Browsing by Author "Puttlitz, C."
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Item Open Access Bio-implantable passive on-chip RF-MEMS strain sensing resonators for orthopaedic applications(Institute of Physics Publishing Ltd., 2008) Melik, R.; Perkgoz, N. K.; Unal, E.; Puttlitz, C.; Demir, Hilmi VolkanOne out of ten bone fractures does not heal properly due to improper load distribution and strain profiles during the healing process. To provide implantable tools for the assessment of bone fractures, we have designed novel, bio-implantable, passive, on-chip, RF-MEMS strain sensors that rely on the resonance frequency shift with mechanical deformation. For this purpose, we modeled, fabricated and experimentally characterized two on-chip sensors with high quality factors for in vivo implantation. One of the sensors has an area of ∼0.12 mm2 with a quality factor of ∼60 and the other has an area of ∼0.07 mm2 with a quality factor of ∼70. To monitor the mechanical deformation by measuring the change in the resonance frequencies with the applied load, we employed a controllable, point load applying experimental setup designed and constructed for in vitro characterization. In the case of the sensor with the larger area, when we apply a load of 3920 N, we obtain a frequency shift of ∼330 MHz and a quality factor of ∼76. For the smaller sensor, the frequency shift and the quality factor are increased to 360 MHz and 95, respectively. These data demonstrate that our sensor chips have the capacity to withstand relatively high physiologic loads, and that the concomitant and very large resonant frequency shift with the applied load is achieved while maintaining a high signal quality factor. These experiments demonstrate that these novel sensors have the capacity for producing high sensitivity strain readout, even when the total device area is considerably small. Also, we have demonstrated that our bio-implantable, passive sensors deliver a telemetric, real-time readout of the strain on a chip. Placing two more resonators on the sides of the sensor to serve as transmitter and receiver antennas, we achieved to transfer contactless power and read out loads in the absence of direct wiring to the sensor. With this model, where telemetric measurements become simpler due to the fact that all sensor system is built on the same chip, we obtain a frequency shift of ∼190 MHz with an increase in the quality factor from ∼38 to ∼46 when a load of 3920 N is applied. Therefore, as a first proof of concept, we have demonstrated the feasibility of our on-chip strain sensors for monitoring the mechanical deformation using telemetry-based systems.Item Open Access Circular high-Q resonating isotropic strain sensors with large shift of resonance frequency under stress(2009) Melik, R.; Unal, E.; Perkgoz, N.K.; Puttlitz, C.; Demir, Hilmi VolkanWe present circular architecture bioimplant strain sensors that facilitate a strong resonance frequency shift with mechanical deformation. The clinical application area of these sensors is for in vivo assessment of bone fractures. Using a rectangular geometry, we obtain a resonance shift of 330 MHz for a single device and 170 MHz for its triplet configuration (with three side-by-side resonators on chip) under an applied load of 3,920 N. Using the same device parameters with a circular isotropic architecture, we achieve a resonance frequency shift of 500 MHz for the single device and 260 MHz for its triplet configuration, demonstrating substantially increased sensitivity. © 2009 by the authors.Item Open Access Flexible metamaterials for wireless strain sensing(American Institute of Physics, 2009-11-04) Melik, R.; Unal, E.; Perkgoz, N. K.; Puttlitz, C.; Demir, Hilmi VolkanWe proposed and demonstrated flexible metamaterial-based wireless strain sensors that include arrays of split ring resonators (SRRs) to telemetrically measure strain. For these metamaterial sensors, we showed that a flexible substrate (e.g., Kapton tape) delivers greater sensitivity and a more linear response as compared to using silicon substrates. Specifically, these tape-based flexible SRR sensors exhibit a significantly improved sensitivity level of 0.292 MHz/kgf with a substantially reduced nonlinearity error of 3% for externally applied mechanical loads up to 250 kgf. These data represent a sixfold increase in sensitivity and a 16-fold reduction in error percentage.Item Open Access Metamaterial based telemetric strain sensing in different materials(Optical Society of American (OSA), 2010) Melik, R.; Unal, E.; Perkgoz, N.K.; Puttlitz, C.; Demir, Hilmi VolkanWe