrete deflection angles the device is well suited for spatial light modulating purpose. Four-level metal structural layers and semi-cured photoresist sacrificial layers are used in the fabrication process and sacrificial layers are removed by dry release process using oxygen plasma. Performance characteristics are measured by applying voltage difference between the ground electrode, which contacts the mirror plate via support post, and an address electrode.
A silicon based micro mirror array is a highly efficient component for use in optical applications as adaptive optical systems and optical correlators. Many types of micro mirror or micro mirror array have been studied and proposed in order to obtain the optimal performance according to their own purposes. A micro mirror array designed, fabricated and tested in this paper consists of 5 X 5 single layer polysilicon-based, electrostatically driven actuators. The micro mirror array for the optical phase modulation is made by using only two masks and can be driven independently by 25 channel circuits. About 6 (pi) phase modulation is obtained in He-Ne laser ((lambda) equals 633 nm) with 67% fill-factor. In this paper, the deflection characteristics of the actuators in controllable range were studied. The experimental results show that the deflection characteristics is much dependent upon a residual stress in flexure, the initial curvature of mirror due to stress gradient and an electrostatic force acted on other element except for mirror itself. The modeling results agree well with the experimental results. Also, it is important to fabricate a flat mirror that is not initially curved because the curved mirror brings a bad performance in optical use. Therefore, a new method to obtain the flat mirror by using the gold metallization in spite of the residual stress unbalance is proposed in this paper.
A bulk-micromachined interdigitated comb actuator supported by surface-micromachined polysilicon springs is proposed and fabricated for excitation of resonating momentum. The excitation force electrically generated by the interdigitated comb pair with a 420 height of (110) wafer is more effective than that obtained using a comb pair with a few height fabricated by a surface micromachining technique. The geometry of the interdigitated comb finger pair is 420 high, 20 wide, 5 apart from the neighboring interdigitated comb finger, respectively. A (110) oriented 420-thick Si wafer is used to fabricate the interdigitated comb electrode array using the technique of anisotropic bulk etching in KOH aqueous solution. A 5-thick phosphorous-doped LPCVD polysilicon film is used for fabrication of the flexures of the comb actuator using the technique of reactive ion etching. Repetition of the LPCVD Si3N4 film deposition and reactive ion etching process builds a Si3N4 structure, which envelopes and protects the released polysilicon structure from KOH aqueous etchant without an additional mask for passivation patterning. Using a double-sided aligned fabrication technique realizes not only polysilicon flexures formation on both sides of the actuator but also removal of two slant (111) planes in concave corners of the interdigitated comb finger array, which appear during (110) Si orientation-dependent etching and limit the interdigitated comb actuator design.
A simple electroplating surface micromachining process for fabricating freestanding microstructures using UV lithography of thick photoresist and double electroplating has been developed. Compared with the conventional surface micromachining process, this process can be used to fabricate various shapes of freestanding 'out-of-plane' microstructure. In this process, two different materials electroplated continuously in a single mould are used as a sacrificial and a structural layer respectively. Fabrication of different shapes of 3D microstructures using controlled overplating on the patterned plate base electrode array has been reported, and this method was applied to form a 3D sacrificial layer. Shape of the sacrificial layer can be varied by changing width and space of the patterned plating base electrodes. After selective etching of the sacrificial layer we can obtain a released structure, the shape of which is automatically determined by that of sacrificial layer. Released gap and thickness of the structure are easily controlled by only changing electroplating time. Using this process, a simple microactuator that is able to move in the vertical direction and have inclined side-support beams is successfully fabricated. This technique can be applied to fabricate a novel type of surface micromachined actuating component.
Test equipment for the development and mass production of micromirror array have been devised. Test equipment for the static and dynamic response of a single micromirror consists of HeNe laser, lenses, XY stage, CCD camera, position- sensitive photodiode and PC. It can be used to measure reflectance, tilt angle--input voltage relation, response time and resonant frequency, in the developing stage. It can also check the lifetime and uniformity of mirror quality over the wafer. Test equipment for the evaluation of micromirror array consists of CCD camera, lenses, XY stage, video signal processor and PC. It can classify the error- state of micromirror, generate statistical data and map of the position of abnormal micromirrors. The test results are shown on the monitor as a map that shows the error state, position and statistical data. It takes about 90 seconds to evaluate 50 X 50 micromirror array.
A standard semiconductor process and a chemical immobilization of the functional groups to the glass surface were used to fabricate the biocompatible base substrates for the cell biosensor with specific micropatterns of amine groups and, thereby to create the extracellular protein island of the defined shape and size that support a single cell attachment. Defined size, 15 - 100 micrometer in each side, of rectangular pattern was obtained by the bulk- etching of n-type [100] Si wafer. After etching process of glass with concentrated HNO3, the glass substrate covered with the silicon mask was exposed to hexamethyldisilane vapor at 200 degrees Celsius for 30 minutes to couple the silane. Human umbilical vein endothelial cells were cultured on the micropattern after crosslinking the human fibronectin to micropatterned silane. It was possible to adhere endothelial cells in a predetermined location and shape with this technique. The responsibility of adhered endothelial cells to physical stress, such as blood flow, was limited by the controlling the polymerization of actin cytoskeleton and morphology of the cell. The simple laminar flow chamber was developed to exposure defined laminar shear stress on the micropatterned endothelial cell array. Fabrication of biocompatible micropattern with this method is experimentally simple and highly reproducible for application of the cell biosensor for physical and chemical applications.
A 100 X 100 micrometers 2 aluminum micromirror is designed and fabricated using a thick photoresist as a sacrificial layer and as a mold for nickel electroplating. The micromirror is composed of aluminum mirror plate, two nickel support posts, two aluminum hinges, and two address electrodes. The aluminum mirror plate, which is suppoorted by two nickel support posts, is overhung about 10 micrometers from the silicon substrate. We use thick photoresist to obtain 10 micrometers thick sacrificial layer and electroplate nickel to obtian 10 micrometers height support post. The aluminum mirror plate is actuated like a seesaw by electrostatic force generated by electrostatic potential difference applied between the mirror plate and the address electrode. We use reactive ion etching to release the micromirror plate from the silicon substrate. The edge of the mirror plate landed on the substrate (maximum deflection) when the potential difference between the mirror plate and the address electrode was 35 volts, and the mirror was released from the substrate when the potential difference reduced to 22 volts.
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