• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.809-809
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• 2013

We report a new method for highly controllable local patterning of a hydrogel on microfabricated cantilevers and fabrication of all hydrogel microcantilevers. We constructed a dynamic mask based photolithography setup using a commercial beam projector, a 3-axis microstage and other optical components. Dynamic masks generated from the beam projector controlled the shape, size, and position of hydrogel patterns while the 3-axis microstage mainly controlled the thickness of hydrogel patterns and hydrogel microcantilevers. Using the constructed setup, polyethyleneglycol diacrylate (PEGDA) was patterned on microfabricated cantilevers in a highly controlled manner. Currently, the smallest PEGDA patternable is a 5-${\mu}m$-diameter circle with a thickness of ~$10{\mu}m$. To confirm thicknesses of patterned PEGDAs on silicon microcantilevers, resonance frequencies of microcantilevers were measured before and after each PEGDA patterning. Thicknesses extracted from resonance measurements showed good agreement with measurements using an optical microscope. In addition, PEGDA microcantilevers with various dimensions and thicknesses were fabricated on glass and silicon substrates. Surfaces of fabricated all hydrogel microcantilevers were flat enough to facilitate other post processing and to be used for various sensing applications.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.3
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• pp.151-160
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• 2007

We report the label-free biomolecules detection based on nanomechanical micro cantilevers operated in dynamic mode for detection of two marker proteins (myoglobin and creatin kinase-MB (CK-MB)) of acute myocardical infarctions. When the specific binding between the antigen and its antibody occurred on the fuctionalized microcantilever surface, mechanical response (i.e. resonant frequency) of microcantilevers was changed in lower frequency range. We performed the label-free biomolecules detection of myoglobin and CK-MB antigen in the low concentration (clinical threshold concentration range) as much as 1 ng/ml from measuring the dynamic response change of micro cantilevers caused by the intermolecular force. Moreover, we estimate the surface stress on the dynamic microcantilevers generated by specific antibody-antigen binding. It is suggested that our dynamic microcantilevers may enable one to use the sensitive label-free biomolecules detection for application to the disease diagnosis system based on mechanical immuno-sensor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.34-38
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• 2005

This is a widespread requirement for low cost lightweight thermal imaging sensors for both military and civilian applications. Today, a large number of uncooled infrared detector developments are under progress due to the availability of silicon technology that enables realization of low cost IR sensor. System prices are continuing to drop, and swelling production volume will soon drive process substantially lower. The feasibility of micromechanical optical and infrared (IR) detection using microcantilevers is demonstrated. Microcantilevers provide a simple Structurefor developing single- and multi-element sensors for visible and infrared radiation that are smaller, more sensitive and lower in cost than quantum or thermal detectors. Microcantilevers coated with a heat absorbing layer undergo bending due to the differential stress originating from the bimetallic effect. This paper reports a micromachined silicon uncooled thermal imager intended for applications in automated process control. This paper presents the design, fabrication, and the behavior of cantilever for thermomechanical sensing.

• Journal of Sensor Science and Technology
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• v.21 no.3
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• pp.186-191
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• 2012

In this paper, we present a pH measurement method that uses a microcantilever-array-based biosensor system. It is composed of microcantilever array, liquid cell, micro syringe pump, laser diode array, position sensitive detector, data acquisition device, and data processing software. Four microcantilevers are functionalized with pH-sensitive MHA(mercaptohexadecanoic acid) as a probe, while three microcantilevers are functionalized with HDT(hexadecane thiol) as reference. We prepare PBS(phosphate buffered saline) solutions of different pH and inject them into the liquid cell with a predefined volumetric speed at regular time intervals. The functionalized mircocantilevers in the liquid cell deflect as a self-assembled monolayer on the microcantilever binds with probe molecules in the solution. The difference in deflection between the MHA-covered probe microcantilever and the HDT-covered reference microcantilever was used to compensate for thermal drift. The deflection difference clearly increases with increasing pH in the solution. It was shown that when the pH values of the PBS solutions are high, there were large variations in the deflection of microcantilevers, whereas there were small variations for low pH value. The experimental results show that the microcantilever array functionalized with MHA and HDT can detect pH value with good repeatability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.606-611
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• 2007

