Source: https://profiles.arizona.edu/person/enikov
Timestamp: 2019-04-19 08:17:19+00:00

Document:
Enikov, E. T., Edes, G., & Anton, R. (2017). THERMAL DRIFT AND DYNAMIC RESPONSE OF MICRO FLOW SENSORS FOR SMART VP SHUNTS. PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2016, VOL. 3 .
Enikov, E. T., Habib, G., Miklos, A., Stepan, G., & Rega, G. (2017). Nonlinear model-based parameter estimation and stability analysis of an aero-pendulum subject to digital delayed control. International Journal of Dynamics and Control , 5(3), 629-643.
Kyselica, R., & Enikov, E. T. (2017). DYNAMIC FOCUSING OF ELECTROSPINNING PROCESS WITH QUADRUPOLE TRAPS. PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2016, VOL. 4A .
McCafferty, S., Levine, J., Schwiegerling, J., & Enikov, E. T. (2017). Goldmann applanation tonometry error relative to true intracameral intraocular pressure in vitro and in vivo. BMC OPHTHALMOLOGY , 17.
Szabo, Z., & Enikov, E. T. (2017). DEVELOPMENT OF HAPTIC COMMUNICATION DEVICE FOR DISABLED PERSONS. PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2016, VOL. 14 .
Szabo, Z., Enikov, E. T., & Kyselica, R. (2017). NANOFACTURE: SENIOR DESIGN EXPERIENCE IN NANOTECHNOLOGY. PROCEEDINGS OF THE ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2016, VOL. 5 .
McCafferty, S., Lim, G., Duncan, W., Enikov, E., & Schwiegerling, J. (2016). Goldmann Tonometer Prism with an Optimized Error Correcting Applanation Surface. TRANSLATIONAL VISION SCIENCE & TECHNOLOGY , 5(5).
Enikov, E., Enikov, E. T., Polyvás, P. P., & Peyman, G. (2013). Trans-scleral tactile tonometry: an instrumented approach. Medical engineering & physics , 35(7).
This article describes a feasibility study of a novel trans-scleral tonometer based on the use of an instrumented form of digital palpation tonometry. Similar to manual digital palpation tonometery, trans-scleral tonometer utilizes two force probes offset by a fixed distance. Force indentation data from these probes have been shown to correlate with the intraocular pressure (IOP) of the eye. Enucleated porcine eyes were used to experimentally validate the approach. The observed hysteresis in the force data was analyzed using an analytical model that accounts for the outflow of the aqueous humor. The predictions of the model indicate that the primary reason behind the observed hysteresis is stress relaxation (accommodation) in the visco-elastic corneo-scleral shell. Experimental data from eye distention and indentation tests were then used to infer the conditions under which the novel tonometer would be expected to have an accuracy of ±1 mmHg. Analysis of the data shows that indentation rates should be kept below 0.5 mm/s for a pressure range of 10-35 mmHg. Two commonly used pressure control protocols were tested in an effort to ensure accurate IOP values during the palpation tests. Due to the large increase of IOP during digital palpation, the trans-scleral (intra-vitreous) pressurization was found to be inadequate, leading to clogging of the line by the displaced vitreous. No such problems were identified when the eye was pressurized through the cornea and into the anterior chamber. Force data from multiple palpation experiments are used to generate calibration curves for a two-probe conceptual tonometer. The calibration showed that a 10 mN of force variation corresponds to 1 mmHg of IOP change. A possible implementation using a contoured facial mask is also presented.
Polyvás, P. P., Peyman, G., & Enikov, E. T. (2013). Trans-scleral tactile tonometry: An instrumented approach. Medical Engineering and Physics , 35(7), 937-943.
PMID: 23007038;Abstract: This article describes a feasibility study of a novel trans-scleral tonometer based on the use of an instrumented form of digital palpation tonometry. Similar to manual digital palpation tonometery, trans-scleral tonometer utilizes two force probes offset by a fixed distance. Force indentation data from these probes have been shown to correlate with the intraocular pressure (IOP) of the eye. Enucleated porcine eyes were used to experimentally validate the approach. The observed hysteresis in the force data was analyzed using an analytical model that accounts for the outflow of the aqueous humor. The predictions of the model indicate that the primary reason behind the observed hysteresis is stress relaxation (accommodation) in the visco-elastic corneo-scleral shell. Experimental data from eye distention and indentation tests were then used to infer the conditions under which the novel tonometer would be expected to have an accuracy of ±1 mmHg. Analysis of the data shows that indentation rates should be kept below 0.5 mm/s for a pressure range of 10-35 mmHg. Two commonly used pressure control protocols were tested in an effort to ensure accurate IOP values during the palpation tests. Due to the large increase of IOP during digital palpation, the trans-scleral (intra-vitreous) pressurization was found to be inadequate, leading to clogging of the line by the displaced vitreous. No such problems were identified when the eye was pressurized through the cornea and into the anterior chamber. Force data from multiple palpation experiments are used to generate calibration curves for a two-probe conceptual tonometer. The calibration showed that a 10 mN of force variation corresponds to 1 mmHg of IOP change. A possible implementation using a contoured facial mask is also presented. © 2012 IPEM.
Polyvás, P., Madarász, M., & Enikov, E. T. (2013). Development of Tactile Eye Stiffness Sensor. Experimental Mechanics , 53(5), 819-828.
Abstract: This article describes the design of a novel trans-scleral tonometer based on the use of multiple force sensors forming a mechanical stiffness sensor. The approach is akin to an instrumented form of digital palpation tonometry in which manual paplation is used to infer the stiffness, and hence, the intraocular pressure of the eye. Force indentation data from multiple probes has been shown to correlate with the intraocular pressure (IOP) using encucleated porcine eyes. A noticeable amount of hysteresis has been observed during indentations at higher rate. Analysis of the experimental data indicates that stress relaxation (accommodation) in the visco-elastic corneo-scleral shell is the primary factor of the observed hysteresis. Further tests under different indentation rates show that the novel tonometer is expected to have an accuracy of ±1 mmHg when the indentation rate is kept below 0.5 mm/sec for pressure range of 10-35 mmHg. Using a calibrated finite element model of the measurement, the effect of lateral and angular misalignment is also examined. The results show that the position and orientation of the tactile sensor has to be controlled to within ±1 mm and ±3° in order to achieve a target accuracy of ±1 mmHg. © 2012 Society for Experimental Mechanics.
Enikov, E. T., & Campa, G. (2012). Mechatronic Aeropendulum: Demonstration of Linear and Nonlinear Feedback Control Principles With MATLAB/Simulink Real-Time Windows Target. IEEE TRANSACTIONS ON EDUCATION , 55(4), 538-545.
Enikov, E. T., & Campa, G. (2012). USB-powered portable experiment for classical control with MATLAB Real-Time Windows Target. ASEE Annual Conference and Exposition, Conference Proceedings .
Abstract: Engineering education has the objective of not only presenting the scientific principles, i.e., engineering science, but also of teaching students how to apply these to real problems. Therefore, hands-on laboratories have been an integral part of the engineering curriculum since its inception. This presentation will demonstrate the use of a novel low-cost experimental apparatus for use in a typical undergraduate course in control systems taught to mechanical engineering students, i.e. students with limited exposure to electrical engineering. The system demonstrates the use of MATLAB tools such as Simulink Real Time Windows Target and Control Systems toolboxes to illustrate all stages of design of a closed-loop control systems including: system modeling, parameter identification, analysis of stability of a closed-loop system, design of dynamic compensator in the continuous space and implementation of an equivalent digital controller using the Simulink Real Time Windows Target environment. The hardware apparatus consists of a DC micro-motor attached to a carbon fiber rod. The angular displacement is measured with an analog potentiometer, which acts as the pivot point for the carbon fiber rod. The DC micro-motor is powered by a low cost, custom circuit board, which is USB-powered requiring no external power adaptor or extra cabling. Attached to the micro-motor is a small propeller which provides thrust force needed to rotate the pendulum to a desired angle. The experiment is designed to operate from student's laptops, therefore no special laboratory space is required. The project was tested in a classical control systems design class offered to senior-level mechanical engineering students. Student feedback and survey data on the effectiveness of the module are presented along with examples of student assignments illustrating the use of hardware. © 2012 American Society for Engineering Education.