present telemetric sensing of surface strains on different industrial materials using split-ring-resonator based metamaterials. For wireless strain sensing, we utilize metamaterial array architectures for high sensitivity and low nonlinearity-errors in strain sensing. In this work, telemetric strain measurements in three test materials of cast polyamide, derlin and polyamide are performed by observing operating frequency shift under mechanical deformation and these data are compared with commercially-available wired strain gauges. We demonstrate that hard material (cast polyamide) showed low slope in frequency shift vs. applied load (corresponding to high Young's modulus), while soft material (polyamide) exhibited high slope (low Young's modulus).Item Open Access Metamaterial-based wireless RF-MEMS strain sensors(IEEE, 2010) Melik, Rohat; Ünal, Emre; Perkgoz, Nihan Kosku; Puttlitz, C.; Demir, Hilmi VolkanApproximately 10% of the fractures do not heal properly because of the inability to monitor fracture healing. Standard radiography is not capable of discriminating whether bone healing is occurring normally or aberrantly. We propose and develop an implantable wireless sensor that monitors strain on implanted hardware in real time telemetrically. This enables clinicians to monitor fracture healing. Here we present the development and demonstration of metamaterial-based radiofrequency (RF) micro-electro-mechanical system (MEMS) strain sensors for wireless strain sensing to monitor fracture healing. The operating frequency of these sensors shifts under mechanical loading; this shift is related to the surface strain of the implantable test material. In this work, we implemented metamaterials in two different architectures as bio-implantable wireless strain sensors for the first time. These custom-design metamaterials exhibit better performance as sensors than traditional RF structures (e.g., spiral coils) because of their unique structural properties (splits). They feature a low enough operating frequency to avoid the background absorption of soft tissue and yield higher Q-factors compared to the spiral structures (because their gaps have much higher electric field density). In our first metamaterial architecture of an 5x5 array, the wireless sensor shows high sensitivity (109kHz/kgf, 5.148kHz/microstrain) with low nonlinearity-error (<200microstrain). Using our second architecture, we then improved the structure of classical metamaterial and obtained nested metamaterials that incorporate multiple metamaterials in a compact nested structure and measured strain telemetrically at low operating frequencies. This novel nested metamaterial structure outperformed classical metamaterial structure as wireless strain sensors. By employing nested metamaterial architecture, the operating frequency is reduced from 529.8 MHz to 506.2 MHz while the sensitivity is increased from 0.72 kHz/kgf to 1.09 kHz/kgf. ©2010 IEEE.Item Open Access Metamaterial-based wireless strain sensors(American Institute of Physics, 2009-07-07) Melik, R.; Unal, E.; Perkgoz, N. K.; Puttlitz, C.; Demir, Hilmi VolkanWe proposed and demonstrated metamaterial-based strain sensors that are highly sensitive to mechanical deformation. Their resonance frequency shift is correlated with the surface strain of our test material and the strain data are reported telemetrically. These metamaterial sensors are better than traditional radio-frequency (rf) structures in sensing for providing resonances with high quality factors and large transmission dips. Using split ring resonators (SRRs), we achieve lower resonance frequencies per unit area compared to other rf structures, allowing for bioimplant sensing in soft tissue (e.g., fracture healing). In 5×5 SRR architecture, our wireless sensors yield high sensitivity (109 kHz/kgf, or 5.148 kHz/microstrain) with low nonlinearity error (<200 microstrain).Item Open Access Nested metamaterials for wireless strain sensing(IEEE, 2009-12-28) Melik, R.; Unal, E.; Perkgoz, N. K.; Santoni, B.; Kamstock, D.; Puttlitz, C.; Demir, Hilmi VolkanWe designed, fabricated, and characterized metamaterial-based RF-microelectromechanical system (RF-MEMS) strain sensors that incorporate multiple split ring resonators (SRRs) in a compact nested architecture to measure strain telemetrically. We also showed biocompatibility of these strain sensors in an animal model. With these devices, our bioimplantable wireless metamaterial sensors are intended, to enable clinicians, to quantitatively evaluate the progression of long-bone fracture healing by monitoring the strain on the implantable