Design and simulation of a multi-function MEMS sensor for health and usage monitoring.

Health and usage monitoring as a technique for online test, diagnosis or prognosis of structures and systems has evolved as a key technology for future critical systems. The technology, often referred to as HUMS is usually based around sensors that must be more reliable than the system or structure they are monitoring. This paper proposes a fault tolerant sensor architecture and demonstrates the feasibility of realising this architecture through the design of a dual mode humidity/pressure MEMS sensor with an integrated temperature function. The sensor has a simple structure, good linearity and sensitivity, and the potential for implementation of built-in-self-test features. We also propose a re-configurable sensor network based on the multi-functional sensor concept that supports both normal operational and fail safe modes. The architecture has the potential to significantly increase system reliability and supports a reduction in the number of sensors required in future HUMS devices. The technique has potential in a wide range of applications, especially within wireless sensor networks

Design, development and characterisation of piezoresistive and capacitive polymeric pressure sensors for use in compression hosiery

The work in this thesis was focused in developing a flexible and cost-effective pressure sensor capable of detecting pressure variations within the low working range (0-6kPa) of compression hosiery. For this cause, both piezoresistive and capacitive pressure sensors were developed and characterised, utilising conductive and non-conductive polymeric elements to sense compressive loads. In the first case, the developed piezoresistive sensor is composed of a conductive filler - polymer composite, with a force-dependent conductivity, encapsulated in between a structured and unstructured configuration of electrodes. Initially, as the sensing element of the sensor a multi-walled carbon nanotubes-polydimethylsiloxane (MWCNT-PDMS) composite was tested. A fabrication process is also proposed for developing the MWCNT-PDMS composite which involves a series of successive direct ultrasonications and shear mixing in order to disperse the two constituents of the composite, with the use of an organic solvent. Developing the composite over a range of different filler concentrations revealed a sharp step-like conductivity behaviour, typical amongst percolating composites. The MWCNT-PDMS sensor exhibited a positive piezoresistive response when subjected to compression, which was substantially enhanced when structured electrode layers were utilised. A Quantum Tunnelling Composite (QTC) material was also tested as the sensing material, which displays a large negative piezoresistive response when deformed. The QTC pressure sensor exhibited an improved performance, which was similarly significantly increased when a structured electrode was employed. In the second case, a parallel-plate capacitive pressure sensor was developed and characterised, which successfully provided a pressure sensitivity within the working range of compression hosiery. The sensor employs an ultra-thin PDMS blend film, with tuneable Young’s modulus, as the dielectric medium of the capacitor, bonded in between two rigid copper-coated glass layers. A casting process is also presented, involving the use of a sacrificial mould, in order to pattern the polymeric film with a micro-pillar structure to assist the deformation of the medium under compressive loads. The performance of the sensor with regards to the polymeric film thickness, structure and mechanical softness was explored. Overall, the combination of an ultra-thin dielectric medium with a very low Young’s modulus and a microstructured surface resulted in a capacitive pressure sensor with a good performance within the desired pressure regime

Generalized Parity-Time Symmetry Condition for Enhanced Sensor Telemetry

Wireless sensors based on micro-machined tunable resonators are important in a variety of applications, ranging from medical diagnosis to industrial and environmental monitoring.The sensitivity of these devices is, however, often limited by their low quality (Q) factor.Here, we introduce the concept of isospectral party time reciprocal scaling (PTX) symmetry and show that it can be used to build a new family of radiofrequency wireless microsensors exhibiting ultrasensitive responses and ultrahigh resolution, which are well beyond the limitations of conventional passive sensors. We show theoretically, and demonstrate experimentally using microelectromechanical based wireless pressure sensors, that PTXsymmetric electronic systems share the same eigenfrequencies as their parity time (PT)-symmetric counterparts, but crucially have different circuit profiles and eigenmodes. This simplifies the electronic circuit design and enables further enhancements to the extrinsic Q factor of the sensors

Smart Devices and Systems for Wearable Applications

Wearable technologies need a smooth and unobtrusive integration of electronics and smart materials into textiles. The integration of sensors, actuators and computing technologies able to sense, react and adapt to external stimuli, is the expression of a new generation of wearable devices. The vision of wearable computing describes a system made by embedded, low power and wireless electronics coupled with smart and reliable sensors - as an integrated part of textile structure or directly in contact with the human body. Therefore, such system must maintain its sensing capabilities under the demand of normal clothing or textile substrate, which can impose severe mechanical deformation to the underlying garment/substrate. The objective of this thesis is to introduce a novel technological contribution for the next generation of wearable devices adopting a multidisciplinary approach in which knowledge of circuit design with Ultra-Wide Band and Bluetooth Low Energy technology, realization of smart piezoresistive / piezocapacitive and electro-active material, electro-mechanical characterization, design of read-out circuits and system integration find a fundamental and necessary synergy. The context and the results presented in this thesis follow an “applications driven” method in terms of wearable technology. A proof of concept has been designed and developed for each addressed issue. The solutions proposed are aimed to demonstrate the integration of a touch/pressure sensor into a fabric for space debris detection (CApture DEorbiting Target project), the effectiveness of the Ultra-Wide Band technology as an ultra-low power data transmission option compared with well known Bluetooth (IR-UWB data transmission project) and to solve issues concerning human proximity estimation (IR-UWB Face-to-Face Interaction and Proximity Sensor), wearable actuator for medical applications (EAPtics project) and aerospace physiology countermeasure (Gravity Loading Countermeasure Skinsuit project)