Enikov, E. T., & Eke, E. (2012). Teaching classical control system course with portable student-owned mechatronic kits. ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) , 5, 509-516.
Abstract: Teaching classical controls systems design to mechanical engineering students presents unique challenges. While most mechanical engineering programs prepare students to be wellversed in the application of physical principles and modeling aspects of physical systems, implementation of closed loop control and system-level analysis is lagging. It is not uncommon that students report difficulty in conceptualizing even common controls systems terms such as steady-state error and disturbance rejection. Typically, most courses focus on the theoretical analysis and modeling, but students are left asking the questions... How do I implement a phase-lead compensator? ...What is a non-minimum phase system? This paper presents an innovative approach in teaching control systems design course based on the use of a low-cost apparatus that has the ability to directly communicate with MATLAB and its Simulink toolbox, allowing students to drag-and-drop controllers and immediately test their effect on the response of the physical plant. The setup consists of a DC micro-motor driving a propeller attached to a carbon-fiber rod. The angular displacement of the rod is measured with an analog potentiometer, which acts as the pivot point for the carbon fiber rod. The miniature circuit board is powered by the USB port of a laptop and communicates to the host computer using the a virtual COM port. MATLAB/Simulink communicates to the board using its serial port read/write blocks to command the motor and detect the deflection angle. This presentation describes a typical semester-long experimental protocol facilitated by the low-cost kit. The kit allows demonstration of classical PID, phase lead and lag controllers, as well as non-linear feedback linearization techniques. Comparison between student gains before and after the introduction of the mechatronic kits are also provided. Copyright © 2012 by ASME.
Enikov, E. T., & Ganji, M. (2012). Numerical simulation and stability analysis of thin flexible micro film for thermotunneling application. ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) , 4(PARTS A AND B), 407-413.
Abstract: Combined thermionic emission and tunneling of hot elec- Trons (thermo-tunneling) has emerged as a potential new solid- state cooling technology. Practical implementation of thermo- Tunneling, however, requires the formation of a nanometer-sized gap spanning macroscopically significant surfaces. Thermo- Tunneling is a term used to describe combined emission of hot electrons (thermionic emission) and tunneling of electrons through a narrow potential barrier between two surfaces (field emission). Thermo-tunneling of hot electrons across a few- nanometer gap has application to vacuum electronics, flat panel displays, and holds great potential in thermo-electric cooling and energy generation. Development of new thermo-tunneling applications requires creation of a stable nanometer gap be- Tween two surfaces. This presentation is focused on our effort to investigate the stability of the the thin flexible structure under electrostatic and lorenz forces opposing each other. In this pre- sentation, we report the result of numerical simulation with some mathematical simplifications. The mathematical model used for the numerical simulation is well studied in the literature. Us- ing forth-order partial differential beam equation, we studied the steady state solutions of the thermo-tunneling beam model using Galerkin method.Essential output parameters of the model in- clude a central contact area measured by its length (delta) and the thermo-tunneling current. Both parameters are determined as a function of the externally applied external potential and magnetic field. Numerical solutions of the model show two possi- ble operating modes: (1) symmetric deformation with negligibly small current; and (2) asymmetric mode where the B-field con- Trols the current and contact area. Under practical values for the externally applied magnetic and electric fields, it has been shown that the second mode is only possible for electrode with very low work functions, e.g. below 0.5 eV. Therefore, novel materials such as Diamond-like carbon films are likely to be essential in thermo-tunneling applications. Copyright © 2012 by ASME.
Enikov, E. T., Madarász, M., & Polyvás, P. P. (2012). Experimental and numerical analysis of ocular tactile tonometry. ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) , 2, 259-267.
Abstract: This article describes the experimental and numerical analysis of a novel trans-scleral tonometer based on the use of an instrumented form of digital palpation tonometry. Similar to manual digital palpation tonometery (estimation of the eye pressure via tactile touch), the novel ocular tactile tonometer utilizes multiple force probes to gather force data from indentation experiments. The presented experimental and numerical analysis shows that force data obtained from these probes correlate with the intraocular pressure (IOP) of the eye. Enucleated porcine eyes were used to validate the approach. The observed hysteresis in the force data was analyzed using an analytical model that accounts for the outflow of the aqueous humor as well as experiments at different indentation rates. Experimental data from eye distention and indentation tests were then used to infer the conditions under which the novel tonometer would be expected to have an accuracy of 1 mmHg. Analysis of the data shows that visco-elastic behavior of the scleral tissue is the primary factor responsible for the observed hysteresis. Further analysis of the data shows that indentation rates should be kept below 0.5 mm/sec for a pressure range of 10-35 mmHg. A conceptual through-the-eye-lid ocular tactile tonometer based on four probes is also presented along with numerical validation of the measured response. Copyright © 2012 by ASME.
McCafferty, S. J., Schwiegerling, J. T., & Enikov, E. T. (2012). Corneal Surface Asphericity, Roughness, and Transverse Contraction after Uniform Scanning Excimer Laser Ablation. INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE , 53(3), 1296-1305.
McCafferty, S. J., Schwiegerling, J. T., & Enikov, E. T. (2012). Corneal surface asphericity, roughness, and transverse contraction after uniform scanning excimer laser ablation. Investigative Ophthalmology and Visual Science , 53(3), 1296-1305.
PMID: 22297493;Abstract: Purpose. To examine the interaction between the excimer laser and residual tissue. Methods. Ten cadaveric porcine eyes with exposed corneal stroma and plastic test spheres underwent uniform 6-mm ablation with a scanning excimer laser. Corneal profilometry of the central 3 mm was measured with submicrometer resolution optical interferometry, before and after uniform excimer ablation. Eleven surface-marked eyes were photomicrographed before and after excimer ablation. Images were superimposed, and mark positional changes were measured. Results. Uniform scanning excimer laser ablation of the corneal stroma produces a significant central steepening and peripheral flattening in the central 3-mm of the diameter. The central 1-mm corneal curvature radius (r) decreased from r = 10.07 ± 0.44 (95% CI) to 7.22 ± 0.30 mm, and the central 2-mm radius decreased from r = 10.16 ± 0.44 to 8.10 ± 0.43 mm. Q values, measuring asphericity in the 2-mm radius of the central cornea, were significantly lower before than after ablation (-5.03 ± 4.01 vs. -52.4 ± 18.7). Surface roughness increased significantly from 0.65 ± 0.06 to 1.75 ± 0.32 μm after ablation. The central 2 mm of the stromal surface contracted by 2.21% ± 0.80% at a sustained temperature of 5°C. Ablation of plastic spheres produced no significant change. Conclusions. The excimer laser interacts with the nonablated residual stromal surface in a characteristic fashion not seen with isotropic, inorganic material. Increases in asphericity, surface roughness, surface contraction, and stromal morphologic changes are supportive of this interaction. The surface changes demonstrated may be indicative of temperature-induced transverse collagen fibril contraction and stress redistribution, or the ablation threshold of the stromal surface may be altered. This phenomenon may be of increased importance using lasers with increased thermal load. © 2012 The Association for Research in Vision and Ophthalmology, Inc.
Zhang, Z. M., Enikov, E. T., & Makansi, T. (2012). Near-field radiative transfer between heavily doped SiGe at elevated temperatures. Journal of Heat Transfer , 134(9).
Abstract: SiGe alloys represent an important type of high-temperature semiconductor material for solid-state energy conversion. In the present study, the near-field radiative heat transfer between heavily doped SiGe plates is investigated. A dielectric function model is formulated based on the previously reported room-temperature mobility and temperature-dependent electric resistivity of several silicon-rich alloys with different doping type and concentration. Fluctuational electrodynamics is used to evaluate the near-field noncontact heat transfer coefficient. The variation of the heat transfer coefficient with doping concentration and temperature is explained according to the change in the optical constants and in the spectral distribution of the near-field heat flux. © 2012 American Society of Mechanical Engineers.
