Browsing by Subject "Cantilever"

Now showing 1 - 6 of 6

Open Access
Enhanced higher-harmonic imaging in tapping-mode atomic force microscopy
(AIP, 2005) Balantekin, M.; Atalar, Abdullah
Higher-harmonics generation in a tapping-mode atomic force microscope is a consequence of the nonlinear tip-sample interaction force. The higher harmonics contain important information about the materials’ nanomechanical properties. These harmonics can be significantly enhanced by driving the cantilever close to a submultiple of its resonant frequency. We present the results of enhanced higher-harmonic imaging experiments on several samples. The results indicate that enhanced higher harmonics can be utilized effectively for both material characterization and surface roughness analysis with a high signal-to-noise ratio. © 2005 American Institute of Physics
Open Access
Fabrication and characterization of microelectromechanical resonators
(2006) Özer, Sevil
Micromachined mechanical resonators are of considerable interest because of their many important scienti c and technological applications. They can be used as a components of radio-frequency lters in communication systems, mechanical electrometer or magnetometer for sensitive detection of force, charge, pressure. This work is directed towards the fabrication and characterization of microelectromechanical resonators, cantilevers and bridges. The SOI cantilever and the silicon nitride cantilevers and bridges are fabricated by using surface micromachining techniques. They are fabricated in the Advanced Research Laboratory of Bilkent University. The center frequencies are ranging from 20 kHz to 270 kHz. The characterization of cantilevers and bridges are done by using the beam de ection method and the ber optic interferometer method. The dynamic response of the rst devices, such as the resonance frequencies and the quality factors will be reported. In addition, simple beam theory and some fundamental loss mechanisms will be discussed. The experimental results will also be compared with the theoretical ones.
Open Access
Grating loaded integrated optical cantilevers
(2010) Karademir, Ertuğrul
Cantilever beams are the most important parts of standard scanning probe microscopy. In this work, an integrated optical approach to sense the deflection of a cantilever beam is suggested and realized. A grating coupler loaded on the upper surface of the cantilever beam couples the incident light to the chip, which is then conveyed through a taper structure to a waveguide to be detected by a photodiode. Deflections of the cantilever beam change the optical path and hence the total transmitted intensity. Finally an optical signal is produced and this signal is measured. Resonance peak of 27.2 Q factor is obtained, which could be further enhanced by proper vibration isolation and employment of vacuum environment.
Open Access
High-resolution imaging of elastic properties using harmonic cantilevers
(Elsevier, 2004) Sahin, O.; Yaralioglu, G.; Grow, R.; Zappe, S. F.; Atalar, Abdullah; Quate, C.; Solgaard, O.
We present a micromachined scanning probe cantilever, in which a specific higher-order flexural mode is designed to be resonant at an exact integer multiple of the fundamental resonance frequency. We have fabricated such cantilevers by reducing the stiffness of the third order flexural mode relative to the fundamental mode, and we have demonstrated that these cantilevers enable sensing of non-linear mechanical interactions between the atomically sharp tip at the free end of the cantilever and a surface with unknown mechanical properties in tapping-mode atomic force microscopy. Images of surfaces with large topographical variations show that for such samples harmonic imaging has better resolution than standard tapping-mode imaging.
Open Access
Investigation of lateral forces in dynamic mode using combined AFM/STM
(2007) Atabak, Mehrdad
In this Ph.D. work, we constructed a ¯ber optic interferometer based non-contact Atomic Force Microscope (nc-AFM) combined with Scanning Tunneling Micro- scope(STM) to study lateral force interactions on Si(111)-(77) surface. The in- terferometer has been built in such a way that its sensitivity surpasses that of the earlier versions used in normal force measurements. The improvement in the resolution of the interferometer has allowed us to use sub-Angstrom oscillation amplitudes to obtain quantitative lateral force measurements. We have observed single and double atomic steps on Si(111)-(77) surface in topography and lat- eral sti®ness images. This information allowed us to measure the lateral forces directly and quantitatively. We have also carried out lateral force-distance spec- troscopy experiments, in which we simultaneously measured the force gradient and tunneling current, as the sample is approached towards the tip. The lateral force?distance curves exhibit a sharp increase of the force gradient, just after the tunnel current starts to increase, while the sample is approaching to the tip. We observed only positive force gradients. In separate experiments, we imaged the Cu-TBPP molecules deposited on Cu(100) surface in normal and torsional mode in dynamic force microscope us- ing STM feedback, with a homemade tungsten cantilever. Our experiments have shown the possibility of manipulating molecules on surface using a vibrating can- tilever. However the forces involved in these experiments are not quantitatively measured due to limitations of the method.
Open Access
Microcantilever based disposable viscosity sensor for serum and blood plasma measurements
(2013) Cakmak O.; Elbuken, C.; Ermek, E.; Mostafazadeh, A.; Baris I.; Erdem Alaca, B.; Kavakli I.H.; Urey H.
This paper proposes a novel method for measuring blood plasma and serum viscosity with a microcantilever-based MEMS sensor. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. Real-time monitoring of cantilever resonant frequency is performed remotely using diffraction gratings fabricated at the tip of the dynamic cantilevers. Only few nanometer cantilever deflection is sufficient due to interferometric sensitivity of the readout. The resonant frequency of the cantilever is tracked with a phase lock loop (PLL) control circuit. The viscosities of liquid samples are obtained through the measurement of the cantilever's frequency change with respect to a reference measurement taken within a liquid of known viscosity. We performed measurements with glycerol solutions at different temperatures and validated the repeatability of the system by comparing with a reference commercial viscometer. Experimental results are compared with the theoretical predictions based on Sader's theory and agreed reasonably well. Afterwards viscosities of different Fetal Bovine Serum and Bovine Serum Albumin mixtures are measured both at 23. °C and 37. °C, body temperature. Finally the viscosities of human blood plasma samples taken from healthy donors are measured. The proposed method is capable of measuring viscosities from 0.86. cP to 3.02. cP, which covers human blood plasma viscosity range, with a resolution better than 0.04. cP. The sample volume requirement is less than 150. μl and can be reduced significantly with optimized cartridge design. Both the actuation and sensing are carried out remotely, which allows for disposable sensor cartridges. © 2013 .