Onur Ferhanoğlu

• Professor
• Associate Professor at Istanbul Technical University

We conducted a series of experimental investigations to generate laser-stimulated millimeter bubbles (MBs) around silver nanoparticles (AgNPs) and thoroughly examined the mechanism of bubble formation within this nanocomposite system. One crucial aspect we explored was the lifetime and kinetics of these bubbles, given that bubbles generated by plas...

Capsule endoscopy offers a non-invasive and patient-friendly method for imaging the gastrointestinal tract, boasting superior tissue accessibility compared to traditional endoscopy and colonoscopy. While advances have led to capsules capable of drug delivery, tactile sensing, and biopsy, size constraints often limit a single capsule from having mul...

We present the design and deployment of a capsule endoscope via external electromagnets for locomotion in large volumes alongside its digital twin implementation based on interval type-2 fuzzy logic systems (IT2-FLSs). To perform locomotion, we developed an external mechanism comprising five external electromagnets on a two-dimensional translationa...

We present and demonstrate a cascaded laser scan architecture to achieve a threefold gain in scan angle. We cascaded multiple piezoelectric MEMS scanners using a high numerical aperture relay lens pair in between scanners, which are located at optical conjugate planes. The cascaded scan architecture comprising 3 scanners is simulated using ray-trac...

We present a novel implantable MEMS sensor - readout glasses pair towards the real-time monitoring of intraocular pressure. The overall system comprises i) a diffraction grating interferometric MEMS sensor to be embedded in the cornea and ii) readout glasses embedded with a laser diode, miniaturized aspheric lenses, and a CMOS camera. Owing to the...

This study presents a novel in-situ Young’s modulus measurement technique of polydimethylsiloxane (PDMS) microfluidic chips that are designed to measure fluid viscosities. In such chips, viscosity can be accurately determined once the Young’s modulus of PDMS is also known. Yet, the Young’s modulus values of elastomers are highly dependent on their...

We present a compact electromagnetically actuated 3D-printed rotary actuator for use in Scanning Capsule Endoscopy. The actuator comprises two cantilevers connected to a rotating body via nylon strings. External coils and the magnets placed on the cantilevers create an electromagnetic force with which the rotation can be initiated. Opposite coils a...

We are pleased to provide readers with the newest and important technologies presented at the International Conference on Optical MEMS and Nanophotonics 2022 (OMN 2022), through this Special Issue published by the IEEE Photonics Technology Letters (PTL) journal. The Optical Micro- and Nano Systems (OMN) conferences have surged in prominence over th...

This paper presents the design, manufacturing, and characterization of a three-dimensional (3D)-printed and electromagnetically actuated adjustable optical slit structure. The device comprises magnet-attached slits connected to the main frame via two springs controlled by external coils. To analyze the forces acting on the springs and simulate the...

In this study, we investigate the effect of fused deposition modeling printing direction on the effective Young’s modulus value of cantilevers. Through finite-element simulations and experiments with seven different dimensions and totaling over 100 cantilevers, we have observed the impact of printing direction on cantilever resonance. Unlike the co...

We present a stacked temperature, pressure, and localization platform, targeted for minimally invasive surgical and diagnostic applications under Magnetic Resonance Imaging. The platform comprises a micro-fabricated three-layer (Titanium-Parylene-Titanium) membrane pressure sensor, a Gallium Arsenide band-gap temperature sensor, and a magnetic mate...

In this study, we showcase the design, manufacturing, and characterization of the focus adjustment actuator for use in capsule endoscopy. The actuator has a spiral flexure, carrying a lens and multiple magnets at its center to facilitate focusing through electromagnetic actuation. The interplay between the spiral flexure length and the lens size is...

In this study, the design of a direct down-conversion, double-balanced Gilbert Mixer at 432 MHz is presented. The proposed circuit achieves a 13.4 dB double-sideband noise figure with an associated flicker corner frequency of 250 kHz. The conversion gain of the mixer is approximately 10.2 dB, with an IIP3 of 8.2 dBm simulated in the post-layout set...

In this study, we present the design, implementation and demonstration of a 3D-printed actuator-based optical beam-steering technique to be utilized for an improved physical layer security in VLC applications with a comparably favorable secrecy capacity.