Enikov, E. T., Gamez, C., Kanjiyani, S., Ganji, M., & Gill, J. (2011). Flexible electrode structures for thermo-tunneling applications. ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 , 4(PARTS A AND B), 1657-1663.
Abstract: Combined thermionic emission and tunneling of hot electrons (thermo-tunneling) has emerged as a potential new solid-state cooling technology. Practical implementation of thermo-tunneling, however, requires the formation of a nanometer-sized gap spanning macroscopically significant surfaces. Thermo-tunneling of hot electrons across a few-nanometer gap has application to vacuum electronics, flat panel displays, and holds great potential in thermo-electric cooling and energy generation. Development of new thermo-tunneling applications requires creation of a stable nanometer gap between two surfaces. This presentation is focused on our effort to investigate the feasibility of creating such gaps using distributed electro-magnetic forces arising in thin-film flexible structures. Early efforts based on rigid electrodes showed that the effective tunneling approaches 400 square-micrometers, which albeit small, could lead to useful practical systems. In this presentation, we report a theoretical and experimental investigation of a thin-electrode system which could lead to further increase on the effective tunneling area. The device under study consists of a thin membrane collector electrode (anode) suspended over the emitting electrode (cathode). The structure is placed in a vacuum enclosure with an externally generated magnetic field perpendicular to the current flow in the membrane. The resulting Lorentz force is then directed upwards, separating the two surfaces. A mathematical model of the steady-state operation of the device is presented along with predictions of the contact area and tunneling current. Essential output parameters of the model include a central contact area measured by its length (delta) and the thermo-tunneling current. Both parameters are determined as a function of the externally applied external potential and magnetic field. Numerical solutions of the model show two possible operating modes: (1) symmetric deformation with negligibly small current; and (2) asymmetric mode where the B-field controls the current and contact area. Copyright © 2011 by ASME.
Enikov, E. T., Polyzoev, V., & Gill, J. (2011). Hardware demonstration of classical undergraduate control design methods using matlab real-time windows target environment. ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 , 5, 21-27.
Abstract: Engineering education has the objective of not only presenting the scientific principles, i.e., engineering science, but also of teaching students how to apply these to real problems. Therefore, hands-on laboratories have been an integral part of the engineering curriculum since its inception [1-3]. This presentation will demonstrate the use of a novel low-cost experimental apparatus for use in a typical undergraduate course in control systems taught to mechanical engineering students, i.e. students with limited exposure to electrical engineering. A simple to use, low cost system has been designed that provides a platform for experimentation in areas from basic open loop control, to frequency domain and digital control systems. This paper presents the design of the system, and demonstrates the ability of MAT-LAB tools such as Simulink Real Time Windows Target to illustrate implementation of various aspects of control design. The system setup consists of a DC micro-motor attached to a carbon fiber rod. The angular displacement is measured with an analog potentiometer, which acts as the pivot point for the carbon fiber rod. The DC micro-motor is powered by a low cost, custom circuit board, whos H-bridge allows the motor rotate in either forward or reverse directions. Attached to the micro-motor is a small propeller, providing thrust force to rotate the pendulum about its potentiometer. The circuit board communicates to the host computer using the USB protocol, utilizing usbser.sys to create a virtual COM port. MATLAB uses the serial port object to read and write from the control board. The control board is powered through two USB ports, requiring no external power adaptor or extra cabling. This paper shows the use of feedback linearization to arrive at a system where classical linear control design methods can be used. The project was tested in a classical control systems design class offered to senior-level mechanical engineering students. Student feedback and survey data on the effectiveness of the module is also presented. Copyright © 2011 by ASME.
Polyvás, P. P., Enikov, E. T., Peyman, G., & Polyzoev, V. (2011). Trans-scleral tonometry: Mechanical palpation of the eye. ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 , 2, 229-233.
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 . 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.
Sagi, O. T., Maynard, D., & Enikov, E. (2011). Capacitive transducer for condition based maintenance after harsh landing events. AUTOTESTCON (Proceedings) , 286-291.
Abstract: The objective of this work is to identify design parameters for a capacitive sensor designed to recognize and record helicopter harsh landing events. Harsh landing events are typically associated with landing speeds exceeding 2.5 m/s  and require mandatory structural inspection resulting in down-times that could last a week or longer. In cases where no visible damage occurs, harsh-landing events might be difficult to identify and record. This paper presents a finite element analysis of the acceleration profile at different locations of the skid of a Bell 206 L4 helicopter which is then used to design and test a low-cost capacitive sensor for monitoring harsh landing events. Time history and histograms of the acceleration signal during normal and harsh landings are presented. The capacitive accelerometer is designed to operate in the 10g to 360g range. The sensor is integrated directly on a wiring board and is readout by a micro-controller with a capacitive ASIC. Details of the sensor design, fabrication, and testing are presented. The presented material also provides hard-to-find design data on the structural accelerations which can occur during harsh landing. © 2011 IEEE.
Scott, J., & Enikov, E. T. (2011). Novel temperature compensation technique for force-sensing piezoresistive devices. Journal of Micromechanics and Microengineering , 21(11).
Abstract: A novel stress-insensitive piezoresistor in the shape of an annulus has been developed to be used in conjunction with a piezoresistive bridge for temperature-compensated force measurements. Under uniform stress conditions, the annular resistor shows near-zero stress sensitivity and a linear response to temperature excitation within test conditions of 24-34 °C. Annular resistors were placed in close proximity to stress-sensitive elements in order to detect local temperature fluctuations. Experiments evaluating the performance of the temperature compensator while testing force sensitivity showed a thermal rejection ratio of 37.2 dB and near elimination of low-frequency noise (drift) below 0.07 Hz. Potential applications of this annular resistor include use in multi-axis force sensors for force feedback microassembly, improvements in the simplicity and robustness of high precision microgram sensitive balances, higher accuracy for silicon diaphragm-based pressure sensors and simple temperature compensation for AFM cantilevers. © 2011 IOP Publishing Ltd.
Szabo, Z., Ganji, M., & Enikov, E. T. (2011). Development of voice-coil micro-actuator for 3-D virtual tactile displays. ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 , 7(PARTS A AND B), 1027-1033.
Abstract: An electromagnetic micro-actuator operating on the principle of voice-coil actuators is presented. Using finite element analysis of several conceptual designs of actuators [1-3], it was established that the voice-coil type device (where the coil is the moving part) has most beneficial characteristics for the envisioned application. These include sufficient force over a relatively large distance, allowing tactile stimulation of surfaces with irregular shape, fast response, and small footprint that matches the density of the tactile sensory neurons in the finger. Finite element analysis based on ANSYS was used to determine the dimensions of the components of the actuator. In comparison to earlier designs [3-5], this novel device has smaller sizes (2.28 mm in diameter and 7 mm in length), which makes it suitable for use in an array to be worn on the fingertip. Based on the static measurements of a test prototype, it is estimated, that the micro-actuator can produce at least 26 mN of repulsive force on the fingertip over a stroke of 2100 μm with a peak force of 34 mN. The driving circuit operates with 13.5V and generates a vibration frequency of up to 265 Hz without significant change of the force-displacement characteristics. In the higher frequency range (above 100 Hz) the actuator provides at least 15 mN of force over a stroke of 2300 μm, and a peak force of 21mN. The perceivability of the device on human fingertip approves the expectations drawn from the fact that all of the above parameters meet the required values of the thresholds of the human perception known from  and . Due to its increased stroke, the voice-coil micro-actuator proved to be very suitable for the envisioned application allowing contact with the curved surface of the fingertip. Copyright © 2011 by ASME.
Vohnout, S., Engelman, M., & Enikov, E. (2011). Miniature MEMS-based data recorder for prognostics and health management (PHM). IEEE Instrumentation and Measurement Magazine , 14(4), 18-26.