Proper orthogonal decomposition (POD) is a method for extracting bases for modal decomposition from the ensemble of dynamic signals. Using the POD method, we analyzed the proper orthogonal modes (POMs) of AFM microcantilevers in dynamic mode operations such as Tapping Mode. The POMs and POVs (proper orthogonal values) were computed through MATLAB simulation for the 5-mode model of the microcantilever. We found that the POV portion of the higher POMs of the tapping microcanilever slightly increased in comparison with no tapping. This implies that the modal energy in the fundamental mode can be transferred to the higher modes during tapping.

• Journal of Sensor Science and Technology
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• v.20 no.1
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• pp.40-45
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• 2011

Microcantilevers have been actively used in probe-based microscopy and gravimetric sensing for biological or chemical analytes. To integrate actuation or detection schemes in the structure, typical fabrication processes include several photolithographic steps along with conventional MEMS fabrication. In this paper, a simple and straightforward way to fabricate and operate silicon microcantilever mass sensors is presented. The fabricated microcantilever sensors which can be electrostatically actuated require only two photolithographic steps. Resonant characteristics of fabricated microcantilevers are measured with a custom optical-lever and results show size-dependent quality factors. Using a $40\;{\mu}m$ long, $7\;{\mu}m$ wide, and $3\;{\mu}m$ thick cantilever, we achieved subfemtogram mass resolution in a 1 Hz bandwidth.

• Coupled systems mechanics
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• v.4 no.3
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• pp.251-262
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• 2015

The current paper aims at investigating the nonlinear dynamical behaviour of an electrically actuated microcantilever. The microcantilever is excited by a combination of AC and DC voltages. The nonlinear equation of motion of the microcantilever is obtained by means of force and moment balances. A high-dimensional Galerkin scheme is then applied to reduce the equation of motion to a discrete model. A numerical technique, based on the pseudo-arclength continuation method, is used to solve the discretized model. The electrostatic deflection of the microcantilever and static pull-in instabilities, due to the DC voltage, are analyzed by plotting the so-called DC voltage-deflection curves. At the simultaneous presence of the DC and AC voltages, the nonlinear dynamical behaviour of the microcantilever is analyzed by plotting frequency-response and force-response curves.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.11-15
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• 2006

We propose an optical and an electrical detection methods for detecting various bio-molecules effectively with microcantilevers. The microcantilevers were fabricated employing surface micromachining technique that has attractive advantages in terms of cost efficiency, simplicity and ability of fabricating in array. The fluid cell system for injection of bio-molecular solution is fabricated using polydimethylsiloxane (PDMS) and a fused silica glass. The microcantilever is deflected with respect to the difference of the surface stress caused by the formation of self-assembled bio-molecules on the gold coated side of the microcantilever. It detected cystamine dihydrochloride and glutaraldehyde molecules and analyzed individual concentrations of the cystamine dihydrochloride solution. We confirm that the deflections of bending-up or bending-down are occurred by the bio-molecule adsorption and microcantilever can be widely used to a ${\mu}-TAS$ and a lab-on-a-chip for a potential detection of various bio-molecules.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.125-128
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• 2004

AFM(Atomic Force Microscope) becomes a versatile tool in the nanoscale measurements and processes. Especially the tapping mode is a very useful mode in AFM operation to measure and process at the nanoscale. Although the tapping mode has a great potential for the novel techniques such as phase imaging, however, it is not clearly known the fundamental mechanics affected by complex tip-sample interactions. This paper shows the various nonlinear dynamic features in tapping mode AFM microcantilevers including hysteretic jumps and period doublings of the microcantilevers. Also it is discussed the complex dynamics of CNT(Carbon Nanotube) probes and the opportunities on the nanoscale nonlinear dynamics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.85-87
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• 2014