In this study, we design a pair of third‐order conformal Hilbert curve antennas for use in capsule endoscopy at three different bands (Industrial, Scientific, and Medical [ISM]), especially at 433 MHz, 915 MHz, and 2.45 GHz. The antennas are placed orthogonally with respect to each other, offering dual linear polarization characteristics, which hav...

In this study, we present the design, manufacture, and implementation of a 3D-printed lens scanner-based beam steering for use in visible light communication (VLC) applications. The ${{5}}\;{\rm{cm}} \times {{5}}\;{\rm{cm}}$ scanner is designed for low-cost 3D printing with fused deposition modeling using polylactic acid. Scanning is facilitated th...

We present a simple, low-cost and effective method to monitor mode-shapes of dynamic structures, based on laser triangulation. Through the smart adjustment of the camera view angle, we were able to acquire the mode-shapes on two orthogonal planes, without the need to change the placement of neither the device-under-test, nor the illumination or det...

We present a novel meandered dual loop conformal antenna operated at 433 MHz ISM band for wireless capsule endoscopy. The proposed antenna provides a wide bandwidth to tolerate the resonance frequency shifts due to tissue composition changes along with the capsule movement in the gastrointestinal (GI) tract and a wide axial ratio beamwidth to enabl...

We present the design and characterization of a 3D-printed spiral actuator towards focus adjustment in endoscopes. The actuator, holding an aspherical lens, can be electromagnetically actuated to achieve ~0.5 mm displacement at 10 mW power.

We present a low-cost and biocompatible 3D-printed fluidic device composed of a main body and two lids with membranes in between forming a tunable lens. The main body and the lids of the device is manufactured using stereolithography (SLA) technology and comprises of one or two inlets. Collagen type-I enriched Sodium Alginate membranes are sandwich...

PurposeCapsule endoscopy offers increased patient comfort and improved visibility of the entire gastrointestinal (GI) tract. Besides imaging, numerous literary studies on capsule endoscopy have demonstrated drug delivery, navigation strategies, tactile sensing for tumor diagnosis, and biopsy. Yet, the size limitation hampers the availability of mul...

Polarization properties of collagen in acidic and natural solutions were analyzed by a decoupling analytical technique based on Mueller matrix polarimetry (MMP). The proposed method was employed to derive five effective optical parameters of collagen solutions: (1) orientation angle of linear birefringence, (2) phase retardance of linear birefringe...

Applicability of the Mueller Matrix (MM) polarimetry for the optical characterization of the olive and sunflower oils were tested. For this aim, linear dichroism and optical rotation of circular birefringence of the oil samples divided into three comparable groups as pure olive oil (heated and non-heated), pure sunflower oil (heated and non-heated)...

Microsystems sensors are implemented on a fiber optics based platform towards use in magnetic resonance imaging assisted interventions. The presented platform offers real-time and in-situ pressure, temperature, and localization feedback during imaging assisted surgical procedures. This multi-sensor platform fits into an interventional medical devic...

A conventional secure visible light communication (VLC) system that is composed of one transmitter, one friendly jammer with multiple light-emitting-diodes, one legitimate receiver and one eavesdropper is considered. We propose the use of an optical lens at the legitimate transmitter as an additional effective and practical security measure. We inv...

Imaging of tissue sections at multiple depths with a miniaturized optical imaging probe necessitates 3D actuation capability. A number of MEMS studies in literature have addressed 3D actuation either through a single scanning unit with three degrees of freedom, or combination of multiple scanning units each having one or more degrees of freedom in...

Microbubbles and nanobubbles have several characteristics that are comparable with millimeter- and centimeter-sized bubbles. These characteristics are their small size, which results in large surface area and high bioactivity, low rising velocity, decreased friction drag, high internal pressure, large gas dissolution capacity, negatively charged su...

Higher-order Bessel-like optical beams can be created through off-axis coupling of light into a multimode fiber. Thanks to the aberration that is inherent in spherical surfaces, through directing the Bessel-like beam comprising multiple concentric rings onto a low-cost lens, we created multiple foci at different depths. Moreover, scanning of the op...