fracture fixation hardware in real time. In operation, the transmission spectrum of the metamaterial sensor attached to the implantable fixture is changed when an external load is applied to the fixture, and from this change, the strain is recorded remotely. By employing telemetric characterizations, we reduced the operating frequency and enhanced the sensitivity of our novel nested SRR architecture compared to the conventional SRR structure. The nested SRR structure exhibited a higher sensitivity of 1.09 kHz/kgf operating at lower frequency compared to the classical SRR that demonstrated a sensitivity of 0.72 kHz/kgf. Using soft tissue medium, we achieved the best sensitivity level of 4.00 kHz/kgf with our nested SRR sensor. Ultimately, the laboratory characterization and in vivo biocompatibility studies support further development and characterization of a fracture healing system based on implantable nested SRR.Item Open Access A novel bio-microelectromechanical system for in vivo diagnostic monitoring of facture healing(ASME, 2013) McGilvray, K.; Demir, Hilmi Volkan; Ünal, Emre; Puttlitz, C.Item Open Access RF-MEMS load sensors with enhanced Q-factor and sensitivity in a suspended architecture(Elsevier, 2010-11-09) Melik, R.; Unal, E.; Perkgoz, N. K.; Puttlitz, C.; Demir, Hilmi VolkanIn this paper, we present and demonstrate RF-MEMS load sensors designed and fabricated in a suspended architecture that increases their quality-factor (Q-factor), accompanied with an increased resonance frequency shift under load. The suspended architecture is obtained by removing silicon under the sensor. We compare two sensors that consist of 195 μm × 195 μm resonators, where all of the resonator features are of equal dimensions, but one's substrate is partially removed (suspended architecture) and the other's is not (planar architecture). The single suspended device has a resonance of 15.18 GHz with 102.06 Q-factor whereas the single planar device has the resonance at 15.01 GHz and an associated Q-factor of 93.81. For the single planar device, we measured a resonance frequency shift of 430 MHz with 3920 N of applied load, while we achieved a 780 MHz frequency shift in the single suspended device. In the planar triplet configuration (with three devices placed side by side on the same chip, with the two outmost ones serving as the receiver and the transmitter), we observed a 220 MHz frequency shift with 3920 N of applied load while we obtained a 340 MHz frequency shift in the suspended triplet device with 3920 N load applied. Thus, the single planar device exhibited a sensitivity level of 0.1097 MHz/N while the single suspended device led to an improved sensitivity of 0.1990 MHz/N. Similarly, with the planar triplet device having a sensitivity of 0.0561 MHz/N, the suspended triplet device yielded an enhanced sensitivity of 0.0867 MHz/N.Item Open Access Utilizing multiple bioMEMS sensors to monitor orthopaedic strain and predict bone fracture healing(Wiley Periodicals, Inc., 2019) Wolynski, J.; Sutherland, C.; Demir, Hilmi Volkan; Ünal, Emre; Alipour, A.; Puttlitz, C.; McGilvray, K.Current diagnostic modalities, such as radiographs or computed tomography, exhibit limited ability to predict the outcome of bone fracture healing. Failed fracture healing after orthopaedic surgical treatments are typically treated by secondary surgery; however, the negative correlation of time between primary and secondary surgeries with resultant health outcome and medical cost accumulation drives the need for improved diagnostic tools. This study describes the simultaneous use of multiple (n = 5) implantable flexible substrate wireless microelectromechanical (fsBioMEMS) sensors adhered to an intramedullary nail (IMN) to quantify the biomechanical environment along the length of fracture fixation hardware during simulated healing in ex vivo ovine tibiae. This study further describes the development of an antenna array for interrogation of five fsBioMEMS sensors simultaneously, and quantifies the ability of these sensors to transmit signal through overlaying soft tissues. The ex vivo data indicated significant differences associated with sensor location on the IMN (p < 0.01) and fracture state (p < 0.01). These data indicate that the fsBioMEMS sensor can serve as a tool to diagnose the current state of fracture healing, and further supports the use of the fsBioMEMS as a means to predict fracture healing due to the known existence of latency between changes in fracture site material properties and radiographic changes. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1873–1880, 2019