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Breast cancer is one of the most challenging health problems in women worldwide. Early detection and regular breast cancer screening can considerably improve the survival rate. Many advanced imaging technologies are currently being used in the detection of breast malignancy. However, these methods are costly, uncomfortable, and time-consuming. Therefore, in this work, a simple and noninvasive thermographic technique, based on a Fiber Bragg Grating (FBG) thermal sensor array, has been developed to detect breast cancer. Breast tissue is simulated using agar gel phantom, and the heaters are embedded inside the phantom in different locations to mimic the tumors. FBG thermal sensor array is employed to acquire the surface temperature distribution of the simulated breast phantom. Also, modeling of the tissue-mimicking phantom and tumor in COMSOL Multiphysics software is carried out to provide a detailed 3D thermal view of the proposed prototype. Both experimental and simulated results are found to be in agreement and display the same trend as expected. Experimental results show that a temperature variation of ≥0.3°C is detected at the location of the tumor’s presence, which can be easily picked up by FBG interrogators which have sensitivity of ~1 pm, indicating the efficacy of the proposed sensing prototype as a potential screening tool for the diagnosis of breast cancer.

In recent years, numerous measurement techniques have been employed to characterize surface textures in the micrometer and nanometer range. Although these techniques have enabled significant advances in surface metrology, larger surface details are not easily measurable with such techniques. We propose a simple and reliable fiber Bragg grating (FBG) based tactile displacement sensor to measure a wide range of displacements that vary from $0.2~\mu \text{m}$ to 2mm. The device adopts a novel multi-pivot mechanical lever-based amplification mechanism to achieve a wide measurement range. Experimental results show that the sensor can measure both 219nm thick, thin-film coating and 1.22mm glass slide by selecting an appropriate pivot position. Further, the device is employed to identify topographies of three different surfaces of different dimensions. The sensor’s optimized configuration demonstrates an excellent displacement sensitivity of 63926pm/mm with a high resolution of 15.64nm. The repeatability of the sensor in this configuration is 2.44%.

The real-time, continuous, beat-to-beat blood pressure (BP) monitoring is vital in clinical scenarios such as operations theatres, ambulances etc. In the present study, a non-invasive BP monitoring methodology based on Fiber Bragg Grating sensors is reported. The design and development of Fiber Bragg Grating based Pulse Monitoring Device (FBGPM) is demonstrated which is capable of acquiring the radial arterial pulse pressure waveform effectively in real time. The Radial Arterial Pulse Pressure Waveform is acquired on beat to beat basis employing developed FBGPM in a clinical environment. Further, the recorded radial arterial pulse pressure waveform is processed to obtain systolic and diastolic BP by utilizing a standard non-invasive BP measurement device as a reference. The BP values obtained through FBGPM are then compared with the BP values obtained through an Intra-Arterial (IA) probe. The FBGPM is a chemically and electrically inert device which makes it an effective candidate for monitoring the real-time BP. The focus of the study is to demonstrate the feasibility of deploying developed FBGPM device in clinical environment to acquire beat-to-beat BP and subsequently compare the present device to the IA probe method of BP acquisition.

In this paper, we report on the comprehensive study on Molybdenum disulfide (MoS2) nanolayer coated etched Fiber Bragg Grating (eFBG) strain sensor. MoS2 nanolayer is coated using Physical Vapor Deposition (PVD) of Molybdenum (Mo) on eFBGs followed by sulfurization of the same in an inert atmosphere at 450° C. Such coating technique provides a direct control over the coating thickness of MoS2, thereby enabling a study based on the effect of nanolayer coating thickness on the intrinsic strain sensitivity as well as the power of the back reflected Bragg wavelength of eFBG in the 0.78eV spectral region. High uniformity of MoS2 nanolayer coating ensures consistent, repeatable and highly linear FBG strain sensors with a correlation coefficient of 0.988 in the range of 0 to $2500~\mu \varepsilon $ . A maximum intrinsic strain sensitivity of ~6.65 pm/ $\mu \varepsilon $ with a resolution of $\sim 150~\text{n}\varepsilon $ have been achieved with optimized MoS2 coated eFBG sensors. This kind of consistent, highly sensitive and linear strain sensors when incorporated with proper packaging schemes can be particularly useful for applications demanding high sensitivity of FBG sensors such detection of seismic vibrations, underwater acoustic signals, low amplitude accelerations, etc.