Bu çalı¸smada kapsül endoskopi uygulamalarında kullanılmak üzere 400 MHz frekansında konformal yapıda döngü anten tasarlanmı¸s ve gerçeklenmi¸stir. Tasarlanan antenin performansı, kapsülün hareketi boyunca bulunacagı sindirim sistemi ˘ organları için ayrıca test edilmi¸stir. Tasarlanan antenin gerçeklenmesi için kapsül üç boyutlu yazıcı ile bastırı...

In this paper, we aimed to investigate the reliability of an organic light-emitting diode (OLED) and propose a SPICE compatible electrical model for automotive exterior lighting applications. The proposed model smoothly provides the forward and reverse current-voltage relation and also dynamic capacitive behavior of OLED is included in the model. T...

Visible light communication (VLC) is a promising technique to provide connectivity to users while providing illumination. To further improve the data rates of VLC systems, multiple sources that transmit multiple simultaneous data streams can be used. This Letter proposes a novel mixture model for VLC systems that make use of multiple sources to pro...

Side viewing, miniaturized laser scanning endoscopes are powerful tools in providing sub-cellular level resolution and multi-layered imaging of the walls of body cavities. Yet, the level of miniaturization for such devices is significantly hampered by the necessity for 45° placement of the whole scanner unit with respect to the cavity axis. With it...

We present an optical efficiency improved speckle spectrometer where a scattering metal wave-guide is utilized along with a conventional prism spectrometer. We conducted extensive tests on 25 different scatterers, involving a variety of nanoparticle concentrations, scattering layer thicknesses, and wave-guide vs. non-guiding type scatterers. We obs...

3D printing is a rapidly emerging low-cost, high-yield, and high-speed manufacturing technique that has already been utilized in fabricating sensor and actuator devices. Here we investigate the cyclic fatigue and the effect of heating on 10 x 10 mm2-sized, 3D-printed polyamide-based laser scanning electromagnetic actuators, which are intended for i...

We present a design approach consisting of one-dimensional photonic crystal filters for Laser Scanning Microscopy (LSM) applications. The proposed approach based on Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method provides significant flexibility in modeling desired transmission band while offering widened stop-bands. Strict spec...

Precise investigation of the temperature and the duration for collagen denaturation is critical for a number of applications, such as adjustment of temperature and duration during a laser assisted tissue welding or collagen based tissue repair products (films, implants, cross linkers) preparation procedures. The result of such studies can serve as...

This paper summarizes the design, fabrication, and characterization of a magnetically actuated stainless-steel based micro-scanner. The out-of-plane deflection of the proposed device is calculated by using a custom depth scan setup. The main advantage of laser cutting technology, which is utilized in manufacturing the proposed steel scanner, is its...

We present a mode-optimized two-dimensional piezoelectric fiber actuator and a robust actuation scheme to establish three different scan patterns with the same device. Having multiple scan options, the operator of the actuator is free to choose between improved uniformity, high frame rate to image abrupt biological event, or circular field-of-view...

A micro-scanner made of stainless-steel is fabricated via laser cutting technology for 3D Lissajous confocal imaging. The multi-gimbaled structure of the device provides two orthogonal torsional modes and three different out-of-plane modes. Torsional modes can be used to achieve 2D scan and all of the out-of-plane modes can be used in changing the...

We present a novel spectrometer device, offering a wide wavelength range and high resolution. The device builds upon a conventional prism spectrometer; however, an additional scattering medium is introduced to generate a wavelengthdependent speckle pattern on the detector array. Simultaneous use of the prism and the scattering medium allows for bot...

Recent advances in the field of stereolithography based manufacturing, have led to a number of 3D-printed sensor and actuator devices, as a cost-effective and low fabrication complexity alternative to micro-electro-mechanical counterparts. Yet the reliability of such 3D-printed dynamic structures have yet to be explored. Here we perform reliability...

In this study, we propose a compact, lightweight scanning fiber microdisplay towards virtual and augmented reality applications. Our design that is tailored as a head-worn-display simply consists of a four-quadrant piezoelectric tube actuator through which a fiber optics cable is extended and actuated, and a reflective (or semi-reflective) ellipsoi...

We present a disposable miniaturized confocal imager, consisting mostly of three-dimensional (3-D)-printed components. A 3-D printed laser scanner with 10×10 mm² frame size is employed for Lissajous scan, with 180 and 315 Hz frequencies in orthogonal directions corresponding to ±8 deg and ±4 deg optical scan angles, respectively. The actuation is d...

