Supercapacitive Sensors for Force/Strain Measurements in Biomedical Applications

University of Minnesota Ph.D. dissertation. August 2019. Major: Mechanical Engineering. Advisor: Rajesh Rajamani. 1 computer file (PDF); xvi, 117 pages.This dissertation develops a new class of flexible force and strain sensors based on the principle of supercapacitive sensing. The sensing mechanism consists of a change in capacitance in a double-layer supercapacitor in response to an applied force or strain by inducing a change in the contact area between an electrolyte and a pair of electrodes. The new sensors can provide a measurement sensitivity several orders of magnitude higher than traditional capacitive sensors, and have other advantages such as flexibility, soft material construction, ability to operate in liquid environments, tremendous ease of fabrication and unprecedented configurability. As a key component of the new sensors, a paper-based solid-state electrolyte with high deformability is developed. The paper substrate can be easily cut and shaped into complex three-dimensional geometries on which ionic gel can be coated. Paper dissolves in the ionic gel after determining the shape of the electrolyte, leaving behind transparent electrolyte structures with micro-structured fissures responsible for their high deformability. Exploiting this simple paper-based fabrication process, this dissertation develops diverse sensors of different configurations and demonstrates their operation and their advantages. First, force sensors in multiple configurations involving electrolytes that are arch-shaped, corrugated and dome-shaped are fabricated. They have sensitivity that is 1000 times larger than similarly sized capacitive sensors and have negligible parasitic capacitance when used in immersive liquid environments. The use of such force sensors on a urethral catheter which can be used to diagnose the cause of urinary incontinence in a Urology application is demonstrated. A urethral catheter with five distributed force sensors is fabricated that can be used to measure distributed urethral closure pressure in a human subject. Experimental results with the catheter, including cuff tests and ex vivo tests are presented. Next, their high sensitivity allows the use of multiple supercapacitive sensors together in a quad structure to enable a sensor in which normal and shear forces can be simultaneously measured. Such a sensor can have multiple applications in robotics and in wearable monitoring systems which can benefit from measurement of multi-axis forces. The performance of the multi-axis normal-shear force sensor is evaluated using extensive experimental data with a wide range of force combinations. Due to manufacturing imperfections, the sensor does not have uniform axisymmetric sensitivity. Hence, a learning algorithm which utilizes a deep neural network to model the sensor response to multi-axis forces is developed and implemented. The learning algorithm allows the sensor system to provide highly accurate normal and shear force estimates, no matter what the alignment of the forces applied on the sensor. Finally, the use of the supercapacitive sensors for strain measurement is evaluated. The paper-based electrolyte is strengthened with silicate nanoparticles to allow it to withstand over 110% stretch without failure. The strengthened electrolyte is used in a unique strain sensor design. The strain sensor is shown to have ultra-high sensitivity and its performance in a wearable home-monitoring application to measure the size of the leg and thus monitor leg-swelling is demonstrated. The contributions of this dissertation include the development of a new soft deformable electrolyte, the development of a paper-based supercapacitive sensor system, and the development of novel sensor configurations such as a simultaneous normal-shear force sensor, a distributed urethral catheter with multiple pressure sensors and a highly stretchable strain sensor. The developed class of new sensors provides extremely high sensitivity and other advantages in spite of easy fabrication with no requirement for clean room facilities

Method and apparatus for monitoring an organ of a patient

An implanted device for an organ of a patient including a housing. The device includes a detector having electrodes that have a varying distance over time between them which produces a detector signal based on electrical signals derived from the organ. The device includes a signal processor disposed in the housing in communication with the detector which determines admittance from the detector signal based on the varying distance over time between the electrodes. The device includes a drive circuit disposed in the housing to cause the electrodes to generate emitted electrical signals. A method for monitoring a patient's organ.Board of Regents, University of Texas Syste

Heating technology for malignant tumors: a review

The therapeutic application of heat is very effective in cancer treatment. Both hyperthermia, i.e., heating to 39-45 degrees C to induce sensitization to radiotherapy and chemotherapy, and thermal ablation, where temperatures beyond 50 degrees C destroy tumor cells directly are frequently applied in the clinic. Achievement of an effective treatment requires high quality heating equipment, precise thermal dosimetry, and adequate quality assurance. Several types of devices, antennas and heating or power delivery systems have been proposed and developed in recent decades. These vary considerably in technique, heating depth, ability to focus, and in the size of the heating focus. Clinically used heating techniques involve electromagnetic and ultrasonic heating, hyperthermic perfusion and conductive heating. Depending on clinical objectives and available technology, thermal therapies can be subdivided into three broad categories: local, locoregional, or whole body heating. Clinically used local heating techniques include interstitial hyperthermia and ablation, high intensity focused ultrasound (HIFU), scanned focused ultrasound (SFUS), electroporation, nanoparticle heating, intraluminal heating and superficial heating. Locoregional heating techniques include phased array systems, capacitive systems and isolated perfusion. Whole body techniques focus on prevention of heat loss supplemented with energy deposition in the body, e.g., by infrared radiation. This review presents an overview of clinical hyperthermia and ablation devices used for local, locoregional, and whole body therapy. Proven and experimental clinical applications of thermal ablation and hyperthermia are listed. Methods for temperature measurement and the role of treatment planning to control treatments are discussed briefly, as well as future perspectives for heating technology for the treatment of tumors

