• 센서학회지
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• 제21권3호
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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.

• 센서학회지
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• 제20권1호
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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.

• 비파괴검사학회지
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• 제31권5호
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• pp.487-493
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• 2011

비표지 방식의 압전 마이크로캔틸레버 질량센서를 이용하여 간세포암의 혈청표지물질인 알파태아단백(alpha fetoprotein, AFP)을 정상 농도인 10 ng/ml까지 정량적으로 검출하였다. 압전 마이크로캔틸레버 질량센서는 캔틸레버의 질량변화에 의하여 센서의 공진주파수가 변화되는 원리를 이용하여 센서에 붙은 물질의 질량을 측정하며, 센서의 공진주파수는 컨덕턴스 스펙트럼을 이용하여 전기적으로 측정한다. 제작된 센서는 공진 주파수가 약 1.34 MHz, 질량 민감도가 약 175 Hz/pg이며 단백질이 붙을 때 캔틸레버의 표면 스트레스 변화에 대한 센서의 공진 주파수 변화를 줄일 수 있도록 설계되어 질량센서로써 신뢰도를 높였다. 'Dip and dry' 방법으로 캔틸레버의 프로브 영역을 시약과 반응시켜서 AFP 항체를 고정화하고 AFP 항원을 검출하는 실험을 수행하였다. 10 ng/ml과 50 ng/ml농도의 항원에서 10분간 항원-항체 면역반응을 시켰을 때 센서에 검출된 항원의 질량이 각각 6.02 pg과 10.67 pg이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1767-1772
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• 2008

A microcantilever is a well-known MEMS structure for sensing bio-chemical molecules. When bio-chemical molecules are adsorbed on the microcantilever's surface, resonance frequency shift is generated. There are two issues in this phenomena. The first one is which one between mass change and surface stress change effects is more dominant on the resonance frequency shift. The second one is what will be the performance change when the boundary condition is changed from cantilevers to double clamped beams. We have studied the effect of surface stress change and compared it with that of mass change by using FEM analysis. Furthermore, for microstructures having different boundary conditions, we have studied Q-factor, which determines the detection limit of micro/nano mechanical sensors.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권3호
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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.

• 한국진공학회지
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• 제16권1호
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• pp.52-57
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• 2007

생명현상 발현에 중요한 역할을 하는 생체 분자간 특이적 상호작용을 단분자 수준에서 이해하려는 연구는 매우 중요한 일이다. 나노 바이오 측정기술을 이용하여 여러 복잡한 생명현상을 그 기본 단위인 단일 세포 차원에서 직접 측정하여 응용하려는 시도가 이루어지고 있다. 이런 시도로써, 원자힘 현미경을 이용한 생체분자간의 결합력 측정은 생명현상과 가장 유사한 환경에서 단일 생체 분자간 또는 분자 내 힘을 직접 측정함으로써, 단일 생체분자의 현상을 관찰 할 수 있다는 장점을 가지고 있다. 특히 단분자 힘 분광학을 이용한 단일 생체분자내의 세부 단위체간 상호작용에 대한 연구와 단백질-단백질, 단백질-리간드, DNA-DNA의 분자인지 상호작용에 대한 연구는 많은 생명과학 분야 연구자들의 관심을 끌고 있을 뿐만 아니라 더 나아가 새로운 관련 기술의 개발을 촉진시키고 있다.