Gait analysis is vital from the view of its established capacity as an indicator for neuromuscular disorders. Gait analysis is carried out in order to provide a quantified assessment of human movement which may aid orthopaedic and podiatric fraternity to suggest suitable therapeutic treatment. The proposed study comprises of two wearable non-invasive devices realized using FBG sensors i.e. Knee Angle Measurement Device (KAMD) for dynamic knee angle measurement and Forefoot Load Measurement Device (FLMD) for dynamic measurement of load on the forefoot. In the present study, the assessment of locomotion is illustrated and analyzed utilizing the developed devices without any time synchronization complexity. During locomotion, the swing and the stance phase is analyzed with respect to both knee joint angle and forefoot load which further reveals the complementary nature between them. In addition, FLMD can also be utilized for the evaluation of single and double limb support phases during locomotion. Furthermore, the novel cantilever approach utilized in the FLMD design ensures to acquire the load imparted specifically over the forefoot region which facilitates FLMD to be employed for assessment of other locomotory actions such as landing phase analysis during leaps, climbing stairs, treadmill tests etc. Also, the cantilever approach helps minimize the hysteresis effects on the device.

To understand the electrical switching behavior of Si15Te $_{85-{x}}$ Cu x ( $1\le {x} \le10$ ) series, ${I}$ – ${V}$ characterization has been performed on bulk as well as amorphous thin films of the as-prepared samples. Both the bulk glasses and amorphous thin films are found to manifest memory-type switching behavior. The threshold voltages of thin-film devices are found to be much lower than the bulk counterparts and hence could find application for phase change memory (PCM). The composition analyses of both have divulged the existence of intermediate phase (IP) in the composition range of $2 \le {x} \le6$ . To examine the probability of the given glass for PCM application, Set–Reset studies have been performed on the glasses with a triangular pulse of 6 mA for set operation and rectangular pulse of 12 mA for the reset operation. The study has revealed a continuous repetition of few Set–Reset cycle by the Si–Te–Cu series. Raman studies carried out on the bulk glasses report the occurrence of blue shift over the composition in a regular manner. Further, SEM studies have been carried out on Si–Te–Cu samples to understand the morphological changes that would have occurred during switching. Additionally, thickness dependence of threshold voltage of representative Si15Te80Cu5 and Si15Te76Cu9 glasses has been carried out to reveal the relationship between threshold voltage and thickness.

The detection and quantification of DNA is of critical importance in various molecular biology processes and has applications in fields ranging from forensics to environmental monitoring. Here, the development of a highly sensitive and label-free technique for DNA detection is reported. This article proposes a reduced graphene oxide (rGO) coated etched Fiber Bragg Grating (eFBG) sensor as a tool for the detection and quantification of dsDNA. The proposed sensor is found to have a limit of detection of 261.87 pg/ $\mu \text{l}$ and the sensor response is a linear function of the dsDNA concentration in the range between 1 ng/ $\mu \text{l}$ to 50 ng/ $\mu \text{l}$ with excellent stability and repeatability. The paper also proposes a technique to quantitatively measure the amount of DNA bound to the sensor and thus, the DNA binding efficacy of the rGO coating on the sensor, utilizing UV spectrometry.

