F.L. Degertekin

Georgia Institute of Technology, Atlanta, Georgia, United States

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Publications (218)264.64 Total impact

  • Toby Xu, Coskun Tekes, F Degertekin
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    ABSTRACT: Use of high-κ dielectric, atomic layer deposition (ALD) materials as an insulation layer material for capacitive micromachined ultrasonic transducers (CMUTs) is investigated. The effect of insulation layer material and thickness on CMUT performance is evaluated using a simple parallel plate model. The model shows that both high dielectric constant and the electrical breakdown strength are important for the dielectric material, and significant performance improvement can be achieved, especially as the vacuum gap thickness is reduced. In particular, ALD hafnium oxide (HfO2) is evaluated and used as an improvement over plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (Six)Ny)) for CMUTs fabricated by a low-temperature, complementary metal oxide semiconductor transistor-compatible, sacrificial release method. Relevant properties of ALD HfO2) such as dielectric constant and breakdown strength are characterized to further guide CMUT design. Experiments are performed on parallel fabricated test CMUTs with 50-nm gap and 16.5-MHz center frequency to measure and compare pressure output and receive sensitivity for 200-nm PECVD Six)Ny) and 100-nm HfO2) insulation layers. Results for this particular design show a 6-dB improvement in receiver output with the collapse voltage reduced by one-half; while in transmit mode, half the input voltage is needed to achieve the same maximum output pressure.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control. 12/2014; 61(12):2121-31.
  • Karim G Sabra, Justin Romberg, Shane Lani, F Levent Degertekin
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    ABSTRACT: Monolithic integration of capacitive micromachined ultrasonic transducer arrays with low noise complementary metal oxide semiconductor electronics minimizes interconnect parasitics thus allowing the measurement of thermal-mechanical (TM) noise. This enables passive ultrasonics based on cross-correlations of diffuse TM noise to extract coherent ultrasonic waves propagating between receivers. However, synchronous recording of high-frequency TM noise puts stringent requirements on the analog to digital converter's sampling rate. To alleviate this restriction, high-frequency TM noise cross-correlations (12-25 MHz) were estimated instead using compressed measurements of TM noise which could be digitized at a sampling frequency lower than the Nyquist frequency.
    The Journal of the Acoustical Society of America 06/2014; 135(6):EL364. · 1.65 Impact Factor
  • F. L. Degertekin, C. Tekes, T. Xu, S. Satir, G. Gurun, J. Zahorian
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    ABSTRACT: Although catheter based intravascular ultrasound (IVUS) imaging of arterial cross sections and intracardiac echography (ICE) imaging of the heart in two dimensions have proven to be very useful in many interventional procedures used in the diagnosis and treatment of coronary and structural heart diseases, extension of these techniques to three-dimensional (3-D) volumetric imaging will have a dramatic impact. Truly volumetric images in front of an IVUS catheter will enable accurate evaluation and safer crossing of chronic total occlusions (CTOs) in coronary and peripheral arteries. Three dimensional ICE imaging in the heart can improve the outcome of challenging procedures such as trans-catheter valve replacements by providing the clinicians exceptional capability for real-time spatial mapping. These imaging devices would be enabled by miniature ultrasound systems that can be placed at the tip of mechanically flexible catheters. We have been developing technologies for integration of capacitive micromachined ultrasonic transducer (CMUT) arrays and custom designed CMOS front end electronics on the same silicon chip for ultimately miniaturized ultrasound systems for 3-D IVUS and ICE imaging. To implement these CMUT-on-CMOS systems, we post-process CMOS wafers to fabricate CMUTs using a low temperature process [1]. The CMOS electronics are designed specifically for low noise operation with CMUTs and use smart power management to reduce the power consumption, and time division multiplexing to reduce the cable count in the catheter to about 10 for an imaging array with over 100 elements [2]. With this approach, a 300um thick, 1-2mm diameter donut shaped silicon contains most of the required front end functionality, resulting in very flexible 3-7F catheters for 3-D IVUS and ICE imaging applications. Figure 1 shows a CMUT-on-CMOS chip with 1.4-mm-diameter dual-ring CMUT array on a front-end IC implemented in 0.35-µm CMOS process after silicon donut shaping using deep reactive ion etching (left) and after initial flex tape electrical connections (right). The dual-ring array has 56 transmit elements and 48 receive elements on two separate concentric annular rings. The