Abstract: Novel prognostic sensors and reasoner algorithms are the core technology for detecting defects caused by accumulation of fatigue damage in electrical and mechanical systems over time. However, serious technical challenges to implementing a general health management strategy for helicopters and military aircraft still exist. For example, severe heat and vibration make it difficult to distinguish fault signatures from environmental noise. Moreover, bearing loads are very dynamic, making it difficult to distinguish subtle wear-out signatures from normal acoustic patterns. Detection can be improved by increasing the number of sensor locations, but this option is unattractive from the standpoint of added cost, weight, and data overhead of such a system. © 2011 IEEE.
Zhang, Z. M., Enikov, E. T., & Makansi, T. (2011). Near-field radiative transfer between heavily doped SiGe at elevated temperatures. ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011 , 10(PARTS A AND B), 283-291.
Abstract: SiGe alloys represent an important type of high-temperature semiconductor material for solid-state energy conversion. In the present study, the near-field radiative heat transfer between heavily doped SiGe plates is investigated. A dielectric function model is formulated based on the previously reported room-temperature mobility and temperature-dependent electric resistivity of several silicon-rich alloys with different doping type and concentration. The fluctuational electrodynamics is used to evaluate the near-field noncontact heat transfer coefficient. The variation of the heat transfer coefficient with doping concentration and temperature is explained according to the change in the optical constants and in the spectral distribution of the near-field heat flux. Copyright © 2011 by ASME.
Deng, K., & Enikov, E. T. (2010). Design and development of a pulsed electromagnetic micro-actuator for 3D virtual tactile displays. MECHATRONICS , 20(4), 503-509.
Abstract: The design and analysis of a miniature electromagnetic actuator for use in a novel virtual tactile display is described. The actuator operates in repulsive mode so that it can be used for vibro-tactile stimulation of a human fingertip. Pulsed current and permanent magnet based approaches are investigated and compared. Four frequencies (10, 50, 100, and 150 Hz) were used to test the perception limit of three human subjects. The results indicated that the perception is not strongly dependent on frequency in the test range. The required stimulation energy of individual pulses was estimated to be below 57 micro-Joules, while the average peak-force needed for reliable stimulation was 59 milli-Newtons. The perception of simple test shapes was also tested by attaching the actuator onto the fingertip of the human subjects and turning it on and off as a function of its position. © 2010 Elsevier Ltd. All rights reserved.
Engelman, M., Judkins, J., Vohnout, S., & Enikov, E. (2010). Miniature MEMS-based data recorder for prognostics and health management (PHM). AUTOTESTCON (Proceedings) , 343-350.
Abstract: Novel prognostic sensors and reasoner algorithms are the core technology for detecting defects caused by accumulation of fatigue damage in electrical and mechanical systems over time. However, serious technical challenges to implementing a general health management strategy for helicopters and military aircraft still exist. For example, severe heat and vibration make it difficult to distinguish fault signatures from environmental noise. Moreover, bearing loads are very dynamic, making it difficult to distinguish subtle wear-out signatures from normal acoustic patterns. Detection can be improved by increasing the number of sensor locations, but this option is unattractive from the standpoint of added cost, weight, and data overhead of such a system. Our approach is to integrate MEMS sensors with a standard commercial microcontroller and measurement electronics. In this way, prognostic sensors can be positioned closer to the stressed components and provide higher fidelity data with lower cost. We present an innovative design for a prognostics and health management (PHM) data recorder that will facilitate sense-and-response logistics, and provide a small and inexpensive package. This low-cost, low-power, and lightweight solution is based largely on COTS components; it is implemented using a standard low-power lightweight microcontroller core and COTS MEMS sensors to record and process local temperature and vibration data, and status reporting is implemented using a short range wireless transceiver. © 2010 IEEE.
Eppel, A., Enikov, E. T., Insperger, T., & Gabor, S. (2010). Feasibility study of optical detection of chatter vibration during milling. International Journal of Optomechatronics , 4(2), 195-214.
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.
Deng, K., Enikov, E. T., & Polyzoev, V. D. (2009). Development of a shape conveying interface based on tactile feedback. 2009 ICME International Conference on Complex Medical Engineering, CME 2009 .
Abstract: A shape conveying interface based on tactile feedback is developed in this paper. To deliver the reference shape, the electromagnetic (EM) position sensors and wearable permanent magnet based EM actuator are used to provide the estimated 3D image by the user's scanning. Principle and experimental results of EM position measurement are provided. ANSYS simulation is used to design a proper dimension of solenoid to drive the permanent magnet actuator. With the designed actuator, the 63.57 mN actuation force at peak current is estimated from measured force-current curve. 50-Hz operation which has been shown to be optimal working frequency is used to produce vibratory stimulation to user's finger. The shape perception experiments performed by 2 volunteers showed that majority of shapes are able to be delivered. More cues may be incorporated in order to improve successful rate of the shape delivery. ©2009 IEEE.
Enikov, E. T., Gibson, M. T., & Ritty, S. J. (2009). Novel extrusion system for the encapsulation of drug releasing bio-medical micro-robots. 2009 ICME International Conference on Complex Medical Engineering, CME 2009 .
Abstract: This paper examines the design and testing of a novel extrusion system for the biocompatible coating of drug delivering micro-robots. The encapsulation system creates monodisperse droplets of sodium alginate containing the micro-robots within a coaxial laminar flow of a continuous oil phase. The extrusion process allows the experimenter to control the size of the drug carrying droplets which have been subsequently tested as vehicles to deliver a model drug (Horseradish peroxidase). Comparison with other coating techniques such as dip-coating shows significant increase in the drug storing capacity. A demonstration of the use of ultrasound as a possible trigger of the drug release has also been presented. The significant increase in the observed drug release rate shows enhancement over previously tested passive diffusion and magnetic modulation methods. Together, these two aspects of micro-robotic drug delivery concept introduce a new approach to drug-delivering microrobots with large drug-storage capacity, ability to propel the robots using magnetic forces, and trigger the drugrelease by remote application of ultrasonic stimulation. ©2009 IEEE.
Luce, A. V., Enikov, E. T., & Nelson, B. J. (2009). Design of automated digital eye palpation exam for intraocular pressure measurement. 2009 ICME International Conference on Complex Medical Engineering, CME 2009 .
Abstract: Elevated intraocular pressure (IOP) is a major risk factor for the degenerative eye disease glaucoma. Accurate indirect measurements of IOP are essential for glaucoma diagnosis and screening. This work presents an experiment developed to measure IOP in-vitro by simulating the technique of digital palpitation tonometry, a technique in which a trained examiner palpates the eyeball using the fingertips of both index fingers to "feel" the stiffness of the eye. The qualitative nature of this method and errors introduced by the subjectivity of the examiner mean that it is rarely used in comparison with other modern-day tonometry methods. However, this technique offers several potential advantages in that it can be performed outside of a clinical setting without the need for instrument sterilization or local anesthesia and may be less subject to measurement errors occurring in patients who have undergone refractive laser eye surgery. In order to quantify the mechanics of digital palpation tonometry, an automated experiment to measure the intraocular pressure of enucleated porcine eyeballs using mechanized digital palpation was designed and tested. This experiment has direct applications towards the development of a next-generation tonometer for glaucoma treatment. ©2009 IEEE.
Polyzoev, V., Enikov, E., Heinze, B., & Yoon, J. (2009). Magnetic particle enhanced microcantilever biosensor for rapid and sensitive E. coli detection. ISOT 2009 - International Symposium on Optomechatronic Technologies , 387-391.
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.
Enikov, E. T., & Makansi, T. (2008). Analysis of nanometer vacuum gap formation in thermo-tunneling devices. NANOTECHNOLOGY , 19(7).
PMID: 21817651;Abstract: Combined thermionic emission and tunneling of hot electrons (thermo-tunneling) has emerged as a potential new solid-state cooling technology. Practical implementation of thermo-tunneling, however, requires the formation of a nanometer-sized gap spanning macroscopically significant surfaces. This paper describes a numerical and experimental investigation into the formation of a nanometer-sized tunneling gap based on the combined action of electrostatic, elastic and Lorentz forces. Experimental data reported here were used to tune the model and extract estimates for the size of the tunneling area and the gap size, respectively. The effect of changing the strength of the magnetic field was also investigated. The presented one-dimensional (1D) analysis of the relative magnitudes of these forces indicates possible stable operation. © IOP Publishing Ltd.
