Cátia Leitão

Feasibility studies of Bragg probe for noninvasive carotid pulse waveform assessment.

Abstract. The arterial stiffness evaluation is largely reported as an independent predictor of cardiovascular diseases. The central pulse waveform can provide important data about arterial health and has been studied in patients with several pathologies, such as diabetes mellitus, coronary artery disease and hypertension. The implementation and feasibility studies of a fiber Bragg grating probe for noninvasive monitoring of the carotid pulse are described based on fiber Bragg grating technology. Assessment tests were carried out in carotids of different volunteers and it was possible to detect the carotid pulse waveform in all subjects. In one of the subjects, the sensor was also tested in terms of repeatability. Although further tests will be required for clinical investigation, the first studies suggest that the developed sensor can be a valid alternative to electromechanical tonometers.

Plastic Optical Fiber Sensor for Noninvasive Arterial Pulse Waveform Monitoring

Central arterial pulse pressure monitoring has been considered a key factor in hypertension assessment and cardiovascular prevention. In this paper, it is presented an intensity-based plastic optical fiber sensor for noninvasive monitoring of the carotid pulse waveform. The advantages of this sensing method are the low implementation cost, high robustness, and the signal processing simplicity. The sensor showed a suitable sensitivity to movements up to 370 μm, with a displacement resolution of 0.1 μm. As preliminary proof of concept, the sensor was used to detect the arterial pulse waveform in some human subjects, allowing the assessment of key indexes for heart and arterial stiffness evaluation, such as augmentation index, subendocardial viability ratio, and ejection duration.

Insole optical fiber Bragg grating sensors network for dynamic vertical force monitoring

Abstract. In an era of unprecedented progress in technology and increase in population age, continuous and close monitoring of elder citizens and patients is becoming more of a necessity than a luxury. Contributing toward this field and enhancing the life quality of elder citizens and patients with disabilities, this work presents the design and implementation of a noninvasive platform and insole fiber Bragg grating sensors network to monitor the vertical ground reaction forces distribution induced in the foot plantar surface during gait and body center of mass displacements. The acquired measurements are a reliable indication of the accuracy and consistency of the proposed solution in monitoring and mapping the vertical forces active on the foot plantar sole, with a sensitivity up to 11.06  pm/N. The acquired measurements can be used to infer the foot structure and health condition, in addition to anomalies related to spine function and other pathologies (e.g., related to diabetes); also its application in rehabilitation robotics field can dramatically reduce the computational burden of exoskeletons’ control strategy. The proposed technology has the advantages of optical fiber sensing (robustness, noninvasiveness, accuracy, and electromagnetic insensitivity) to surpass all drawbacks verified in traditionally used sensing systems (fragility, instability, and inconsistent feedback).

Internal and External Temperature Monitoring of a Li-Ion Battery with Fiber Bragg Grating Sensors

The integration of fiber Bragg grating (FBG) sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to 8C. The FBG sensors were placed both outside and inside the cell, located in the center of the electrochemically active area and at the tab-electrode connection. The internal sensors recorded temperature variations of 4.0 ± 0.1 °C at 5C and 4.7 ± 0.1 °C at 8C at the center of the active area, and 3.9 ± 0.1 °C at 5C and 4.0 ± 0.1 °C at 8C at the tab-electrode connection, respectively. This study is intended to contribute to detection of a temperature gradient in real time inside a cell, which can determine possible damage in the battery performance when it operates under normal and abnormal operating conditions, as well as to demonstrate the technical feasibility of the integration of in-operando microsensors inside Li-ion cells.

POFBG-Embedded Cork Insole for Plantar Pressure Monitoring

We propose a novel polymer optical fiber (POF) sensing system based on fiber Bragg gratings (FBGs) to measure foot plantar pressure. The plantar pressure signals are detected by five FBGs, in the same piece of cyclic transparent optical polymer (CYTOP) fiber, which are embedded in a cork insole for the dynamic monitoring of gait. The calibration and measurements performed with the suggested system are presented, and the results obtained demonstrate the accuracy and reliability of the sensing platform to monitor the foot plantar pressure distribution during gait motion and the application of pressure. This architecture does not compromise the patient’s mobility nor interfere in their daily activities. The results using the CYTOP fiber showed a very good response when compared with solutions using silica optical fibers, resulting in a sensitivity almost twice as high, with excellent repeatability and ease of handling. The advantages of POF (e.g., high flexibility and robustness) proved that this is a viable solution for this type of application, since POF’s high fracture toughness enables its application in monitoring patients with higher body mass compared with similar systems based on silica fiber. This study has demonstrated the viability of the proposed system based on POF technology as a useful alternative for plantar pressure detection systems.