IC incorporates a 25-V pulser for each transmitter element and a low-noise transimpedance amplifier (TIA) for each receiver, along with digital control. The final shape of the silicon chip is a 1.5-mm-diameter donut with a 430-µm center hole for a guide wire. The overall front-end system requires only 13 external connections and provides 4 parallel RF outputs while consuming an average power of 20-mW. The frequency of operation is around 20-MHz, suitable for forward looking volumetric IVUS imaging of CTOs. This device has been tested on wire phantoms and ex vivo chicken heart samples to demonstrate its capability to collect 3-D ultrasound imaging data at 60 fr/s rate and dynamic range comparable to commercial IVUS systems [3]. In addition to providing details of this type of CMUT-on-CMOS systems, we will discuss the use of this approach for implementing MRI compatible intracardiac imaging catheters as well as integration of an IVUS imaging system on a 0.014” diameter guidewire. * J. Zahorian, M. Hoffman, T. Xu, G. Gurun, S. Satir, M. Karaman, and F.L. Degertekin “Monolithic CMUT on CMOS Integration for Intravascular Ultrasound Applications,” IEEE Trans. on UFFC, vol. 58, pp. 2659-2667, 2011. * G. Gurun, P. Hasler, and F.L. Degertekin, “Frontend Receiver Electronics for High Frequency Monolithic CMUT-on-CMOS Imaging Arrays,” IEEE Trans. on UFFC, vol. 58, 1658-1668, 2011. * G. Gurun, C. Tekes, J. Zahorian, T. Xu, S. Satir, M. Karaman and F.L. Degertekin, “Single-Chip CMUT-on-CMOS front-end System for Real Time Volumetric IVUS and ICE Imaging,” IEEE Trans. on UFFC, to appear in February 2014.
    225th ECS Meeting; 05/2014
  • Shane Lani, Karim G Sabra, F Levent Degertekin
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    ABSTRACT: Subwavelength focusing and imaging has been a long sought after goal and one that metamaterials can possibly achieve. In 2011, Lemoult et al. used time reversal techniques to focus sound to as small as λ/25 in air by using the evanescent wave field above a gird of soda cans acting as Helmholtz resonators [Lemoult et al. Phys. Rev. Lett. 107, 064301, (2011)]. This paper will demonstrate subwavelength focusing in immersion in the 11-0 MHz frequency range with capacitive micromachined ultrasonic transducer (CMUT) arrays. CMUTs are microscale (10-100 μm wide) membrane arrays, which support evanescent surface waves that derive their dispersive properties not only from the periodic structure of the array, but also from the membrane resonance. Furthermore, CMUTs have embedded electrodes for electrostatic excitation and detection of acoustic waves which allow implementation of time reversal techniques to focus the dispersive evanescent surface waves using only the CMUTs on the same substrate as sources and receivers. Using a finite boundary element method simulation, we demonstrate subwavelength focusing at points in the near-field above a 2D CMUT array in immersion.
    The Journal of the Acoustical Society of America 04/2014; 135(4):2222. · 1.65 Impact Factor
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    ABSTRACT: A lattice Boltzmann (LB) formulation, which is consistent with the phase-field model for two-phase incompressible fluid, is proposed to model the interface dynamics of droplet impingement. The interparticle force is derived by comparing the macroscopic transport equations recovered from LB equations with the governing equations of the continuous phase-field model. The inconsistency between the existing LB implementations and the phase-field model in calculating the relaxation time at the phase interface is identified and an approximation is proposed to ensure the consistency with the phase-field model. It is also shown that the commonly used equilibrium velocity boundary for the binary fluid LB scheme does not conserve momentum at the wall boundary and a modified scheme is developed to ensure the momentum conservation at the boundary. In addition, a geometric formulation of the wetting boundary condition is proposed to replace the popular surface energy formulation and results show that the geometric approach enforces the prescribed contact angle better than the surface energy formulation in both static and dynamic wetting. The proposed LB formulation is applied to simulating droplet impingement dynamics in three dimensions and results are compared to those obtained with the continuous phase-field model, the LB simulations reported in the literature, and experimental data from the literature. The results show that the proposed LB simulation approach yields not only a significant speed improvement over the phase-field model in simulating droplet impingement dynamics on a submillimeter length scale, but also better accuracy than both the phase-field model and the previously reported LB techniques when compared to experimental data. Upon validation, the proposed LB modeling methodology is applied to the study of multiple-droplet impingement and interactions in three dimensions, which demonstrates its powerful capability of simulating extremely complex interface phenomena.