Deng, K., Enikov, E. T., & Zhang, H. (2007). Development of a pulsed electromagnetic micro-actuator for 3D tactile displays. IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM .
Abstract: We propose an electromagnetic micro-actuator for tactile displays based on magnetization of the solenoid by a sharp current pulse. By applying DC to the solenoid, the force-current relation in a static configuration of the actuator is determined. An experiment to produce vibrating stimulation on human fingertip is presented using a single actuator unit. Four frequencies (10, 50, 100, and 150Hz) were used to test the perception limit of two volunteer subjects. The results indicated that the perception is not strongly dependent on frequency in the test range. The working frequency of the device was, therefore, limited to 50Hz to allow the use of relative high charge storing capacitor and larger heat dissipation intervals. The actuator was then actuated as a function of its real-time position to "display" several virtual shapes. The results showed that five out of six simple geometries were perceived correctly. ©2007 IEEE.
White, E. L., & Enikov, E. T. (2007). Self-aligning electrostatic gripper for assembly of millimeter-sized parts. IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM .
Abstract: In this study, the performance of several electrostatic grippers is evaluated. These grippers are designed to align millimeter scale parts to matching electrode geometry on the gripper surface. Friction between the gripper and part is overcome through ultrasonic excitation of the gripper by a piezoceramic element. The effect of different frequencies and amplitudes of excitation on alignment were observed. Additionally, the use of ultrasonic excitation to aid in part release after clamping was investigated. Under ideal conditions, part motion was most frequently observed in certain excitation frequency windows, which correspond to resonant modes of the part-gripper system. ©2007 IEEE.
Djakov, B. E., Enikov, R., Oliver, D. H., Hrabovsky, M., & Kopecky, V. (2006). Chromatic monitoring of DC plasma torches: The latest developments. PLASMA PROCESSES AND POLYMERS , 3(2), 170-173.
Enikov, E. T. (2006). Electrodeposited micro-actuators: A simple tool for impedance-based sensing. ECS Transactions , 3(10), 339-350.
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.
Enikov, E. T., & Seo, G. S. (2006). Numerical analysis of muscle-like ionic polymer actuators. Biotechnology Progress , 22(1), 96-105.
PMID: 16454498;Abstract: Ionic polymers are a promising material for the development of muscle-like actuators. These materials are capable of undergoing significant deformation when structured as metal-polymer-metal composite sheets. The mechanical characteristics of these sheets, such as flexibility, softness, and ability to undergo large deformation in direct contact with water, have led some to consider these as possible artificial muscles. This paper describes the numerical analysis of an electrochemical model of the deformation of muscle-like polymers. A general continuum model describing the transport and deformation processes of these actuators is briefly presented, along with a detailed description of the simulation scheme used to predict deformation, current, and mass transport. The predictions of the model are compared with experimental data, indicating a significant role of water transport in the large-scale deformation. The model is also used to draw a comparison between the performance of natural muscles and muscle-like polymer actuators. © 2006 American Chemical Society and American Institute of Chemical Engineers.
Katagiri, Y., & Enikov, E. T. (2006). Proceedings of SPIE - The International Society for Opticl Engineering: Introduction. Proceedings of SPIE - The International Society for Optical Engineering , 6376, ix-x.
Palaria, A., & Enikov, E. T. (2006). Experimental analysis of the stability of electrostatic bits for assisted nano-assembly. JOURNAL OF ELECTROSTATICS , 64(1), 1-9.
Abstract: Scanning probe microscopy(SPM)-based nanolithography with injected charges into layered electrets, such as silicon dioxide (SiO2) and silicon nitride, is a promising tool with far-reaching applications, such as controlled nano-assembly of macro-molecules and data storage. Despite its potential, some practical limitations exist. This paper describes an experimental investigation of the process of charging and charge dissipation in SiO2 using an AFM probe tip and surface potential (Kelvin probe) microscopy. The stability of charge bits on hexamethyl disilazane(HMDS)-treated SiO2 under low dielectric constant liquids, fluorocarbon, and benzene has been demonstrated. Results from a numerical simulation of a theoretical charging model, in which the charge traps are assumed to be localized on the silicon/SiO2 interface, are also presented. The charge transport mechanism considered is modified Fowler-Nordheim tunneling. © 2005 Elsevier B.V. All rights reserved.
Enikov, E. T., & Lazarov, K. V. (2005). Micro-mechanical switch array for meso-scale actuation. SENSORS AND ACTUATORS A-PHYSICAL , 121(1), 282-293.
Enikov, E. T., & Lazarov, K. V. (2005). Micro-mechanical switch array for meso-scale actuation. Sensors and Actuators, A: Physical , 121(1), 282-293.
Abstract: Traditional micro-electro mechanical systems (MEMS) actuators have limited stroke and force characteristics. This paper describes the development of a hybrid actuation solution, which utilizes a micro-machined actuator array to provide switching of the mechanical motion of a larger meso-scale piezo-electric actuator. One motivating application of this technology is the development of a tactile display, where discrete mechanical actuators apply vibratory excitation at discrete locations on the skin. Specifically, this paper describes the development, fabrication, and characterization of a 4 × 5 micro-actuator array of individual vibrating pixels for fingertip tactile communication. The individual pixels are turned on and off by pairs of microscopic thermal actuators, while the main vibration is generated by a vibrating piezo-electric plate. The fabrication sequence and actuation performance of the array are also presented. © 2005 Elsevier B.V. All rights reserved.
Enikov, E. T., & Seo, G. S. (2005). Analysis of water and proton fluxes in ion-exchange polymer-metal composite (IPMC) actuators subjected to large external potentials. SENSORS AND ACTUATORS A-PHYSICAL , 122(2), 264-272.
Enikov, E. T., & Seo, G. S. (2005). Analysis of water and proton fluxes in ion-exchange polymer-metal composite (IPMC) actuators subjected to large external potentials. Sensors and Actuators, A: Physical , 122(2), 264-272.
Abstract: An analysis is conducted of a novel ion-exchange polymer-metal composite (IPMC) actuator under large external voltage. The model is simplified to a three-component system comprised of a fixed negatively charged polymeric matrix, protons, and free water molecules within the polymer matrix. The proposed coupled model includes mass transport in the membrane, chemical reactions at boundaries, and deformation as a function of a concentration of water molecules. The electrochemical process occurring at both electrodes are the boundary conditions analyzed during the deformation of the actuator in a regime of large voltage (over 1.2 V). This coupled model successfully captures the stress relaxation phenomenon due to water redistribution governed by diffusion. The fabrication process and testing apparatus are also described. Comparison of simulations and experimental data showed good agreement. © 2005 Elsevier B.V. All rights reserved.
Enikov, E. T., & Seo, G. S. (2005). Experimental analysis of current and deformation of ion-exchange polymer metal composite actuators. EXPERIMENTAL MECHANICS , 45(4), 383-391.
Abstract: In this paper we describe the experimental analysis of a novel ion-exchange polymer metal composite (IPMC) actuator under large external voltage. The experimental analysis is supplemented with a coupled thermodynamic model, which includes mass transport across the thickness of the polymer actuator, chemical reactions at boundaries, and deformation as a function of the solvent (water) distribution. In this paper, the case of large electrode potentials (over 1.2 V) has been analyzed experimentally and theoretically. At these voltage levels, electrochemical reactions take place at both electrodes. These are used in the framework of overpotential theory to develop boundary conditions for the water transport in the bulk of polymer. The model is then simplified to a three-component system comprised of a fixed negatively charged polymeric matrix, protons, and free water molecules within the polymer matrix. Among these species, water molecules are considered to be the dominant species responsible for the deformation of the IPMC actuators. Experiments conducted at different initial water contents are described and discussed in the context of the proposed deformation mechanism. Comparison of numerical simulations with experimental data shows good agreemenent. © 2005 Society for Experimental Mechanics.
Enikov, E. T., Kedar, S. S., & Lazarov, K. V. (2005). Analytical model for analysis and design of V-shaped thermal microactuators. JOURNAL OF MICROELECTROMECHANICAL SYSTEMS , 14(4), 788-798.