A piezo-scanning fiber endoscopic device architecture is proposed for 3D imaging or ablation. The endoscopic device consists of a piezoelectric membrane that is placed perpendicular to the optical axis, a fiber optic cable that extends out from and actuated by the piezoelectric membrane, and one or multiple lenses for beam delivery and collection....

Piezoelectric actuated fiber-scanners have often been employed in optical imaging of tissues, owing to their compact size, low cost, high resolution that is accompanied by high framerates. Typically having a circular cross-section, the dynamics of the scan pattern is determined by the fiber geometry and material properties. Having circular symmetry...

A stainless-steel based micro-scanner with magnetic actuation is fabricated via laser-cutting technology targeted for confocal microscopy. Laser cutting offers low-cost and high speed fabrication of such scanners. The device is designed to establish a 2D Lissajous pattern. For a coil drive of 180 mA, fabricated scanner is able to deliver 4 degrees...

In this study, the design, fabrication, and characterization results of square and circular cross-sectioned, bimaterial microelectromechanical system (MEMS) membranes are presented. The MEMS structures, having width of 250 μm to 1.5 mm and 1-4 mm² die area, were designed towards integration on a single-mode fiber tip for temperature-sensing. Embedd...

We present the development of a 5 mm, piezo-actuated, ultrafast laser scalpel for fast tissue microsurgery. Delivery of micro-Joules level energies to the tissue was made possible by a large, 31 μm, air-cored inhibited-coupling Kagome fiber. We overcome the fiber’s low NA by using lenses made of high refractive index ZnS, which produced an optimal...

A two-dimensional (2D) polymer based scanning mirror with magnetic actuation is developed for imaging applications. Proposed device consists of a circular suspension holding a rectangular mirror and can generate a 2D scan pattern. Three dimensional (3D) printing technology which is used for implementation of the device, offers added flexibility in...

We propose a novel fiber sensor utilizing a thermomechanical MEMS element at the fiber tip. Owing to its Parylene/Titanium bimaterial structure, the MEMS membrane exhibits an out-of plane displacement with changing temperature. Together with the MEMS element, the embedded diffraction grating forms an in-line interferometer, from which the displacem...

This letter demonstrates a novel prism-based optical-readout, which uses a single prism to detect the incoming TM polarized wave just below the critical angle. The method is used with a 35-μm-pixel pitch MEMS thermal sensor, whose inclination angle changes with the absorbed infrared (IR) radiation that results in an increase in the reflectivity at...

This paper demonstrates a 35-µm pixel pitch MEMS thermal sensor array with optical-readout. We implemented an AC-coupled readout method for a single MEMS pixel using a photodetector, which responds only to changes in the scene. AC-coupled readout substantially reduced the optical noise by eliminating the large DC beam. This method can be scaled to...

A thermo-mechanical MEMS detector with 35-μm pixel pitch is designed, fabricated, and characterized. This fabricated design has one of the smallest pixel sizes among the IR thermo-mechanical MEMS sensors in the literature. The working principle of the MEMS detector is based on the bimaterial effect that creates a deflection when exposed to IR radia...

We propose a novel fiber sensor utilizing a thermomechanical MEMS element at the fiber tip. Owing to its Parylene/Titanium bimaterial structure, the MEMS membrane exhibits an out-of-plane displacement with changing temperature. Together with the MEMS element, the embedded diffraction grating forms an in-line interferometer, from which the displacem...

We proposed a novel two-wavelength optical readout for grating based thermo-mechanical MEMS arrays by using two color LEDS butt-coupled to a multi-mode fiber, which provides spatial auto-registration of two different color images on a single camera. The −1st diffraction orders of the different colors are simultaneously monitored with different chan...

Towards developing precise microsurgery tools for the clinic, we previously developed image-guided miniaturized devices using low repetition rate amplified ultrafast lasers for surgery. To improve the speed of tissue removal while reducing device diameter, here we present a new 5-mm diameter device that delivers high-repetition rate laser pulses fo...

Vocal fold scarring is one of the major cause of voice disorders yet there is no reliable treatment. We hypothesized to solve this problem by creating sub-epithelial voids to localize biomaterials to restore the pliability of scarred vocal folds. In order to guide this precise surgery, there is a need for performing deep tissue imaging. Here, we pr...

