Design and implementation of low leakage MEMS microvalves

Yıldırım, Ender
This thesis presents analysis, design, implementation, and testing of electrostatically actuated MEMS microvalves. The microvalves are specifically designed for lab-on-a-chip applications to achieve leakage ratios below 0.1 at pressure levels in the order of 101 kPa. For this purpose, two different microvalves are presented in the study. In the proposed designs, electrostatic actuation scheme is utilized to operate the microvalves in normally open and normally closed modes. Characterization of normally open microvalves show that, microvalves with radii ranging between 250 m and 450 m can be operated by applying voltages between 40 and 100 V with air and oil. It is also shown that the actuation potential becomes minimum for working fluids with dielectric constant around 3-5. During the tests, it could not be possible to operate normally open electrostatic microvalves with DI water, due to its high dielectric constant and conductivity. During flow tests with air, 17 % leakage is observed under 10 kPa inlet pressure, when actuated by applying 85 V. On the other hand, it is shown that this leakage can be controlled precisely by tuning the actuation potential with sensitivity of 10-3 V-1. To solve the problems observed in normally open microvalve, a normally closed electrostatic microvalve design is proposed. The design isolates the working fluid from electric field, hence makes it possible to operate the microvalve with any working fluid. Moreover, unique and reconfigurable valve seat design enables low leakage. Pull-in tests are carried out with air and DI water under no-flow condition. During the tests, 46-66 V pull-in voltage is observed, independent of the working fluid. Besides, during flow tests with DI water, no leakage is detected up to 20 kPa inlet pressure. Considering actuation and leakage properties of these microvalves, a multi-drug effect analysis system is proposed. The system utilizes normally closed microvalves to generate micro-droplets of different drug with cells entrapped inside. Prototypes of the system are fabricated and tested with 3 m diameter polystyrene micro-beads. The tests show that it can be possible to entrap single bead in 135 pl volume droplets. The prototypes are also tested with living yeast cells. It could also be possible to entrap yeast cells in micro-droplets using the proposed system. As an extension to the multi-drug effect analysis system, a microvalve controlled droplet metering technique is proposed. The technique uses normally open microvalves to control the flow rate of the carrier fluid in a droplet based system. Initial tests show that it can be possible to generate pl size micro-droplets with 6 % precision. During the tests, voltage sensitivity of the technique is measured as 0.4 pl/V.


Design and prototyping of an electromagnetic mems energy harvester for low frequency vibrations
Türkyılmaz, Serol; Külah, Haluk; Department of Electrical and Electronics Engineering (2011)
This thesis study presents the design, simulation, and fabrication of a low frequency electromagnetic micro power generator. This power generator can effectively harvest energy from low frequency external vibrations (1-100 Hz). The main objective of the study is to increase the efficiency of the previously proposed structure in METU-MEMS Center, which uses the frequency up-conversion technique to harvest energy from low frequency vibration. The proposed structure has been demonstrated by constructing severa...
Design and implementation of perforation on high fill factor structures for uncooled infrared sensors
Çetin, Ramazan; Akın, Tayfun; Department of Electrical and Electronics Engineering (2016)
This thesis presents the design and implementation of the perforation on high fill factor structures; e.g., umbrella structures, for uncooled infrared detectors. The study is mostly focused on the effect of the perforation on the absorption performance of the sensor pixels. The introduction of the perforation to the umbrella structure is expected to improve the absorption performance which can be degraded due to a trending issue nowadays, the pixel size reduction. In literature, perforation is also proposed...
Simulation of Drop-Weight Impact Test on Composite Laminates using Finite Element Method
Bozkurt, Mirac Onur; Parnas, Kemal Levend; Çöker, Demirkan (Elsevier, 2019-01-01)
This study presents the simulation of standard drop-weight impact test on a [0/90/0]s composite laminate. For this purpose, a three-dimensional virtual test setup is developed in ABAQUS/Explicit finite element tool. Hemispherical impactor and specimen fixture are modeled as rigid bodies. Composite plate is modeled as a 3-D deformable solid and discretized using a biased mesh for computational efficiency. For simulation of ply damage in the composite laminate, a continuum damage mechanics based damage model ...
Design of an X-band 3-bit RF MEMS constant phase shifter
Kuzubaşlı, Ahmet; Akın, Tayfun; Demir, Şimşek; Department of Electrical and Electronics Engineering (2016)
This thesis presents a 3-bit 180° constant phase shifter design implementing Co-Planar Waveguide (CPW) and RF MEMS variable capacitors with ±1.8% accuracy at 10 GHz and ±5.8% maximum peak error between 9-11 GHz. The phase shifter with minimum phase errors is determined by considering exemplary circuit simulations of different phase shifter types designed with a novel in-house RF MEMS fabrication process [1] parameters. Due to its wide-band characteristics and CPW compatibility, the selected topology is the ...
A MEMS based drug effect analysis system utilizing droplet microfluidics
Özkan, Metin Dündar; Külah, Haluk; Yıldırım, Ender; Department of Electrical and Electronics Engineering (2018)
This thesis proposes a fully integrated lab-on-a-chip system designed for drug effect analysis based on the droplet microfluidics. It is mainly designed for screening multi-drug responses of cells in an automated operation. The distinguished feature of the drug screening system is that it includes droplet-based single cell encapsulation. The system includes two main subsystems which are parylene-based and normally closed electrostatic microvalves and droplet generation system. The integration of microvalves...
Citation Formats
E. Yıldırım, “Design and implementation of low leakage MEMS microvalves,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.