Abstract: An analytical solution of the thermoelastic bending/budding problem of thermal microactuators is presented. V-shaped beam actuators are modeled using the theory of beam-column buckling. Axial (longitudinal) deformations including first-order nonlinear strain-displacement relations and thermal strains are included. The resulting nonlinear transcendental equations for the reaction forces are solved numerically and the solutions are compared with a nonlinear finite element (FE) model. A test actuator has also been fabricated and characterized. The obtained accuracy of the prediction is within 1.1% of the nonlinear FE solution and agrees well with the experimental data. A corresponding one-dimensional (1-D) heat transfer model has also been developed and validated against experimental i-V measurements at various temperatures. The developed analytical models are then used to analyze maximum stress and the heat transfer paths. It has been confirmed that the heat flux toward the substrate is a dominant heat dissipation route in sacrificially released devices. © 2005 IEEE.
Enikov, E. T., Minkov, L. L., & Clark, S. (2005). Microassembly experiments with transparent electrostatic gripper under optical and vision-based control. IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS , 52(4), 1005-1012.
Abstract: This paper describes the assembly experiments conducted with a novel miniature assembly cell for microelectro-mechanical systems. The cell utilizes a novel transparent electro-static gripper and uses several disparate sensing modalities for position control: computer vision for part alignment with respect to the gripper, a fiber-coupled laser, and a position-sensitive detector for part to assembly alignment. The assembly experiments performed indicate that the gripping force and stage positioning accuracy of the gripper are sufficient for insertion of micromachined parts into slots etched in silicon substrates. Details of the cell operation, the control algorithm used, and their limitations are also provided. Potential applications of the developed assembly cell are assembly of miniature optical systems, integration of optoelectronics, such as laser diodes with CMOS, and epitaxial lift-off of thin films used in optoelectronic devices. © 2005 IEEE.
Miller, T. E., & Enikov, E. T. (2005). Electric field-assisted assembly of type-I collagen for applications in biomedical micro-systems. Advances in Bioengineering, BED , 57, 65-68.
Abstract: In the field of nanotechnology and applied engineering, an area that has received a great deal of attention is that of nanoassembly. The objective of this study was to demonstrate nanoassembly of type-I collagen on specified surfaces in response to an electric field. Two, otherwise identical, collagen solutions were prepared and adjusted to pHs of 5.5 and 8. The isoelectric fosusing point of collagen occurs at pH=6.7 which implies that the suspended collagen fibers in the aforementioned solutions possessed a net positive or negative charge, respectively. In each collagen solution, one volt was applied through a set of submerged electrodes for one minute. Atomic force microscopy was used to detect if and where assembly had occurred on the electrodes. The positively charged fibrils (pH=5.5) assembled on the negative electrode, but not on the positive electrode. The negatively charged fibrils (pH=8) assembled only on the positive electrode, but not on the negative electrode. In both cases, assembly occurred on the electrode of opposite charge of the suspended collagen fibrils, which was anticipated. The assembly of the positively charged fibrils (pH=5.5) on the cathode produced larger fibers than the fibers that were produced by the negatively charged fibrils (pH=8) on the anode. This indicated the more favorable environment for nanoassembly was the positively charged fibril solution (pH=5.5). Copyright © 2005 by ASME.
Rose, S. E., Jones, J. F., & Enikov, E. T. (2005). Development of a high sensitivity three-axis force/torque sensor for microassembly. American Society of Mechanical Engineers, Micro-Electro Mechanical Systems Division, (Publications) MEMS , 7 MEMS, 405-409.
Abstract: There is a growing need for multi-axis force torque (F/T) sensors to aid in the assembly of micro-scale devices. Many current generation robotic microassembly systems lack the force-feedback needed to facilitate automating common assembly tasks, such as peg-in-hole insertions. Currently, most microassembly operations use vision systems to align components being assembled. However, it is difficult to view high aspect ratio component assemblies under high magnification due to the resulting limited depth-of-field. In addition, this difficulty is compounded as assembly tolerances approach dimensions resolvable with optics or if the mating parts are delicate. This paper describes the development of a high sensitivity F/T sensor. Optimal design theory was applied to determine the configuration that would result in the most sensitive and accurate sensor: Calibration experiments demonstrated that the sensor can resolve down to 200μN and possibly less. Copyright © 2005 by ASME.
Enikov, E. T., & Lazarov, K. V. (2004). Hybrid micro-meso mechanical switch array for tactile displays. American Society of Mechanical Engineers, Micro-Electro Mechanical Systems Division, (Publications) MEMS , 181-188.
Abstract: Traditional MEMS actuators have limited stroke and force characteristics. This paper describes the development of a novel hybrid actuation solution, which utilizes a micromachined actuator array to provide switching of mechanical motion of a larger meso-scale piezo-electric actuator. One motivating application of this technology is the development of a tactile display, where discrete mechanical actuators apply vibratory excitation at discrete locations on the skin. Specifically, this paper describes the development fabrication and characterization of a 4 × 5 micro-actuator array of individual vibrating pixels for fingertip tactile communication. The individual pixels are turned ON and OFF by pairs of microscopic thermal actuators, while the main vibration is generated by a vibrating piezo-electric plate. A thermo-electric and non-linear thermo-elastic models have been developed to account for the temperature dependence of the electrical resistance and the lateral buckling of the hot, respectively. Comparison between analytical and finite element models indicated very good agreement, confirming that the buckling of the hot arm has most significant impact in the overall actuator performance. The fabrication sequence and the actuation performance of the array are also presented. Copyright © 2004 by ASME.
Enikov, E. T., & Minkov, L. (2004). Micro-assembly and packaging of MEMS using optically transparent electrostatic gripper. American Society of Mechanical Engineers, Manufacturing Engineering Division, MED , 15, 511-518.
Abstract: This paper describes the assembly experiments with a novel miniature assembly cell for micro-electromechanical systems (MEMS). The cell utilizes a transparent electrostatic gripper and uses several disparate sensing modalities for position control: computer vision for part alignment with respect to the gripper, a fiber-coupled laser, and a position sensitive detector (PSD) for part to assembly alignment. Assembly experiments indicate that the gripping force and stage positioning accuracy are sufficient for insertion of 500μm wide parts in 550 μm wide slots etched in silicon wafers. Details on the cell operation, the control algorithm used and their limitations are also provided. Potential applications of the developed assembly cell are assembly of miniature optical systems, integration of optoelectronics, such as laser diodes with CMOS, and epitaxial lift-off (ELO) of thin films used in optoelectronic devices. Copyright © 2004 by ASME.
Enikov, E. T., & Palaria, A. (2004). Charge writing in silicon-silicon dioxide for nano-assembly. NANOTECHNOLOGY , 15(9), 1211-1216.
Abstract: Interest in using electrostatics for active nano-assembly has grown significantly over the last five years. One common electret structure for such electrostatic constructs is the silicon-silicon dioxide interface. In this paper, an experimental and mathematical analysis of the process of writing negative charge spots in Si-SiO2 is presented. It is demonstrated that controlling the spread of the charge can reduce the spot size and the drop in written potential. Simulation results of a one-dimensional charging model that assumes tunnelling of electrons through the oxide and trapping within SiO2 are presented and compared with the experimental data. The model assumes charge trapping at the Si-SiO2 interface and none at the oxide-air interface or within the oxide bulk. Conducted experiments also show that although the lateral spread of charge places a lower limit on the minimum spot size in silicon-silicon dioxide structures, the use of a hydrophobic hexamethyldisilazane layer can be effective in improving the size stability of the written electrical spots.
Enikov, E. T., & Lazarov, K. (2003). PCB-integrated metallic thermal micro-actuators. SENSORS AND ACTUATORS A-PHYSICAL , 105(1), 76-82.
Enikov, E. T., & Lazarov, K. (2003). PCB-integrated metallic thermal micro-actuators. Sensors and Actuators, A: Physical , 105(1), 76-82.