    Physical Review E 03/2014; 89(3-1):033311. · 2.31 Impact Factor
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    ABSTRACT: Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range.
    Applied Physics Letters 02/2014; 104(5):051914. · 3.52 Impact Factor
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    ABSTRACT: Intravascular ultrasound (IVUS) and intracardiac echography (ICE) catheters with real-time volumetric ultrasound imaging capability can provide unique benefits to many interventional procedures used in the diagnosis and treatment of coronary and structural heart diseases. Integration of capacitive micromachined ultrasonic transducer (CMUT) arrays with front-end electronics in single-chip configuration allows for implementation of such catheter probes with reduced interconnect complexity, miniaturization, and high mechanical flexibility. We implemented a single-chip forward-looking (FL) ultrasound imaging system by fabricating a 1.4-mm-diameter dual-ring CMUT array using CMUT-on-CMOS technology on a front-end IC implemented in 0.35-μm CMOS process. The dual-ring array has 56 transmit elements and 48 receive elements on two separate concentric annular rings. The IC incorporates a 25-V pulser for each transmitter and a low-noise capacitive transimpedance amplifier (TIA) for each receiver, along with digital control and smart power management. The final shape of the silicon chip is a 1.5-mm-diameter donut with a 430-μm center hole for a guide wire. The overall front-end system requires only 13 external connections and provides 4 parallel RF outputs while consuming an average power of 20 mW. We measured RF A-scans from the integrated single- chip array which show full functionality at 20.1 MHz with 43% fractional bandwidth. We also tested and demonstrated the image quality of the system on a wire phantom and an ex vivo chicken heart sample. The measured axial and lateral point resolutions are 92 μm and 251 μm, respectively. We successfully acquired volumetric imaging data from the ex vivo chicken heart at 60 frames per second without any signal averaging. These demonstrative results indicate that single-chip CMUT-on-CMOS systems have the potential to produce realtime volumetric images with image quality and speed suitable for catheter-based clinical applications.
    IEEE transactions on ultrasonics, ferroelectrics, and frequency control 02/2014; 61(2):239-50. · 1.80 Impact Factor
  • S Tol, FL Degertekin, A Erturk
    SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring; 01/2014
  • Shane Lani, M Wasequr Rashid, Karim G Sabra, F Levent Degertekin
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    ABSTRACT: Capacitive micromachined ultrasonic transducer (CMUT) arrays are made up of microscale (10-100[micro sign]m wide) membranes with embedded electrodes for electrostatic excitation and detection of acoustic waves. While typically used for far-field imaging, CMUT arrays also support dispersive evanescent surface waves. These surface waves derive their dispersive properties not only from the periodic structure of the array, but also from the membrane resonance. One advantage of CMUTs as a metamaterial is that the dispersive qualities of the array can be tuned by changing the applied bias voltage to the membranes, which in effect changes the membrane stiffness. A second advantage is that the CMUT array elements can be used as receivers to record the acoustic waves with high spatial resolution, which make laser displacement measurement based characterization unnecessary. These properties allow the possibility of CMUTs to exploit these slowly propagating evanescent waves as a means for creating subwavelength resolution fields for high-resolution ultrasound imaging and sensing in the near field by appropriately tuning the physical characteristics of individual membranes. The dispersive behavior of these evanescent surface waves propagating along a CMUT array was quantified using a computationally efficient, boundary element method based model and validated with both finite element analysis and experimental data obtained from a 1 x 16 CMUT array with a membrane resonance tunable between 5 and 6.5 MHz.
    The Journal of the Acoustical Society of America 11/2013; 134(5):4102. · 1.65 Impact Factor
  • D Torello, F Levent Degertekin
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    ABSTRACT: A new method of actuating atomic force microscopy (AFM) cantilevers is proposed in which a high frequency (>5 MHz) wave modulated by a lower frequency (∼300 kHz) wave passes through a contact acoustic nonlinearity at the contact interface between the actuator and the cantilever chip. The nonlinearity converts the high frequency, modulated signal to a low frequency drive signal suitable for actuation of tapping-mode AFM probes. The higher harmonic content of this signal is filtered out mechanically by the cantilever transfer function, providing for clean output. A custom probe holder was designed and constructed using rapid prototyping technologies and off-the-shelf components and was interfaced with an Asylum Research MFP-3D AFM, which was then used to evaluate the performance characteristics with respect to standard hardware and linear actuation techniques. Using a carrier frequency of 14.19 MHz, it was observed that the cantilever output was cleaner with this actuation technique and added no significant noise to the system. This setup, without any optimization, was determined to have an actuation bandwidth on the order of 10 MHz, suitable for high speed imaging applications. Using this method, an image was taken that demonstrates the viability of the technique and is compared favorably to images taken with a standard AFM setup.