Content delivery networks (CDNs) distribute much of the Internet content by caching and serving the objects requested by users. A major goal of a CDN is to maximize the hit rates of its caches, thereby enabling faster content downloads to the users. Content caching involves two components: an admission algorithm to decide whether to cache an object and an eviction algorithm to determine which object to evict from the cache when it is full. In this paper, we focus on cache admission and propose a novel algorithm called RL-Cache that uses model-free reinforcement learning (RL) to decide whether or not to admit a requested object into the CDN’s cache. Unlike prior approaches that use a small set of criteria for decision making, RL-Cache weights a large set of features that include the object size, recency, and frequency of access. We develop a publicly available implementation of RL-Cache and perform an evaluation using production traces for the image, video, and web traffic classes from Akamai’s CDN. The evaluation shows that RL-Cache improves the hit rate in comparison with the state of the art and imposes only a modest resource overhead on the CDN servers. Further, RL-Cache is robust enough that it can be trained in one location and executed on request traces of the same or different traffic classes in other locations of the same geographic region. The paper also reports extensive analyses of the RL-Cache sensitivity to its features and hyperparameter values. The analyses validate the made design choices and reveal interesting insights into the RL-Cache behavior. pub

We propose a simple and novel circular diaphragm-micro-stylus based single fiber Bragg grating (FBG) tactile sensor for reading Standard English Grade-1 Braille cells. The surface protrusions on the cells are transduced into strain variations on the FBG sensor, bonded along the line of symmetry of the diaphragm, by a free, vertically moving Micro-Stylus (MS). The tension mode of the diaphragm and the mass of the micro-styli are varied to optimize the sensing properties of the system. The maximum sensitivity of 1.786nm/mm is exhibited by the sensor system with the highest mass of the MS (MS-1; 167mg) in the highest tension mode (770μe). The repeatability error and resolution of the sensor in the aforementioned configurations are found to be 0.028nm and 559nm respectively. The proposed sensor system displayed good linearity, repeatability, high resolution, and easily adjustable sensitivity in the present scenario.

Finger plethysmography is a well-known technique for the acquisition of arterial pulse waveforms in the field of cardiology. The technique involves the acquisition of the volumetric variation of the finger due to pulsatile flow of blood in ulnar artery, to obtain the arterial pulse waveform of the subject. Conventionally, finger plethysmography is carried out by pulse-oximetry method which evaluates the blood flow using the oxygen saturation levels in blood. Though this method is widely used, the data acquired from this method is not the actual pulse pressure experienced by the arterial walls. Therefore, in the present work, a novel, non-invasive Fiber Bragg Grating based arterial pulse acquisition device employing finger Plethysmographic technique is designed and developed. The developed Fiber Bragg Grating Plethysmographic Pulse Recorder (FBGPPR) can acquire the volumetric variations of the finger on a beat-to-beat basis, which represents the arterial pulse waveform. Further, Pulse Transit Time (PTT) evaluation is also illustrated employing FBGPPR and an electronic stethoscope wherein both the devices are triggered simultaneously. Furthermore, the acquired pulse waveforms are analyzed to obtain the accelerated pulse plethysmograph (APG) which is noteworthy to observe the minute inflections and vital features of the pulse waveform.

Thermal imaging is one of the emerging non-invasive neuro-imaging techniques utilized for demarcation of intra-axial brain tumor borders. Tissue regions comprising of tumors is known to attain higher temperature on the surface due to the increased rate of blood flow and cell metabolism and therefore the variation in tissue surface temperature may be accounted as an indicator of a tumor existence. In the present work, Fiber Bragg Grating based Thermal Sensor (FBGTS) is developed for temperature measurement of a simulated tissue based on Agar material which mimics the soft tissue of brain. A heater is embedded inside the simulated tissue which mimics the tumor’s temperature variation inside the brain. The temperature of the embedded heater along with the surface temperature of the simulated tissue is acquired simultaneously using two FBGTS probes. Further, the temperature variations on the surface of the simulated tissue are studied for varying heater temperatures as well as for the varying position of the heater inside the simulated tissue, indicating varying positions of brain tumors. The present study proposes and demonstrates the feasibility of using FBGTS for thermography from which the possible detection and approximate position of an existing brain tumor can be evaluated.