Applications and Experiences of Quality Control

The rich palette of topics set out in this book provides a sufficiently broad overview of the developments in the field of quality control. By providing detailed information on various aspects of quality control, this book can serve as a basis for starting interdisciplinary cooperation, which has increasingly become an integral part of scientific and applied research

Technology 2000, volume 1

The purpose of the conference was to increase awareness of existing NASA developed technologies that are available for immediate use in the development of new products and processes, and to lay the groundwork for the effective utilization of emerging technologies. There were sessions on the following: Computer technology and software engineering; Human factors engineering and life sciences; Information and data management; Material sciences; Manufacturing and fabrication technology; Power, energy, and control systems; Robotics; Sensors and measurement technology; Artificial intelligence; Environmental technology; Optics and communications; and Superconductivity

Removal of cardiovascular obstructions by spark erosion

Coronary atherosclerosis, leading to coronary artery stenosis, is the main cause for ischemic health disease in the Westem countries. Stenoses manifest themselves by limiting blood supply to the myocardium thus causing complaints. A long history of degenerative atherosclerotic disease of the intimal wall of the coronary vessels has usually preceded these events. Probably because of this long term process the composition of the accumulated obstructive tissue is quite heterogeneous and consists of a variety of cells and extra cellular material like lipid containing macrophages, smooth muscle cells, Illonocytes, collagen. cholesterol crystals and calcium. In addition, fresh or organized thrombi may have been deposited on these plaques. Regression of these lesions may be obtained by lifestyle changes or lipid lowering therapy. The acute invasive removal of such complex lesions, however, cannot be achieved by applying simple mechanical or chemical means

Medical Robotics

The first generation of surgical robots are already being installed in a number of operating rooms around the world. Robotics is being introduced to medicine because it allows for unprecedented control and precision of surgical instruments in minimally invasive procedures. So far, robots have been used to position an endoscope, perform gallbladder surgery and correct gastroesophogeal reflux and heartburn. The ultimate goal of the robotic surgery field is to design a robot that can be used to perform closed-chest, beating-heart surgery. The use of robotics in surgery will expand over the next decades without any doubt. Minimally Invasive Surgery (MIS) is a revolutionary approach in surgery. In MIS, the operation is performed with instruments and viewing equipment inserted into the body through small incisions created by the surgeon, in contrast to open surgery with large incisions. This minimizes surgical trauma and damage to healthy tissue, resulting in shorter patient recovery time. The aim of this book is to provide an overview of the state-of-art, to present new ideas, original results and practical experiences in this expanding area. Nevertheless, many chapters in the book concern advanced research on this growing area. The book provides critical analysis of clinical trials, assessment of the benefits and risks of the application of these technologies. This book is certainly a small sample of the research activity on Medical Robotics going on around the globe as you read it, but it surely covers a good deal of what has been done in the field recently, and as such it works as a valuable source for researchers interested in the involved subjects, whether they are currently “medical roboticists” or not

Advanced fibre gratings in near- and mid-infrared region and their applications for structure monitoring and biosensing

This thesis emphasises an elaborate research finding on the fabrication, analysis of resonance spectral response and sensing applications in various fields using different type of optical fibre grating devices over an entire wavelength range from near- to mid-infrared (IR). Firstly, the major contribution described in the thesis is a thorough investigation of sensor structures, detailed in respect to writing techniques for optical fibre gratings irradiated by a frequency-doubled Argon ion laser. Thereafter spectral modulation for these UV-inscribed fibre Bragg gratings (FBGs), long period gratings (LPGs) and tilted fibre gratings (TFGs) of small and large angled structures are analysed. Special LPG devices with both dual peaks and 1st&2nd orders, and excessively tilted TFGs (Ex-TFGs) are also achieved with the resonances in the mid-IR range for enhanced sensitivity. Investigations of different sensing measurements, such as temperature, strain, bending and surrounding refractive index (SRI) for these fibre grating devices are performed. Another important contribution is the study on experimental investigation for the fabrication of FBGs into multicore fibre such as four core fibre (4CF) with two different core spacings and seven core fibre (7CF) are explained. A selective inscription method is utilised for inscribing FBGs into different cores of multicore fibre (MCF). The measurement performance with vector bend/twist sensing results in an enhanced sensitivity for FBGs in the distributed cores around the circumference of 4CF and 7CF is analysed in detail, showing the effective detection of both amplitude and direction. Whereas, in 7CF the central core FBG acts as the temperature reference having low bending sensitivity of -8.83 pm/m-1, presenting extra function for eliminating temperature cross-talk effect. The application for these grating devices is largely associated to structural monitoring in astronomy, biomedical sciences, and robotics. Finally, I have investigated different enzyme functionalised and nano-deposited LPG devices for bio and environmental sensing applications. The experimental findings for these sensors are discussed in glucose sensing measurements by observing resonance wavelength shift. Whereas LPGs fabricated with mono or multi-layered deposition of 2D nanomaterials, such as graphene oxide (GO) solution and single walled carbon nanotubes (SWCNT) are demonstrated with SRI measurement. Here, the fabricated devices show a significant intensity change into the transmission spectrum. The resonance response is observed in the near- to mid-IR ranges. This enhanced sensitivity is utilised for haemoglobin sensing in the detection of anaemia in human body and relative humidity sensing for monitoring environmental condition respectively. All demonstrated optical fibre grating based sensors have potential for a wide range of future applications in industry, medical and environmental sectors