Abstract: The development of thermal micro-actuators on printed circuit boards is described. The fabricated metal actuators are shown to have similar displacement characteristics when compared with silicon-based devices described in the literature. The actuators are benchmarked with respect to power consumption, stroke, and response time. It is further demonstrated that simple analytical estimates for the response time are in good agreement with the experimental measurements and finite element analysis. The thermal cooling transient times are captured using a two-step constant-current excitation method. The fabrication process and potential application areas of the developed device are also provided. © 2003 Elsevier Science B.V. All rights reserved.
Enikov, E. T., & Lazarov, K. V. (2003). Composite Thermal Micro-Actuator Array for Tactile Displays. Proceedings of SPIE - The International Society for Optical Engineering , 5055, 258-267.
Abstract: Tactile perception of complex symbols through tactile stimulation is an exciting application of a phenomenon known as tactile illusion (TI). Sensation of motion on the skin can be produced by a limited number of discrete mechanical actuators applying light pressure over the skin. This phenomenon can thus be used as a neurophysiological testing tool to determine central and peripheral nervous system injury as well as providing an additional human-machine communication channel. This paper describes the development of a 4 × 5 actuator array of individual vibrating pixels for fingertip tactile communication. The array is approximately one square centimeter and utilizes novel micro-clutch MEMS technology. The individual pixels are turned ON and OFF by pairs of microscopic composite thermal actuators, while the main vibration is generated by a vibrating piezo-electric plate. The physiological parameters required for inducing tactile illusion are described. The fabrication sequence for the thermal micro-actuators along with actuation results are also presented.
Enikov, E. T., & Lazarov, K. V. (2003). Metallic microactuators based on sacrificial layer SU8 release. American Society of Mechanical Engineers, Micro-Electromechanical Systems Division Publication (MEMS) , 5, 133-139.
Abstract: Thermal micro-actuators are a promising solution to the need for large-displacement, low-power MEMS actuators. Potential applications of these devices are micro-relays, tunable impedance RF networks, and miniature medical instrumentation. In this paper the development of thermal microactuators based on SU8 is described. A polymeric sacrificial layer allows the removal of the SU8 mold to occur without the use of harsh etching conditions. In addition to silicon non-traditional for MEMS substrates such as RF-printed circuit boards have also been successfully utilized to fabricate the devices. The PCB-based devices exhibited similar characteristics, thus opening the possibility of integrating RF MEMS directly on PCBs. The actuators were benchmarked with respect to power consumption, stroke, and response time. The fabricated nickel actuators are shown to be robust with displacements in the range of 76 micrometers using 80 mW of power. Actual cooling transients were captured using a two-step constant-current excitation method. It is further demonstrated through analytical models that the thermal cooling times limit the bandwidth of these devices below 1KHz. Several commercially relevant applications of the developed actuators are also discussed. One such application is a vibro-tactile display for disabled individuals.
Enikov, E. T., Clark, S., & Minkov, L. (2003). Micro-assembly cell with dual optical/computer vision control for electrostatic gripping of MEMS. Proceedings of SPIE - The International Society for Optical Engineering , 5267, 269-280.
Abstract: This paper describes the development of a miniature assembly cell for microsystems. The cell utilizes a transparent electrostatic gripper allowing the use of computer vision for part alignment with respect to the gripper. Part to assembly alignment is achieved via optical triangulation using a fiber-coupled laser and a position sensitive detector (PSD). The system layout, principle of operation and design are described along with the visual and optical control algorithms and their implementation. Experimental measurements of the performance of the stage indicate normal and tangential gripping forces in the range of 0.03-2.5 mN and 1.-9. mN respectively. The visual search algorithm limits the feature tracking speed to 111ms /search. The alignment accuracy of the visual and optical proportional position feedback controls were determined to be ±7 μm and ±10 μm respectively.
Enikov, E. T., & Seo, G. S. (2002). Large deformation model of ion-exchange actuators using electrochemical potentials. Proceedings of SPIE - The International Society for Optical Engineering , 4695, 199-209.
Abstract: A composite actuator based on a polymer electrolyte and metal electrodes is described. Electrode deposition is described qualitatively with corresponding experimental results. A general continuum model describing the transport and deformation of solid polymer electrolyte processes is developed. The formulation is based on global integral postulates for the conservation of mass, momentum, energy, charge, and the second law of thermodynamics. The global equations are then localized in the volume and on the material surfaces bounding the polymer. The model is simplified to a three component system of a fixed negatively charged polymeric matrix, diffusing hydroxonium ions, and free water within the polymer matrix. Contrary to the existing electrostatic models, the deformation is attributed to water induced swelling. The proposed internal pressure based model includes the stress relaxation phenomenon due to water redistribution governed by Darcy's law.
Sun, Y., Nelson, B. J., Potasek, D. P., & Enikov, E. (2002). A bulk microfabricated multi-axis capacitive cellular force sensor using transverse comb drives. JOURNAL OF MICROMECHANICS AND MICROENGINEERING , 12(6), 832-840.
Abstract: This paper presents design, fabrication and calibration results for a novel 2-DOF capacitive force sensor capable of resolving forces up to 490 μN with a resolution of 0.01 μN in x, and up to 900 μN with a resolution of 0.24 μN in y. A simple fabrication process using deep reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafers forms the 3D high aspect ratio structure. A transverse mode comb drive movement is used to greatly improve device sensitivity. Among other advantages of the developed process is a dice-free release of wafer structures, allowing fragile structures to be individually packaged. Notching or footing effects and bowing effects are well-known problems in DRIE on SOI wafers. Techniques to overcome notching and bowing effects using a PlasmaTherm SLR-770 etcher are presented that do not require hardware modifications. The application of the force sensor is for providing real-time force feedback during individual cell manipulation tasks.
Enikov, E. T., & Lazarov, K. V. (2001). Optically transparent gripper for microassembly. MICROROBOTICS AND MICROASSEMBLY III , 4568, 40-49.
Enikov, E. T., & Lazarov, K. V. (2001). Optically transparent gripper for microassembly. Proceedings of SPIE - The International Society for Optical Engineering , 4568, 40-49.
Abstract: Production of complex Micro-Opto Electro-Mechanical Systems (MOEMS) often requires assembly of a system from individual components built by mutually incompatible processes. This fabrication step also constitutes the largest portion of the total cost (about 80%), and is one of the major roadblocks to successfully implementing a complex microsystem. Our previous experience with such systems shows, that gripping and manipulation of microparts significantly differs from the assembly of macroscopic devices. The main difference stems from the increased role of the surface electrostatic forces and the reduced influence of body forces such as gravity. This paper describes one possible use of the surface forces in the development of a novel optically transparent electrostatic microgripper. The principle of operation, design and simulation of the new device are described. Several models describing the gripping force are also presented. The out-of-plane and in-plane holding (frictional) forces are measured as a function of the applied voltage for two common materials - silicon and nickel. The fabrication sequence and the materials used are discussed.
Boyd, J. G., & Enikov, E. T. (2000). Finite element analysis of electric field assisted bonding. Proceedings of SPIE - The International Society for Optical Engineering , 3992, 306-318.
Abstract: An anodic bond is modeled as a moving nonmaterial line forming the intersection of three material surfaces representing the unbonded conductor, the unbonded insulator, and the bonded interface. The component mass balance equations, Gauss' law, and the linear momentum equations are placed in a finite element formulation, which is used to predict the evolution of the sodium ion concentration, electric potential, and stress during anodic bonding of Pyrex glass and silicon.
Enikov, E. T., & Boyd, J. G. (2000). A thermodynamic field theory for anodic bonding of micro electro-mechanical systems (MEMS). INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE , 38(2), 135-158.
Enikov, E. T., & Boyd, J. G. (2000). Electroplated electro-fluidic interconnects for chemical sensors. SENSORS AND ACTUATORS A-PHYSICAL , 84(1-2), 161-164.
Enikov, E. T., & Boyd, J. G. (2000). Electroplated electro-fluidic interconnects for chemical sensors. Sensors and Actuators, A: Physical , 84(1), 161-164.
