A NOVEL MULTI-MODAL, WEARABLE SENSING SYSTEM TO AUTOMATICALLY QUANTIFY CHANGES IN EXTRAVASCULAR FLUID LEVELS

The buildup of static edematous fluids (swelling) in the tissue is indicative of a serious medical condition that can lead to long-term tissue damage, reduction in mobility and in some cases loss of limb. This swelling can be due to internal factors such as an immunoresponse to injuries or infections, or external factors such as a leakage of infused intravenous medication to the surrounding tissue (i.e., IV infiltration or extravasation). Detecting and tracking changes in a tissue’s extracellular fluid content is crucial in diagnosing the severity of the injury and/or infection, and thereby preventing irreversible tissue damage. However, current methods for quantifying fluid levels in the extravascular space are either (1) manual and subjective, relying heavily on the medical staff’s expertise, or (2) costly and timely, such as X-rays or magnetic resonance imaging (MRI). In this dissertation, I present non-invasive wearable technologies that utilize localized bioimpedance contextualized by the tissue’s kinematics to robustly quantify changes in the biological tissue’s extracellular fluid content. Towards this goal, several robust and miniaturized systems are designed and implemented by researching different integrated circuits, analog front ends, and novel physiology-driven calibration techniques that together increase the system’s accuracy and reduce its size and power consumption. Next, novel methods and algorithms are developed to allow for unobtrusive real-time detection of changes in extracellular fluid content. The systems, methods and algorithms were validated in human subjects studies, animal models and cadaver models for ankle edema tracking, and in human subjects studies and animal tissue for intravenous infiltration detection.Ph.D

Flexible Electronics for High-Density EMG Based Signal Acquisition for Upper Limb Myoelectric Prosthesis Control

The research detailed in this thesis is aimed at developing flexible electrodes for high-density control of an upper limb myoelectric prosthesis. Different flexible dry electrode materials (made from doped traditionally non-conductive substrates) were used and compared to titanium (which is the industry standard for EMG electrodes). We determined that conductivity measurements alone, (the current industry standard for characterizing electrical properties of materials), are not sufficient due to their complex impedance. We measured the skin electrode complex impedance and relationship with signal to noise ratio (SNR) and settling time. We show that complex skin electrode impedance is linearly related to the SNR of signals and that complex skin electrode impedance better characterizes the electrical properties of doped, traditionally non-conductive materials for physiological signal acquisition. Next we constructed a flexible high-density array with 128- contact points arranged in an 8 x 16 configuration to cover the entire residual limb. Myoelectric signals, and its relationship to derived time domain features of all 128 channels were extracted and represented as spatio-temporal values as 8 x 16 images to represent the muscle activity map of the residual limb. Thus, a traditional signal-processing problem is converted into an image processing problem. Obtaining High Density (HD) (128 channel) spatio-temporal information has significant merits which include: ability to easily identify the optimum myoelectric recording sites on a residual limb, ability to temporally study the onset and decline of a contraction, predicting the stage of contraction and, finally, ability to implement proportional control and fine motor myoelectric control

A novel approach to the 'pressing problem' of lymphoedema - engineering a foundation for clinical standards and efficacy-based compression therapy

Lymphoedema, particularly as manifested in a secondary form following previous intervention or trauma, is a progressive and debilitating disorder, embodied through the gradual volumetric swelling of a patient’s limb(s), often leading to fibrosis as well as loss of limb function in extreme cases. Compression-based therapy, the most prevalent prophylaxis and post-onset treatment approach for lymphoedema, has shown only limited success. A clear lack of standards, i.e., guidelines insuring consistency of structure and function of lymphoedema compression sleeves, hinders progress toward finding a cure for lymphoedema and prevents testing of sleeve efficacy. The body of work included in this thesis highlights the specific areas of focus necessary to move the field forward and sets a path towards comprehensive profiling of compression sleeves, to understand the underlying mechanisms relevant to efficacious treatment at the interface of the sleeve and skin. Current high-resolution commercial pressure sensors proved ineffective for measurement of spatial and temporal pressure profiles of sleeves in situ; limitations of such compliant sensors, and specific areas of needed improvement, were identified. Promising prototypes of flexible, high-resolution custom sensors were also assessed, with preliminary data and their shortfalls leading to definition of technical specifications for the future. Finally, a Digital Image Correlation (DIC)-based approach was applied to map strains of compression sleeves in high resolution and in situ. The DIC-method platform was tested and validated as a means to provide qualitative and quantitative characterisation of compression sleeves as a function of sleeve size, class, and manufacturer independent of lymphoedema state. Unexpected differences in pressure profiles underscore the need for both standardisation of sleeve design as well as follow on studies testing sleeve function in lymphoedema patients. Looking toward the future, testing of efficacy and head-to-head comparison of standardised and bespoke garments will better enable mechanistic understanding of lymphoedema's aetiology, unraveling how the ‘global’ disease state emerges from ‘local’ events, leading to a basis for lymphoedema prevention in the future