Central arterial pulse waveform acquisition with a portable pen-like optical fiber sensor.

ObjectivePulse waveform features related to cardiovascular pathologies and arterial stiffness have been extensively studied, and optical fiber sensors have been studied with an aim to simplify the pulse waveform acquisition in the carotid artery. In this paper, a novel optical fiber sensor to record pulse waveform in the carotid artery has been proposed. MethodsThe pulse waveform optical fiber sensor design, based on fiber Bragg gratings, is presented. The probe was characterized, and its response to controlled waveforms was studied. Finally, tests were performed on human subjects. ResultsThe developed sensor has a displacement sensitivity of 21.2 pm/&mgr;m, with ability to detect the carotid pulse wave in the neck surface, with a resolution of 1.3 mmHg. ConclusionThis study revealed a new technological approach for acquisition of the central pulse waveform.

Lithium batteries temperature and strain fiber monitoring

Fiber Bragg grating sensors were attached to the surface of a rechargeable lithium battery in order to monitor its thermal and strain fluctuations through charge and different discharge C rates. During the discharge process above 1C, it were observed, a temperature and strain fluctuations of a 4.12 ± 0.67 °C and 24.64 ± 6.02 με, respectively. In the regular charge process, a temperature and strain variation of 1.03 ± 0.67 °C and 15.86 ± 6.02 με, were detected.

Low-Cost Interrogation Technique for Dynamic Measurements with FBG-Based Devices

Fiber Bragg gratings are widely used optical fiber sensors for measuring temperature and/or mechanical strain. Nevertheless, the high cost of the interrogation systems is the most important drawback for their large commercial application. In this work, an in-line Fabry–Perot interferometer based edge filter is explored in the interrogation of fiber Bragg grating dynamic measurements up to 5 kHz. Two devices an accelerometer and an arterial pulse wave probe were interrogated with the developed approach and the results were compared with a commercial interrogation monitor. The data obtained with the edge filter are in agreement with the commercial device, with a maximum RMSE of 0.05 being able to meet the requirements of the measurements. Resolutions of 3.6 pm and 2.4 pm were obtained, using the optical accelerometer and the arterial pulse wave probe, respectively.

Development of a FBG probe for non-invasive carotid pulse waveform assessment

One of the early predictors of cardiovascular diseases, with growing interest, is the arterial stiffness which is typically evaluated through the velocity and morphology of the arterial pressure wave. In each cardiac cycle the heart generates a pressure wave which propagates through the arterial tree. Along its path, the pressure wave interacts with the arterial walls and, consequently, the morphology of a local arterial pressure wave can be assessed by the arterial distention movement. Due to its superficiality, proximity of the heart and high probability of atherosclerosis development, the carotid artery has particular interest to be monitored. In this work, the development of a non-invasive fibre Bragg grating (FBG) probe for the acquisition of the arterial distention wave is presented. Comparing to traditional methods, optical FBG based sensors can offer many advantages, namely, compactness, immunity to electromagnetic interference, high sensitivity, low noise and immunity to light source intensity due to its codification in the wavelength domain. The arterial movements induce strain on a uniform FBG, with the arterial distention pattern. The carotid pulse wave was successful accessed in young human carotid artery, with an acquisition rate of 950 Hz, allowing a clear distinction of the carotid pulse identification points.

Insole optical fiber sensor architecturefor remote gait analysis - an eHealth Solution

The advances and fast spread of mobile devices and technologies, we witness today, have extended its advantages over medical and health practice supported by mobile devices, giving rise to the growing research of Internet of Things (IoT), especially the e-Health field. The features provided by mobile technologies revealed to be of major importance when we consider the continuous aging of population and the consequent increase of its debilities. In addition to the increase of lifetime span of population, also the increase of health risks and their locomotive impairments increases, requiring a close monitoring and continuous evaluation. Such monitoring should be as noninvasive as possible, in order not to compromise the mobility and the day-to-day activities of citizens. Therefore, we present the development of a noninvasive optical fiber sensor (OFS) architecture adaptable to a shoe sole for plantar pressure remote monitoring, which is suitable to be integrated in an IoT e-Health solution to monitor the wellbeing of individuals. This paper explores the production of the OFS multiplexed network (using fiber Bragg gratings) to monitor the foot plantar pressure distribution during gait (walking movement). From the acquired gait data, it is possible to infer health conditions of the patient’s foot and spine posture. To guarantee the patients mobility, the proposed system consists of an OFS network integrated with a wireless transceiver to enable efficient ubiquitous monitoring of patients. This paper shows the calibration and measurement results, which reflect the accuracy of the proposed system, under normal walking in controlled area.