Eniko T Enikov

Abstract:

This paper is focused on the design of metal (Ni) electro-thermal micro-actuators, fabricated via a single electro-plating step. Analytical and finite-element solutions of the electro-thermal and thermo-elastic problems are presented to aid in the design of the devices. A separate section is devoted to the problem of displacement determination using charge sensitive amplifiers for high-precision capacitance measurements. Finally, a possible future use of these actuators in impedance-based biosensors is outlined. copyright The Electrochemical Society.

Abstract:

Without control, the desired motions of machines do not occur, and the desired equilibria and stationary motions are often unstable. Human operator or computer control may be needed to control and stabilize these machines. An important common feature of both analog and digital controllers is the time delay that is introduced into the system. Even when these delayed systems should be stable, the experiments show small stochastic oscillations around the desired motion, as are often experienced in robotics. In case of the stabilization of an inverted pendulum, the analysis of the equation of motion shows that chaotic vibrations occur around the equilibrium even when stochastic effects related to human control are not present. In advanced design work of digitally controlled machines, it is vital to know the characteristics of this chaotic behavior. The estimation of the distribution of vibration amplitudes and the frequency range should be available at the design stage. This initiates the analysis of the so-called microchaos or μ-chaos.

Abstract:

This article introduces an optical device for measuring and recording the vibrations during milling. The constructed apparatus is able to discriminate between stable cutting and chatter vibration. A review of various chatter detection methods is presented. It lists basic numerical approximation methods to predict chatter and the devices used to detect unstable cutting. A discussion on the importance of experimental detection versus theoretical predictions is also included. The article further presents the measurement setup, its basic components, and their parameters along with the basic principles of the measurements and the theoretical framework of the stability analysis. The theoretical framework is then applied to show the chatter determining frequencies and to determine what has to be detected during the measurements. Experimental results for slotting and down milling with different immersion ratios are also presented. These include stability maps based on the power spectrum density (PSD) graphs of the collected data and confirmed by photographs of the cut surfaces. The conclusion summarizes the results, and describes advantages and disadvantages of the setup. © Taylor & Francis Group, LLC.

Abstract:

This paper presents a novel concept for integrating a magnetic microparticle sandwich assay onto a microcantilever beam, towards rapid and sensitive detection of E. Coli. The gold coated surface of the microcantilever beam and the surface of superparamagnetic microparticles are functionalized with anti-E. coli IgG so that they bind only in presence of and via the E. coli. An external magnetic field produced by an electromagnet is used to enhance the microcantilever deflection, and an optical lever method is used to sensitively detect it. © 2009 IEEE.

Abstract:

The development of new tonometers requires laboratory tests on enucleated eyes where the intraocular pressure (IOP) is usually controlled by the use of a fluid column (manometry). This article describes a novel eye pressure regulation system for IOP tests along with a new concept of mechanical palpation tonometry. Manometry is commonly regarded as an invasive technique that can measure precisely the pressure inside the eye. It is a common laboratory technique for evaluating changes in IOP over time, and for providing reference pressure by which all other tonometers can be evaluated. In general, the system consists of a fluid column (1 % saline solution) connected via PVC tubing to a three way valve. The valve is able to connect the column branch to a syringe with a 21G needle inserted into the vitreous humor and to a pressure transducer. The syringe needle is inserted in the eye through the side, with the tip located approximately in the middle of the vitreous chamber [1]. However, this method is prone to errors due to the gelatinous and highly fibrous nature of the vitreous matter that could easily clog the syringe needle and prevent the accurate pressure control and measurement. To resolve this difficulty, we report an alternative control of the IOP through the anterior chamber of the eye. In addition to the clogging, severed blood vessels in enucleated eyes result in large rate of leakage of intraocular fluid. With these modifications in place, it was demonstrated that the pressure sensing is fast and accurate, allowing investigation of mechanical trans-scleral palpation and the development of a new concept of mechanical palpation tonometry device. The device is based on multiple probes for measuring contact forces. Experimental data from the performance of the device are presented. Copyright © 2011 by ASME.