Design and Development of Novel Fiber Bragg Grating based devices for various Biomedical applications

Abstract

Sensors have always been an integral part of human life. Apart from the numerous inherent sensors which the human body possesses, there are various man-made sensors which has been studied and implemented widely to fulfill specific requirements. The design and development of sensors have been carried out utilizing various sensing techniques involving electronical systems, mechanical systems and optical systems. Optical sensors possess advantages such as high speed, high sensitivity and electrical inertness which makes it suitable for many sensing applications including sensing under water, high electromagnetic regions, oil industries etc. Amongst the immense types of optical sensors explored so far, Fiber Bragg Gratings (FBG) has emerged as one of the most desirable optical sensors due to its multi-modal sensing capability, multiplexing capability, large operational bandwidth and high sensitivity. In its elementary form, FBGs are capable of sensing strain and temperature. However, FBGs can be utilized for various other sensing applications such as monitoring pressure, force, residual strain, viscosity, degree of cure, angle, etc. by employing suitable transduction techniques. In present era, FBGs are widely used in diverse sectors such as smart manufacturing industries, civil engineering, aerospace industry, underwater applications etc. which proves the diversity and versatility of the FBG sensors. Further, FBGs have also shown a great potential to be utilized as an effective methodology for bio-medical sensing applications owing to its numerous favoring characteristics such as non-toxicity, small size, chemical and electrical inertness etc. which makes FBG sensors apt for both in vivo and in vitro measurements. In this thesis work, novel Fiber Bragg Grating sensor-based devices have been designed and developed for newer applications in bio-medical sector. Elementarily, novel packaging methodologies for FBGs are devised to monitor the measurand by transducing it to a secondary parameter that can be acquired by the FBG sensor. In the field of Ophthalmology and neuroscience, a novel FBG based eye tracker is devised which can potentially be used to monitor the movements of the eyeball of a person. FBG eye tracker is a minimally invasive device which is worn on the cheeks of the subject with a small probe resting on the lower eyelid of the subject. In this thesis, the FBG eye tracker is utilized to monitor the saccades of the person which is very important to assess the neurological status of the person. Utilizing the data captured by the FBG eye tracker, onset of many serious neurological disorders can be detected at an early level diagnosis. In the field of Orthopedics, FBG based Gait Analysis System (FBG GAS) is developed which essentially consists two novel, wearable, non-invasive devices i.e. Knee Angular Measurement Device (KAMD) and Forefoot load Measurement Device (FLMD). KAMD is capable of dynamic acquisition of knee angular motion and FLMD is a footwear with integrated FBG sensor assembly on its sole which can effectively monitor the load imparted by the forefoot during locomotion. The GAS, collectively, is utilized to study the kinetics and kinematics involved in lower body extremities during various locomotive activities. In the field of Cardiology, a novel, non-invasive pulse pressure acquiring device is designed and developed utilizing FBG which possess the capability to acquire the pulse pressure waveform of the subject on beat-to-beat basis. The device is basically a ring with a diaphragm integrated on it which must be worn by the subject on the finger to acquire the pulse pressure waveform. The developed device acquires the volumetric variations due to blood flowing inside the arteries of the finger through which the pulse pressure waveform is monitored and analyzed. In the field of dentistry, FBG-based temperature sensor is utilized to monitor the temperature rise of the pulp chamber of the human tooth during photopolymerization of various kinds of resins. In this study, two types of light sources are utilized for photopolymerization of resin and the temperature rise due to the light source is observed. Consequentially, the risk involved due to the temperature rise of the pulp chamber during photopolymerization is discussed. To summarize, the present thesis aims to demonstrate a comprehensive experimental study which bring out the utility of FBG sensors in a variety of challenging bio-medical applications which intends to aid doctors, researchers and students working on bio-medical sector.