Papers by Author: Levent Trabzon

Abstract: In this paper we present fabrication steps for manufacturing MEMS based magnetometer which is actuated by Lorentz force in the middle point of beam which has been fixed from both two edges (Clamped - Clamped). We utilized two different process sequences in order to fabricate microsystems properly. The structures were first fabricated on bulk Si-wafer and the fabrication of these sensors was characterized by built in stress in the beam and etching methods in the processes. The second approach was performed on SOI Si-wafer. Two fabrication routes are compared in terms of working MEMS structures. The microstructures are manufactured successfully by a process sequence based on SOI-Si wafer.

Abstract: Monitoring body fluids such as sweat composition can provide useful information about the physiological status. Physiological monitoring of body fluids such as sweat with a textile-based system has the advantage of being non-invasive and easily accessible and such monitoring is beneficial to indicate information about body's physiological status. In the present study, it is aimed to design a textile-based system with non-invasive methods which can be used to monitor a sportsman's performance. A novel, disposable and wearable biochemical analytical device was designed and fabricated by patterning micro channels and reservoirs using SU-8 photoresist through photolithography technique on an absorbant bicomponent Evolon® nonwoven substrate. It was obtained that hydrophilic reservoirs were well defined and demarcated by hydrophobic barriers. Therefore, no liquid leakage was observed around the reservoirs which was crucial for achieving a proper enzyme immobilization and the successful detection of the color change after the simulated sweat was deposited on the hydrophilic reservoir areas. Analyte optimization studies revealed that color change became more evident with the increasing analyte concentration until 20 mM and started to decrease with further increase due to analyte inhibition. Also, on textile fabrics, color densities started to decrease after 40 mM analyte concentration.

Abstract: A novel textile-based analytical device with a simultaneous, rapid, sensitive and qualitative response for analyte detection that may have a potential use in different body fluids such as sweat, blood, saliva and urine is proposed in this study as an alternative to its paper-based counterparts. A porous polypropylene spunbond nonwoven was used as base fabric which is superior to paper with higher tear and crinkle resistance, flexibility and wearability.

Abstract: High force amplification in micro-scale can be achieved by MEMS compliant systems and such systems have been recently preferred to obtain high output forces in micro actuators due to its monolithic structure and ease of fabrication. We studied the mechanism of novel MEMS force amplifier in dynamic mode by modeling its rigid body mechanism with Matlab/Simulink programming. Kinematic analysis and dynamic response of the MEMS compliant system was obtained by modeling of velocity and acceleration parameters, and ramp input function, respectively. We found that the output force goes to infinity at zero-crank angle and there is 2650 times force amplification by a given very small crank rotation about 2.30.

Abstract: We fabricated Si Nano-columns by a femtosecond laser with various wavelengths and process parameters, whilst the specimen was submerged in water. The experiments were carried out by three types of wavelengths i.e. 1030 nm, 515nm, 343nm, with 500 fs laser pulses. The scales of these spikes are much smaller than micro spikes that are constructed by laser irradiation of silicon surface in vacuum or gases like SF6, Cl2. The Si nano-columns of 300 nm or less in width were characterized by SEM measurements. The formation of these Si Nano-columns that were revealed by SEM observation, indicates chemical etching with laser ablation occurred when surface exposed by laser beam. We observed 200 nm spikes height at the center of laser beam profile and the ones uniform in height at lateral incident area.

Abstract: We studied the effect of geometry on single focusing of particles in the passive microfluidic channels. There is a quantitative analysis of focusing on non-axisymmetric straight channels with two different unique designs as well as curved channels having symmetrical and asymmetrical radius of curvatures in one turn. We found that there is a clear relationship in existence of single line focusing with the degree of non-symmetry in microchannels. One-degree of asymmetry in straight channels does not induce any formation of single focusing, but single line focusing is pronounced by two-degree of asymmetry in straight channels. On the other hand, single line focusing in the curved channels is enhanced with asymmetrical radius of curvatures in one turn. The single line focusing in curved channels is seen at Rep values higher than 1, which gives us better continuous and high-throughput performance. The position of single focused particles in the microchannels is found to be 50 m with respect to the channel wall in the asymmetrical curved microchannels.