Abstract: A wet chip electro-fluidic packaging technology based on electroplating is described. An electroplated gold seal provides the sensor's fluid connection to a silicon multi-chip module. A hermetic seal is obtained using the gold-silicon eutectic bond. The sensor's electrical connections to the multi-chip module are made by eutectic bonding electroplated gold-tin solder bumps on the sensor to gold pads on the substrate. The fluid and electrical connections are made simultaneously, and the process is compatible with the flip-chip bonding technique.
Enikov, E. T., & Boyd, J. G. (2000). Finite-element formulation for anodic bonding. Smart Materials and Structures , 9(6), 737-750.
Abstract: An anodic bond is modeled as a moving non-material line forming the intersection of three material surfaces representing the unbonded conductor, the unbonded insulator, and the bonded interface. The component mass balance equations, Gauss' law, and the linear momentum equations are cast in a finite-element formulation, which is used to predict the evolution of the sodium ion concentration, electric potential, and stress during the anodic bonding of Pyrex glass and silicon. The method is applicable to the viscoplasticity of solid electrolytes, and the volume and interface free energies can be modified to model electromechanical interface phenomena such as debonding, space charge accumulation and sliding at grain boundaries in ionic crystals, and a cohesive zone theory of piezoelectric fracture.
Enikov, E. T., & Nelson, B. J. (2000). Electrotransport and deformation model of ion exchange membrane based actuators. Proceedings of SPIE - The International Society for Optical Engineering , 3987, 129-139.
Abstract: A continuum mechanical model of Nafion based metal-polymer actuators is presented. Global integral postulates are written for the conservation of mass, momentum, energy, and charge, Gauss' law, and the second law of thermodynamics. The global equations are then localized in the volume and on the material surfaces bounding the polymer. A finite element formulation is used to predict the evolution of the counter ion concentration, 'free' water content, electric potential, and stress/strain during actuation. The model includes stress relaxation phenomena due to water flow governed by Darcy's law.
Enikov, E. T., & Nelson, B. J. (2000). Electrotransport and deformation model of ion exchange membrane based actuators. SMART STRUCTURES AND MATERIALS 2000: ELECTROACTIVE POLYMER ACTUATORS AND DEVICES (EAPAD) , 3987, 129-139.
Enikov, E. T., & Nelson, B. J. (2000). Three-dimensional microfabrication for a multi-degree-of-freedom capacitive force sensor using fibre-chip coupling. JOURNAL OF MICROMECHANICS AND MICROENGINEERING , 10(4), 492-497.
Abstract: The design and fabrication of a novel multi-degree-of-freedom force sensor is described. The three-dimensional structure of the sensor is a result of combining several microfabrication techniques: wet bulk micromachining, fusion bonding, chemical mechanical polishing, deep RIE, LPCVD, PECVD and thermally evaporated thin films. The sensor is designed to operate in the 0-500 μN force range and the 0-10 μNm torque range. The flexibility of the process to create overhanging structures with arbitrary lengths and heights is illustrated by the integration of micro-tweezers directly onto the force sensor. Among other advantages of the developed process is a dicing-free self-release of wafer structures. This allows very fragile structures, such as micromirrors and other optical components, to be individually packaged.
Laveau, A., Kapat, J. S., Chow, L. C., Enikov, E., & Sundaram, K. B. (2000). Design, analysis and fabrication of a meso-scale centrifugal compressor. American Society of Mechanical Engineers, Advanced Energy Systems Division (Publication) AES , 40, 129-137.
Abstract: A gas or vapor compressor is one of the key components of many engineering systems, such as certain designs of vapor compression refrigeration systems, cryo-coolers, air handlers. For meso-scale systems with linear dimensions of a few centimeters, conventional designs do not work efficiently because of rather large relative tolerances, and hence these meso-scale systems require micro-fabricated components for efficient operation. This paper presents a meso-scale centrifugal compressor fabricated by photo-lithographic techniques. A preliminary design based on 1-D flow analysis using air as the working fluid shows that a 50 mm diameter centrifugal compressor with a blade height of 200 μm gives a static pressure ratio of 1.12. In this design, the impeller has 10 full blades and 10 splitter blades. Each blade has the NACA profile 9510 with the maximum camber at 50% of the chord. These impeller blades have exit angles 35° with exit flow angles of 60°. A vaned diffuser having 20 equally spaced vanes with the same NACA profile is used to improve compressor efficiency. A 3-D compressible, viscous flow analysis has been done using a commercial finite volume software. The results of this analysis allowed the verification of the flow characteristics inside the meso-scale centrifugal compressor. The compressor has been fabricated using micro-fabrication techniques. The rotor and the stator are made by etching a silicon wafer by using DRIE (Deep Reactive Ion Etching) technique. A Pyrex wafer is then bonded to the stator for visual access inside the compressor.
Oliver, D., & Enikov, R. (2000). Micro-particles temperature measurements in a plasma jet. VACUUM , 58(2-3), 244-249.
Enikov, E. T., & Boyd, J. G. (1999). A thermodynamic field theory for anodic bonding of micro electro-mechanical systems (MEMS). International Journal of Engineering Science , 38(2), 135-158.
Abstract: An anodic bond is modeled as a moving nonmaterial line forming the intersection of three material surfaces representing the unbonded conductor, the unbonded insulator, and the bonded interface. Global integral equations are written for the conservation of mass, momentum, and energy, Maxwell's equations, and the second law of thermodynamics. The global equations are then localized in the volume, the material surfaces, and the nonmaterial bond line. The second law is used to determine the thermodynamic conjugates in the thermodynamic potential and the dissipation inequality. It is demonstrated that the jump in the Poynting vector across a surface is equal to the surface Joule heating due to surface electric conduction currents. © 1999 Elsevier Science Ltd. All rights reserved.
Enikov, E. T., & Nelson, B. J. (1999). MEMS based single cell penetration force sensor. MICROROBOTICS AND MICROASSEMBLY , 3834, 40-46.
Enikov, E. T., & Nelson, B. J. (1999). MEMS based single cell penetration force sensor. Proceedings of SPIE - The International Society for Optical Engineering , 3834, 40-46.
Abstract: The rapid development of reproductive biology has created a need for quantifying penetration forces during artificial fertilization. It has been demonstrated that the success of such procedures heavily depends on the mechanics of penetration of the egg's zona and membrane. To quantify the forces during intracytoplasmic injections we have developed a MEMS based force sensor. Deep RIE and fusion bonding are used to fabricate a variable capacitance type sensor. It is designed to measure the penetration force during intracytoplasmic injection of egg cells as well as other applications in the 1-500 μmN force range. The sensor measures tri-axial forces using a system of flexible beams subjected to bending and torsion. The process is relatively simple and allows for easy modification of the force range. A penetration pipette tip is attached to the sensor body using a low temperature bonding technique. Calibration, sensitivity and initial experimental data is provided.
Enikov, E., & Stepan, G. (1998). Microchaotic motion of digitally controlled machines. JOURNAL OF VIBRATION AND CONTROL , 4(4), 427-443.
Enikov, E., & Stépán, G. (1998). Microchaotic motion of digitally controlled machines. JVC/Journal of Vibration and Control , 4(4), 427-443.
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.
Enikov, E., & Stepan, G. (1995). Micro-chaotic behavior of digitally controlled machines. American Society of Mechanical Engineers, Design Engineering Division (Publication) DE , 84(3 Pt A/1), 399-406.
Abstract: The desired stationary motions of machines are often unstable. Human operator or computer control may be needed to stabilize these machines. An important common feature of both analog and digital controllers, is the time delay which is introduced into the system. Even when these delayed systems should be stable, the experiments show small stochastic oscillations around the desired motion. 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 micro-chaos or μ-chaos.
VISSOKOV, G. P., STEFANOV, B. I., GERASIMOV, N. T., OLIVER, D. H., ENIKOV, R. Z., VRANTCHEV, A. I., BALABANOVA, E. G., & PIRGOV, P. S. (1988). PLASMACHEMICAL TECHNOLOGY FOR HIGH-DISPERSION PRODUCTS. JOURNAL OF MATERIALS SCIENCE , 23(7), 2415-2418.

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