This letter presents an improved fiber Bragg grating (FBG) displacement sensor for long-range measurements. A mechanical transfer structure is designed and developed, which converts the displacement of a measurement wire to the elastic deflection of a sensing arm. The wavelength shift difference between two FBGs symmetrically pasted on the sensing arm is found to be proportional to the displacement. The experimental results show that this design has a displacement sensitivity of 23.80 pm/mm within a measurement range of 0–150 mm. This improved displacement sensor shows good temperature compensation with the very low temperature sensitivity of 0.076 pm/°C for a temperature range of −40–120 °C. This sensor can be utilized for long-range and high endurance displacement measurement applications in harsh industrial environment.

Optical accelerometers, especially the fiber Bragg grating accelerometers are the preferred sensors for vibration, and acceleration measurement in several fields of engineering. They are light, compact, immune to electromagnetic interference, and provide better noise immunity due to wavelength encoded nature of signal transduction. In the present work, analytical modeling, numerical simulation, fabrication, and characterization of a novel double-L cantilever based fiber Bragg grating accelerometer is presented. This design not only enhances the sensitivity in comparison to its single-L counterpart, but also provides self-temperature compensation. Modular design of the accelerometer provides flexibility in replacing specific components to achieve desired performance characteristics. Resonant frequency of 86 Hz, sensitivity of 406.7 pm/g with an excellent linearity of 99.86 %, and small temperature sensitivity of 0.016 pm/°C have been demonstrated for the fabricated model. The FBG accelerometer has a linear operating range of ±6 g.

Fiber Bragg Grating-based accelerometers are being used in structural health monitoring as they offer several advantages over their electrical counterparts. In this paper, the concept of a novel T-shaped cantilever-based mechanical sensor head is proposed on which the two Fiber Bragg Gratings are integrated in a differential sensing configuration to realize an optical accelerometer. This elegant design simultaneously achieves the dual goals of sensitivity enhancement, and self-temperature compensation. A mathematical model of the accelerometer is developed, and numerical simulations are carried out for three mechanical sensor head designs. A prototype is fabricated and characterized to prove the design. The sensitivity of 821 pm/g of is achieved with a linearity of 99.7%, cross-axis sensitivity of 0.3%, and natural frequency of 64 Hz; self-temperature compensation is achieved with an error of 0.07 pm/°C.

Amorphous Ge15Te80– x In5Ag x ( $6\le {x} \le24$ ) thin films prepared in sandwich geometry exhibit memory switching behavior unlike the bulk sample that has shown both threshold switching for less current (1–2 mA) and memory switching for current greater than 2 mA. As anticipated, the threshold voltage of Ge15Te80– x In5Ag x ( $6\le {x} \le24$ ) thin films is found to be lower as contrast to those of bulk counterparts. The compositional dependence of amorphous system shows an extensive plateau in the range of $\textsf {6} \le {x} \le \textsf {12}$ which literally stands for the intermediate phase after which there is a drastic increase in the threshold field. Shifted rigidity percolation threshold has also been confirmed from the compositional dependence of threshold field of amorphous Ge15Te80– x In5Ag x thin films. In addition, the optical bandgap of a-Ge15Te80– x In5Ag x thin-film sample has been reckoned considering absorption spectra, and the compositional dependence has been described based on average bond energy of the system.

Human joint kinematics has established its capacity as a vital tool for joint pathology and gait analysis. Range of motion (ROM) of a knee joint performed by flexion and extension is an essential tool to assess the efficacy of surgical interventions or therapeutic assessment. This paper proposes a novel wearable device for dynamic measurement of knee joint angle using fiber Bragg grating (FBG) sensor. The proposed knee angle measurement device (KAMD) can transduce the angular movement between the shin and the thigh into strain variations on a cantilever, which is acquired by the FBG sensor over it. The KAMD is also facilitated with tuneable sensitivity with three modes of high sensitivity mode, medium sensitivity mode, and low sensitivity mode, which can be opted based on application specific resolution and range of measurement. The ROM data obtained from the KAMD are validated against ROM obtained from commercially available Polhemus Sensors. Furthermore, the synchronization of the knee joint movement of both legs during walking along with stance and swing phase is illustrated, which shows the ability of KAMD to perform gait analysis. Employment of KAMDs on both legs eliminating the time synchronization complexity makes the proposed FBG-based KAMD an efficient means to evaluate the knee angle from both legs simultaneously.