    The Review of scientific instruments 11/2013; 84(11):113705. · 1.52 Impact Factor
  • Sarp Satir, Jaime Zahorian, F. Levent Degertekin
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    ABSTRACT: A large-signal, transient model has been developed to predict the output characteristics of a CMUT array operated in the non-collapse mode. The model is based on separation of the nonlinear electrostatic voltage-to-force relation and the linear acoustic array response. For modeling of linear acoustic radiation and crosstalk effects, the boundary element method is used. The stiffness matrix in the vibroacoustics calculations is obtained using static finite element analysis of a single membrane which can have arbitrary geometry and boundary conditions. A lumped modeling approach is used to reduce the order of the system for modeling the transient nonlinear electrostatic actuation. To accurately capture the dynamics of the non-uniform electrostatic force distribution over the CMUT electrode during large deflections, the membrane electrode is divided into patches shaped to match higher order membrane modes, each introducing a variable to the system model. This reduced order nonlinear lumped model is solved in the time domain using commercial software. The model has two linear blocks to calculate the displacement profile of the electrode patches and the output pressure for a given force distribution over the array. The force-to-array-displacement block uses the linear acoustic model, and the Rayleigh integral is evaluated to calculate the pressure at any field point. Using the model, the time-domain transmitted pressure can be simulated for different large drive signal configurations. The acoustic model is verified by comparison to harmonic FEA in vacuum and fluid for high- and low-aspect-ratio membranes as well as mass-loaded membranes. The overall software model is verified by comparison to transient 3-D finite element analysis and experimental results for different large drive signals, and an example for a phased array simulation is given.
    IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 11/2013; 60(11):2426-2439. · 1.82 Impact Factor
  • Serife Tol, F. Levent Degertekin, Alper Erturk
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    ABSTRACT: Vibration-to-electricity conversion has been heavily researched over the last decade with the ultimate goal of enabling self-powered small electronic components to use in wireless applications ranging from medical implants to structural health monitoring sensors. Regardless of the transduction mechanism used in transforming vibrational energy into electricity, the existing research efforts have mostly focused on deterministic or stochastic harvesting of direct vibrational energy available at a fixed location in space. Such an approach is convenient to design and employ linear and nonlinear vibration-based energy harvesters, such as base-excited cantilevers with piezoelectric laminates. Although the harvesting of local vibrations using linear and nonlinear devices has been well studied, there has been little effort to investigate power extraction from elastic waves propagating in host structures to gain a fundamental understanding of power flow and to best exploit not only standing but also traveling wave energy. This paper explores the problem of piezoelectric energy harvesting from one-dimensional bending waves involving propagating and evanescent components with a focus on infinitely long thin beams. A pair of electroded piezoelectric patches is implemented as the energy harvesting interface connected to a complex electrical load. An analytical modeling framework is given in order to relate the harvested power to incoming wave in the presence of a generalized resistive-reactive circuit. Effects of energy harvesting on the global wave dynamics as well as individual propagating and evanescent wave components are investigated with an emphasis on the wavelength matching concept. The electrical loading conditions for maximum power and efficiency are identified for several special cases in the low frequency range.
    ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems; 09/2013
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    ABSTRACT: A shape coefficient is introduced to quantify droplet shape by measuring its similarity to a desired shape to enable the study of droplet shape evolution upon impingement on a solid surface. Parametric simulations are performed with an experimentally validated numerical model to determine the impact conditions to maximize the shape coefficient. Results show that the Weber number is the controlling factor that determines the maximum achievable shape coefficient and the time instant when it is achieved for small Ohnesorge numbers, whereas the Reynolds number becomes the key parameter defining the optimal shape when the Ohnesorge number is large. A regime map is also developed to define the regions where a desired droplet shape can be achieved without splash. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3071–3082, 2013
    AIChE Journal 08/2013; 59(8). · 2.58 Impact Factor
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    ABSTRACT: High frequency ultrasound arrays have applications ranging from imaging of small animals, skin and eye to intravascular ultrasound (IVUS). We describe an application where a guidewire IVUS system uses high frequency phased arrays with integrated electronics placed directly on the guidewire rather than a catheter for imaging. Multiple arrays provide the full transverse cross section of the artery during percutaneous interventions. We focus on a 1-D CMUT phased array to be used in the guidewire IVUS. CMUTs are particularly suitable for this application with their ease of fabrication and single chip electronics integration. The array frequency is chosen to be around 35-40MHz with 10MHz bandwidth so that the 1-D CMUT phased array with a 300um wide aperture can closely match the lateral resolution of a current 20MHz, 3.5F solid state IVUS array. Here we discuss the initial design, large signal modeling, fabrication and experimental characterization of a 12 element, 300×1000um CMUT array with 25um pitch. The electrical and acoustic characterization results for a CMUT array with 20um square membranes are presented. Modeling results for different size membranes indicating adequate performance for higher bandwidth applications are also discussed.
    2013 IEEE International Ultrasonics Symposium (IUS); 07/2013
  • Sarp Satir, Toby Xu, F. Levent Degertekin
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    ABSTRACT: A model based transmit optimization method for Capacitive Micromachined Ultrasonic Transducer (CMUT) arrays operated in conventional imaging mode is presented. For the large signal analysis we used the transient CMUT array model presented in [1]. As an example, a 15 MHz, 60% FBW CMUT array element with 16 membranes and 70 nm gap is modeled, fabricated and tested. Through, fast iterative simulations, the transmit behavior of the transducer for the full range of different drive signals is explored as a function of DC bias, pulse width, and amplitude for unipolar and bipolar pulsed operation. It is shown that for a CMUT element operating in the non-collapse mode, the absolute maximum possible pressure output is generated when the transducer is driven with no DC bias and a very short unipolar pulse that results in full gap swing. By adjusting pulse width and amplitude, full gap swing can be achieved with small peak pulse voltages, maximizing the transmit sensitivity in Pa/V. In all cases, maximum achievable pressure is about 2 dB of the absolute maximum. The case where the TX and RX elements are the same is also investigated where the 95% of the collapse voltage is applied to the transmitting element for optimal receive sensitivity. In this case, a bipolar pulse is applied. The first part of the pulse adds to the DC bias force to pull the membrane down near the full gap and the second part effectively removes DC bias, releasing the membrane to achieve largest swing past its rest position. With this strategy, absolute maximum pressure can also be achieved with large DC bias levels.
    2013 IEEE International Ultrasonics Symposium (IUS); 07/2013
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    ABSTRACT: Effective intracellular delivery is a significant impediment to research and therapeutic applications at all processing scales. Physical delivery methods have long demonstrated the ability to deliver cargo molecules directly to the cytoplasm or nucleus, and the mechanisms underlying the most common approaches (microinjection, electroporation, and sonoporation) have been extensively investigated. In this review, we discuss established approaches, as well as emerging techniques (magnetofection, optoinjection, and combined modalities). In addition to operating principles and implementation strategies, we address applicability and limitations of various in vitro, ex vivo, and in vivo platforms. Importantly, we perform critical assessments regarding (1) treatment efficacy with diverse cell types and delivered cargo molecules, (2) suitability to different processing scales (from single cell to large populations), (3) suitability for automation/integration with existing workflows, and (4) multiplexing potential and flexibility/adaptability to enable rapid changeover between treatments of varied cell types. Existing techniques typically fall short in one or more of these criteria; however, introduction of micro-/nanotechnology concepts, as well as synergistic coupling of complementary method(s), can improve performance and applicability of a particular approach, overcoming barriers to practical implementation. For this reason, we emphasize these strategies in examining recent advances in development of delivery systems.
    Journal of the Association for Laboratory Automation 06/2013; · 1.46 Impact Factor
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    ABSTRACT: We designed and fabricated a dynamic receive beamformer integrated circuit (IC) in 0.35-μm CMOS technology. This beamformer IC is suitable for integration with an annular array transducer for high-frequency (30-50 MHz) intravascular ultrasound (IVUS) imaging. The beamformer IC consists of receive preamplifiers, an analog dynamic delay-and-sum beamformer, and buffers for 8 receive channels. To form an analog dynamic delay line we designed an analog delay cell based on the current-mode first-order all-pass filter topology, as the basic building block. To increase the bandwidth of the delay cell, we explored an enhancement technique on the current mirrors. This technique improved the overall bandwidth of the delay line by a factor of 6. Each delay cell consumes 2.1-mW of power and is capable of generating a tunable time delay between 1.75 ns to 2.5 ns. We successfully integrated the fabricated beamformer IC with an 8-element annular array. Experimental test results demonstrated the desired buffering, preamplification and delaying capabilities of the beamformer.