Interfacing biomimetics and nanomaterials for next generation wearables

With the steady rise in average life expectancy across the globe in the last century, lifestyle related diseases are causing a burden on existing healthcare infrastructure. Emerging complex diseases cause significant impact on productive man hours and burden the existing healthcare system. For instance, people suffering from progressive neurodegenerative disorders like Parkinson’s disease, multiple sclerosis, and Huntington’s disease must be monitored frequently to track the progress of the diseases. Due to the life altering nature of these neurodegenerative diseases, it becomes very difficult for the patients to return to their daily routine, considering the fact that a significant amount of their time is spent in hospital-based diagnostic and rehabilitation centres. Other less serious complications, like sleep apnoea, post-trauma recovery, and similar conditions also need regular progress tracking and medical intervention (if necessary) and can cause disruptions to daily life due to frequent hospital stays. Inexpensive, accurate, and power efficient wearable sensors will be playing a major role in facilitating the health 3.0 in the foreseeable future. Particularly, the onslaught of COVID-19 pandemic since late 2019 have fuelled the demand for wearable sensors capable of human physiological vitals monitoring.The need of the hour is efficient, non-invasive, wearable sensors capable of gathering vital human physiological parameters round the clock and store the data in cloud for remote access by healthcare specialists. However, for any sensor to be considered seriously in healthcare space, parameters like sensitivity, ease of use, cost effectiveness, long term reliability and most importantly, low power budget are of paramount importance. Other than applications in human physiological monitoring, flexible sensors are relevant for applications involving artificial skins for next generation prosthesis, soft human-machine interface, and robotics assisted medical facilities.Nature is full of unique designs to tackle interesting problems we encounter daily. For instance, the seamless entry of a Kingfisher from a low resistance medium (air) to a high resistance medium (water) is nothing short of an extraordinary aerodynamic design marvel. Interfacing nanotechnology with biomimetics is important in the context of next generation wearables as it can lead to the development of a class of highly reliable and inexpensive wearable sensors tailored to cater the urgent needs of physiological parameter monitoring.This thesis has been a humble effort towards creating a seamless integration between the concepts of bioinspiration and Microsystems-enabled miniaturized sensors for tackling a wide variety of problems we encounter in our daily life. Two most widely used and traditional mechanisms of sensing entailing piezoresistive and capacitive sensing were investigated and a bioinspiration approach was taken to device next generation flexible and wearable devices. A wide variety of practical problems ranging from human gait monitoring to low powered flow sensing has been tackled taking inspiration from nature

Microfluidic Sensors and Circuits for Internet of Things Applications

As we move into the Internet of Things (IoT) and cloud computing era, the number of sensors deployed which seamlessly integrate themselves into environment is growing rapidly. These sensors should be minimally intrusive, both optically and mechanically, while providing high temporal and spatial contextual awareness of its environment. In this chapter, microfluidic sensors and circuits are presented to better bridge the physical and digital world for healthcare applications. Specifically, a discussion of cardiovascular sensing, glaucoma diagnosis and flexible tactile sensor arrays for smart skin application is presented

A smart tool for the diagnosis of Parkinsonian syndrome using wireless watches

This work is licensed under a Creative Commons Attribution 3.0 License.Early detection and diagnosis of Parkinson disease will provide a good chance for patients to take early actions and prevent its further development. In this paper, a smart tool for the diagnosis of Parkinsonian syndromes is designed and developed using low-cost Texas Instruments eZ430-Chronos wireless watches. With this smart tool, Parkinson Bradykinesia is detected based on the cycle of a human gait, with the watch worn on the foot, and Parkinson Tremor shaking is detected and differed by frequency 0 to 8 Hz on the arm in real-time with a developed statistical diagnosis chart. It can be used in small clinics as well as home environment due to its low-cost and easy-use property

Advances in Wearable Sensing Technologies and Their Impact for Personalized and Preventive Medicine

Recent advances in miniaturized electronics, as well as mobile access to computational power, are fostering a rapid growth of wearable technologies. In particular, the application of such wearable technologies to health care enables to access more information from the patient than standard episodically testing conducted in health provider centres. Clinical, behavioural and self-monitored data collected by wearable devices provide a means for improving the early-stage detection and management of diseases as well as reducing the overall costs over more invasive standard diagnostics approaches. In this chapter, we will discuss some of the ongoing key innovations in materials science and micro/nano-fabrication technologies that are setting the basis for future personalized and preventive medicine devices and approaches. The design of wire- and power-less ultra-thin sensors fabricated on wearable biocompatible materials that can be placed in direct contact with the body tissues such as the skin will be reviewed, focusing on emerging solutions and bottlenecks. The application of nanotechnology for the fabrication of sophisticated miniaturized sensors will be presented. Exemplary sensor designs for the non-invasive measurement of ultra-low concentrations of important biomarkers will be discussed as case studies for the application of these emerging technologies

The LISA pathfinder mission

ISA Pathfinder (LPF), the second of the European Space Agency's Small Missions for Advanced Research in Technology (SMART), is a dedicated technology validation mission for future spaceborne gravitational wave detectors, such as the proposed eLISA mission. LISA Pathfinder, and its scientific payload - the LISA Technology Package - will test, in flight, the critical technologies required for low frequency gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. This is achieved through technology comprising inertial sensors, high precision laser metrology, drag-free control and an ultra-precise micro-Newton propulsion system. LISA Pathfinder is due to be launched in mid-2015, with first results on the performance of the system being available 6 months thereafter. The paper introduces the LISA Pathfinder mission, followed by an explanation of the physical principles of measurement concept and associated hardware. We then provide a detailed discussion of the LISA Technology Package, including both the inertial sensor and interferometric readout. As we approach the launch of the LISA Pathfinder, the focus of the development is shifting towards the science operations and data analysis - this is described in the final section of the paper