The deployment of the spinal needle of an appropriate gauge is highly essential in order to significantly reduce the side effects of lumbar puncture procedures performed for spinal anaesthesia and spinal surgeries. The gauge of the spinal needle used for the procedure plays a significant role in determining the force required for its insertion into the tissue and is chosen by the medical practitioner performing the procedure based on the expertise. The selection of the optimum gauge of the needle is subjective to the level of discretion exercised by the surgeon. This paper shows a comparative analysis of the force required for lumbar puncture with various tissue layers traversal by four different gauges of the spinal needle, making use of a real time dynamic force monitoring device which employs a fiber Bragg grating sensor. The fiber Bragg grating (FBG) force device (FBGFD) is used to measure the force variations on different gauges of spinal needle during the lumbar puncture procedure performed first on a simulator model and subsequently on a human cadaver specimen. The FBGFD facilitates dynamic measurement of force variation on the spinal needle during the penetration by the sensing bar mechanism which is acquired by the FBG sensor bonded over it with a resolution of 0.021 N. This comparative study of force may serve as a guideline for selection of proper gauge spinal needle during tissue puncture procedures minimizing post puncture effects on patients.

Goniometers are extensively used in the medical field, in order to assess the range of angular motion of a joint, especially for therapeutic assessment during physiotherapy. This paper reports a novel device for the dynamic measurement of angular motion of joints using a fiber Bragg grating (FBG) senor. The fiber Bragg grating goniometer (FBGG) is proposed, essentially converts the rotational motion of a joint into strain variation on a cantilever, which is acquired by the FBG sensor bonded over it. The FBGG developed has the capability of measuring joint angles in the range of 0°–200° with a resolution of 0.06°. The FBGG developed has been put to use in the measurement of angular motion of elbow joint along with ankle joint. The angular measurements obtained from the FBGG are validated against the angular measurements from the Polhemus liberty sensor. It is observed that the angular motions acquired from both the methodologies are in good agreement with each other, which proves the usefulness of the FBGG developed. Also, with the inherent advantages of the FBG sensor, the FBGG developed provides an efficient means of evaluation of angular motion of joint, which may be utilized as a platform sensor methodology for angular measurement of various other joints in the human body.

Under-bump metallization R c is a critical metric for high-density interconnect in electronic devices. We developed a test vehicle to characterize the impact of unit processes on R c for 10- $\mu \text{m}$ polymer passivation opening. We demonstrate that advanced preclean is necessary to achieve low (R c $\text{m}\Omega$ ) for future node extendibility, owing to reduction of both Al oxide and organometallic formation. This is achievable through a combination of low-temperature ( c performance. Influence of SiN etch on R c is also investigated, and it was found that Cl-chemistry is better than F-chemistry to achieve low R c .

Typical modern communication systems operate over a wide dynamic range of signal strengths. We consider the approach of adding a bias as offset to reduce switching activity, and study the average bit toggle for signals with different distributions, as a function of signal span and the actual bias value added. From the analysis, we provide guidelines to choose an optimal bias value, based on the system scenario, to obtain the lowest power consumption. Simulation results confirm the accuracy of the theoretical analysis. Various finite-impulse response filter architectures are evaluated, and we propose suitable enhancements to them to enable improved power savings. We apply the bias addition technique and the proposed architectural enhancements to a wireless local area network digital receiver chain, and demonstrate that over 25% power savings can be achieved under different signal conditions.