    IEEE Transactions on Biomedical Circuits and Systems 10/2012; 6(5):454-67. · 2.74 Impact Factor
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    ABSTRACT: The impact of droplets onto a substrate in ink-jet printing is critical for control and optimization of the droplet deposition process to improve part quality and accuracy and to reduce the manufacturing time. However, most previous research on droplet impingement dynamics mainly utilized one metric — the droplet spreading radius, which does not provide enough information for manufacturing purposes. This paper presents a new metric that is relevant to manufacturing by characterizing the droplet shape by measuring the similarity between the droplet shape and a desired shape over time. This enables a model of droplet shape evolution and optimization of the droplet deposition process to build desired geometries. Meanwhile, analyses with this shape metric aids understanding the physics of droplet shape evolution during impingement. A 2-D shape metric is first proposed and test cases are given to validate the effectiveness of the shape metric. Then the definition is extended to characterize 3-D droplet shape. Results also show the 3-D shape metric is effective and robust.
    ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference; 08/2012
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    ABSTRACT: An intravascular ultrasound (IVUS) catheter that can provide forward viewing volumetric ultrasound images would be an invaluable clinical tool for guiding interventions. Single chip integration of front-end electronics with capacitive micromachined ultrasonic transducers (CMUTs) is highly desirable to reduce the interconnection complexity and enable miniaturization in IVUS catheters. For this purpose we use the monolithic CMUT-on-CMOS integration where CMUTs are fabricated directly on top of pre-processed CMOS wafers. This minimizes parasitic capacitances associated with connection lines. We have recently implemented a system design including all the required electronics using 0.35-µm CMOS process integrated with a 1.4-mm diameter CMUT array. In this study, we present the experimental volumetric imaging results from an ex-vivo chicken heart phantom. The imaging results demonstrate that the single-chip forward looking IVUS (FL-IVUS) system with monolithically integrated electronics has potential to visualize the front view of coronary arteries.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:3195-8.
  • Source
    Hamdi Torun, Ofer Finkler, F Levent Degertekin
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    ABSTRACT: The authors describe a method for biomolecular force clamp measurements using atomic force microscope (AFM) cantilevers and micromachined membrane-based electrostatic actuators. The actuators comprise of Parylene membranes with embedded side actuation electrodes and are fabricated on a silicon substrate. The devices have a displacement range of 1.8μm with 200V actuation voltage, and displacement uncertainty is 0.8nm, including the noise and drift. The settling time, limited by the particular amplifier is 5ms, with an inherent range down to 20μs. A force clamp measurement setup using these actuators in a feedback loop has been used to measure bond life-times between human IgG and anti-human IgG molecules to demonstrate the feasibility of this method for biological experiments. The experimental findings are compared with a molecular pulling experiment and the results are found to be in good agreement.
    Ultramicroscopy 07/2012; 122C:26-31. · 2.47 Impact Factor

Publication Stats

2k Citations
264.64 Total Impact Points

Institutions

  • 2000–2014
    • Georgia Institute of Technology
      • • School of Mechanical Engineering
      • • School of Electrical & Computer Engineering
      • • School of Chemistry and Biochemistry
      Atlanta, Georgia, United States
    • The International Society for Optics and Photonics
      International Falls, Minnesota, United States
  • 2011–2012
    • Bogazici University
      • Department of Electrical and Electronic Engineering
      İstanbul, Istanbul, Turkey
    • Bahçeşehir University
      İstanbul, Istanbul, Turkey
  • 2009–2011
    • Isik University
      İstanbul, Istanbul, Turkey
    • University of South Florida
      Tampa, Florida, United States
  • 2006–2008
    • Sandia National Laboratories
      Albuquerque, New Mexico, United States
  • 1993–2001
    • Stanford University
      • Department of Electrical Engineering
      Stanford, CA, United States
  • 1998
    • Bilkent University
      • Department of Electrical & Electronic Engineering
      Ankara, Ankara, Turkey
  • 1994
    • Texas Instruments Inc.
      Dallas, Texas, United States