Actas de SABI2020

Los temas salientes incluyen un marcapasos pulmonar que promete complementar y eventualmente sustituir la conocida ventilación mecánica por presión positiva (intubación), el análisis de la marchaespontánea sin costosos equipamientos, las imágenes infrarrojas y la predicción de la salud cardiovascular en temprana edad por medio de la biomecánica arterial

Thermo-Mechanical Modeling and the Application of Coiled Polymer Actuators in Soft Robotics and Biomimetics

Coiled polymer actuators (CPA) are a recently discovered smart material. Due to their large tensile stoke and power densities they are often used as actuators or artificial muscles. CPA’s are fabricated from a polymer fiber, typically nylon, mechanically twisted into a coil or coiled around a mandrel and annealed. When heated over the glass transition temperature they can contract, expand or exhibit torsional actuation, depending on the fabrication method and end conditions. The fabrication and application of CPA is well documented and has made many innovations in the fields of smart materials, soft robotics and the likes. However, there is a lack of knowledge in the modeling of CPA, this is partly due to the novelty of the actuator. To address this problem, a theoretical and experimental investigation of thermo-mechanical response is proposed. An energy and variational methods and continuum mechanics approach is utilized with numerical methods to describe the actuation response. To verify the model, the numerical simulation displacement response is compared to CPA samples that are fabricated and experimentally tested in lab using a dynamic machine analyzer (DMA). The results indicate the proposed model accurately predict the actuation response of the CPA under thermal loading. The numerical simulation and experimental comparison is in good agreement and helps to further understand the underlining cause of the actuation behavior of the coiled polymer actuator. Furthermore, the model can be used in application purposes where the results of the model can be used in designing and optimizing soft robotics using CPA as an artificial muscle. In addition to the numerical and experimental investigation of the CPA’s thermomechanical response, an application in biomimetics is being studied. Biomimetics is an interdisciplinary field in engineering and sciences used to overcoming complex human challenges by designing and fabricating materials and systems modeled after nature. Applications of biomimicry can be seen in many technological advancements such as catheters, hearing devices, and artificial appendages such as arms, legs and fingers. The inspiration for this study is the hydrofoil like structured pectoral fin of the Harbor Porpoise whale. Studies will be focused on understanding the fluid forces acting on the pectoral fin. First and foremost, a highly accurate pectoral fin is fabricated from CT scans of a Harbor Porpoise whale fin. 3D models are obtained using Simpleware ScanIP and post-processed in Autodesk for 3D printing components, which were used to assemble to artificial whale fin. An array of thermally driven Coiled Polymer Actuators (CPA) fabricated from Nylon and heated with Nichrome are used as artificial muscles for actuating the pectoral fin. CPA’s were used for their similarity to biological muscles and are of great interest due to its high specific power and large actuation stroke. A simple control circuit for supplying power to the Nichrome heating wires is developed using an Arduino and motor drivers. The displacement over time of the fin is tested and captured using a laser distant sensor. The fin shows a great displacement response, largely deflecting in both direction relative to its size. The artificial fin was then be further utilized in our studies. The fluid forces imposed on the fin while in motion was measured in a laboratorycontrolled setting. A low-velocity belt driven tow tank was used to displace the artificial fin through water. The tow velocity was varied, and the drag force measurements were taken with and without fin actuation using a cantilever beam load cell. A theoretical derived drag force was compared to the experimental drag data and showed good comparison for the non-actuated fin. Increased drag was exhibited with actuation in both directions when towed through water. This demonstrates the ability of the fin to manipulate is geometry to change the drag force on itself serving as a controllable hydrofoil. We hope to elaborate on this ability and apply it to mechanical designs such as under and above water vehicles

XXII International Conference on Mechanics in Medicine and Biology - Abstracts Book

This book contain the abstracts presented the XXII ICMMB, held in Bologna in September 2022. The abstracts are divided following the sessions scheduled during the conference

New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging

Jöbsis was the first to describe the in vivo application of near-infrared spectroscopy (NIRS), also called diffuse optical spectroscopy (DOS). NIRS was originally designed for the clinical monitoring of tissue oxygenation, and today it has also become a useful tool for neuroimaging studies (functional near-infrared spectroscopy, fNIRS). However, difficulties in the selective and quantitative measurements of tissue hemoglobin (Hb), which have been central in the NIRS field for over 40 years, remain to be solved. To overcome these problems, time-domain (TD) and frequency-domain (FD) measurements have been tried. Presently, a wide range of NIRS instruments are available, including commonly available commercial instruments for continuous wave (CW) measurements, based on the modified Beer–Lambert law (steady-state domain measurements). Among these measurements, the TD measurement is the most promising approach, although compared with CW and FD measurements, TD measurements are less common, due to the need for large and expensive instruments with poor temporal resolution and limited dynamic range. However, thanks to technological developments, TD measurements are increasingly being used in research, and also in various clinical settings. This Special Issue highlights issues at the cutting edge of TD DOS and diffuse optical tomography (DOT). It covers all aspects related to TD measurements, including advances in hardware, methodology, the theory of light propagation, and clinical applications