In this paper, we present the fabrication and characterization of molybdenum microheaters for high-temperature gas sensing applications. The surface morphology of dc magnetron sputtered molybdenum thin films was characterized by scanning electron microscopy and atomic force microscopy. The suspended membrane microheater consumed 104 mW to reach a maximum temperature of 800 degrees C and showed an absolute thermal resistance of 7.2 degrees C/mW. Thermal distribution patterns over the active heating area were recorded using FLIR camera. It showed a temperature gradient of 1.18 % from the center of the microheater to its periphery. The thermal and mechanical stabilities of the microheater were analyzed, and its membrane failure at higher operating temperatures was prevented. The microheater membrane deformation at different temperatures was characterized using optical profilometer, and its maximum value was found to be 16.25 mu m at 800 degrees C. The microheater response to a pulse, continuous pulse train, and constant dc voltages was characterized. Its response and recovery times are in the order of 19 and 34 ms, respectively. It showed a stable temperature with a negligible resistance drift (0.96%) over a period of 600 h. The TiO2 thin film integrated molybdenum microhotplate-based MEMS gas sensor response for CO (5000 ppb) was measured at different operating temperatures (300 degrees C-700 degrees C).

Pulmonary function tests (PFTs) are noninvasive diagnostic tests that evaluate the functionality of the lungs. Spirometry is an established diagnostic tool for the evaluation and management of lung disorders. Pulmonary function testing carried out using a spirometer provides vital information about the functional status of the respiratory system. In this study, a spirometer based on a fiber Bragg grating (FBG) sensor for PFT has been proposed. The proposed fiber Bragg grating spirometer (FBGS) is a novel, noninvasive device that has the ability to convert the rate of air flow into strain variations using an FBG sensor bonded on a cantilever. The FBGS dynamically acquires in real time, the complete breath sequence comprising of inhalation phase, pause phase, and exhalation phase, in terms of the air flow rate along with the time duration of each phase. Fundamental pulmonary parameters such as forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), the FEV1/FVC ratio, and peak expiratory flow are evaluated from the data obtained from the FBGS, which will aid greatly during clinical tests. The results from the FBGS developed are compared with a standard hospital grade pneumotachograph-based spirometer for a sample size of 16 subjects to prove the efficacy of the proposed device.

Power densities required to operate active-matrix organic-light-emitting diode (AMOLED) based displays for high luminance applications, lead to temperature rise due to self heating. Temperature rise leads to significant degradation and consequent reduction in life time. In this work numerical techniques based computational fluid dynamics (CFD) is used to determine the temperature rise and its distribution for an AMOLED based display for a given power density and size. Passive cooling option in form of protruded rectangular fins is implemented to reduce the display temperature.

In recent years, DNA-templated copper nanoparticles have been used to detect several important analytes, primarily through fluorescence spectrometry. However, the fluorescence of these nanoparticles decays within a few minutes making the quantitative estimation of analytes difficult. Despite the loss of fluorescence, the nanoparticles remain intact as evidenced by microscopy techniques like TEM and AFM. Here, etched fibre Bragg Grating (eFBG) sensors are presented as a detection/characterization tool for copper nanoparticles templated by double stranded DNA. The proposed sensor has a sensitivity of 1.5395 nm/RIU and a resolution of 0.00612 RIU. The formation of the copper nanoparticles on the DNA template attached to the eFBG sensor leads to a significant shift of ≈ 58 pm in the reflected Bragg wavelength signal. Further, the application of the proposed eFBG sensors for analyte detection utilizing the interruption in the synthesis of copper nanoparticles is demonstrated here with the example of melamine detection. The Bragg wavelength shift varies linearly with the log concentration of melamine ( ${R}^{2}=0.9482$ ) and the sensor can detect up to 0.1 ppm of melamine.

The out-diffusion of germanium from the core of a photosensitive fiber under elevated temperature is exploited to form a FabryProt filter within a single fiber Bragg grating, by subjecting the diffused region to a single exposure using the standard phase-mask technique. A key aspect of our work is the measurement of the out-diffusion through energy dispersive X-ray analysis. Furthermore, we demonstrate the use of the above single-grating filter for discrimination and simultaneous measurement of strain and temperature. The proposed technique provides a significant advantage over other existing methods that require at least two gratings. � 2006 IEEE.