A lead for an electronic device which resists the induction of a current from an electromagnetic field external to said lead includes one or more pairs of adjacent segments of electrical wire, each of the pairs including a first segment of electrical wire and a second segment of electrical wire. The lead also includes one or more shielded RF chokes...

Multiphoton fluorescence microscopy (MPM) is a method for high resolution, non-invasive investigations of biological tissue. The aim of introducing an annular shaped laser beam is to reduce the ouf-of-focus generated background signal improving imaging of light scattering tissue such as human skin. Simulations show that 50% of the beam radius can b...

Ultrafast pulsed lasers can be used to achieve remarkable precision during surgical ablation. Through nonlinear interactions with tissue, ultrafast lasers can provide a largely non-thermal mechanism of ablation and a unique ability to create targeted damage within bulk tissue. These advantages have made ultrafast lasers the ideal surgical tool for...

Toward developing a new method for restoring tissue viscoelasticity in scarred vocal folds, we previously proposed a method to localize biomaterials within subepithelial voids ablated using ultrafast laser pulses. The clinical implementation of this method necessitates the quantification of the laser parameters for ablating scarred tissue. Here, we...

Vocal fold scarring is one of the major causes of voice disorders and may arise from overuse or post-surgical wound healing. One promising treatment utilizes the injection of soft biomaterials aimed at restoring viscoelasticity of the outermost vibratory layer of the vocal fold, superficial lamina propria (SLP). However, the density of the tissue a...

The thermal sensor system presented in this paper is based on the mechanical bending due to the incident IR radiation. A diffraction grating is embedded under each pixel to facilitate optical readout. Typically the first diffraction order is used to monitor the sub-micron mechanical displacement with sub-nanometer precision. In this work; two diffe...

We present a 9.6-mm fiber-coupled probe for femtosecond laser microsurgery and nonlinear imaging. Towards enabling clinical use, we successfully reduced the volume of our earlier 18-mm surgery probe by 5 times, while improving optical performance.

Diffraction gratings integrated with microelectromechanical systems (MEMS) sensors offer displacement measurements with subnanometer sensitivity. However, the sensitivity of the interferometric readout may drop significantly based on the gap between the grating and the reference surface. A two- wavelength ( 2 − λ ) readout method was previously tes...

Dynamic diffraction gratings can be microfabricated with precision and offer extremely sensitive displacement measurements and light intensity modulation. The effect of pure translation of the moving part of the grating on diffracted order intensities is well known. This study focuses on the parameters that limit the intensity and the contrast of t...

We present the optical design of a 9.6-mm diameter fiber-coupled probe for combined femtosecond laser microsurgery and nonlinear optical imaging. Towards enabling clinical use, we successfully reduced the dimensions of our earlier 18-mm microsurgery probe by half, while improving optical performance. We use analytical and computational models to op...

Diffraction gratings integrated with MEMS sensors offer sensitive displacement measurements. However, the sensitivity of the interferometric readout may drop significantly based on the sensor position. A two wavelength readout method was developed and tested previously in order to maintain the sensitivity of the readout > %50 maximum sensitivity ov...

Thermo-mechanical detector arrays in the 160 × 120 array format are designed, fabricated, and tested. Detectors are composed of SiNx and TiN as absorbing layer, Al to form bimaterial legs, and integrated diffraction grating interferometer underneath each detector. The detector array is a passive component and the optical readout is performed remote...

Microfabricated Lamellar grating interferometers (LGI) require fewer components compared to Michelson interferotemeters and offer compact and broadband Fourier transform spectrometers (FTS) with good spectral resolution, high speed and high efficiency. This study presents the fundamental equations that govern the performance and limitations of LGI...

A miniaturized and electromagnetically driven FR4 based moving platform is developed for Fourier Transform spectrometer applications. Both Michelson interferometer and Lamellar Grating interferometer configurations are demonstrated. plusmn500 mum translational motion (corresponding to 5 cm^-1 spectral resolution) is demonstrated with the...

Lamellar grating interferometers (LGI) offer compact spectrometer architecture with high spectral resolution and large clear aperture. This study investigates the diffraction based inherent limitations of LGI spectrometers in contrary to conventional Michelson type spectrometer architecture. Simulations and experiments were conducted to demonstrate...