Research on Signal Pickup System for the Wireless Passive LC Resonant Pressure Sensor

在高温、潮湿等恶劣的环境中以及眼内压测量、疤痕治疗等应用场合，不便利用有线有源的传感器进行压力监测，LC谐振式无线压力传感器采用无线无源方式实现对压力信号的提取，拓展了压力传感器的应用范围。目前，LC谐振式无线压力传感器的信号拾取主要使用网络分析仪或阻抗分析仪，不仅成本高，而且携带不便，极大限制了非实验室场合的应用。本文针对LC谐振式无线MEMS压力传感器的信号拾取现状，从理论分析、系统仿真、硬件设计、软件设计和实验验证等方面展开研究，设计了基于阻抗实部测量法的信号拾取系统。 基于电感耦合理论，从阅读天线和LC谐振式无线压力传感器耦合模型的等效阻抗出发，对相位测量法、阻抗实部测量法、S11测...In harsh environment such as high temperature and humidity, or applications like intraocular pressure measurement and scar treatment it’s difficult to detect with wired and active sensors. LC resonant pressure sensor expands the application range of the pressure sensor by measuring pressure in a wireless and passive way. At present, The signal pickup instrument for the wireless passive LC resonant...学位：工学硕士院系专业：航空航天学院_机械电子工程学号：1992013115288

WIRELESS IMPLANTABLE MAGNETOELASTIC SENSORS AND ACTUATORS FOR BIOMEDICAL APPLICATIONS

Magnetoelastic sensors represent a low-cost wireless and battery-less method for monitoring parameters in embedded or implanted applications; however, some limitations still exist preventing their commercial implementation. Presented in this work are a variety of studies that are aimed at improving the feasibility of magnetoelastic materials for sensing and actuating applications. Magnetoelastic resonant sensors of non-standard geometries were investigated to determine if geometry could play a role on the sensitivity of the sensor response to mass loading. It was shown that a significant increase in sensitivity could be achieved by using triangular sensors rather than standard rectangular strips. A method for monitoring multiple parameters on a single magnetoelastic resonant strip was also pursued. It was demonstrated that multiple parameters will have different effects depending on the location of the applied load due to the effect of sensor areas with zero vibration at different harmonics of the fundamental resonant frequency. Magneto-harmonic sensors and actuators were also explored in this work. Specifically, it was demonstrated that magnetoelastic sensors could be implemented as a means of detecting stresses on deep tissue wounds, which are critical for proper healing of certain wound sites after surgery. Both a suture and a suture anchor design were investigated for their efficacy at monitoring forces applied to tendon repair sites. Two detection devices were fabricated and built for this work which represent low-cost alternatives (both less than $200 each) to commercially available alternatives that minimally cost tens of thousands of dollars. This advancement reinforces the claim that magnetoelastic materials are a low-cost and portable sensing solution. The biodegradability and cytotoxicity of a promising magnetoelastic material for biomedical applications, specifically Galfenol (iron-gallium), was also investigated. Cytotoxicity tests demonstrated that concentrations much higher than would be likely to be encountered in vivo are necessary to cause significant cellular toxicity. Additionally, surface characterization of the degraded materials suggests that the degradation rate of Galfenol can be wirelessly controlled through application of externally applie

Development of Position-Dependent Luminescent Sensors: Spectral Rulers and Chemical Sensing Through Tissue

Assessing the performance of medical devices is critical for understanding device function and monitoring pathologies. With the use of a smart device clinically relevant chemical and mechanical information regarding fracture healing may be deduced. For example, strain on the device may be used as a mechanical indicator of weight-bearing capacity. In addition, changes in chemical environment may indicate the development of implant associated infections. Although optical methods are widely used for ex vivostrain/motion analysis and for chemical analyses in cells and histological tissue sections, there utility is limited through thick tissue because light scattering reduces spatial resolution. This dissertation presents four novel luminescent sensors that overcome this limitation. The sensors are capable of detecting chemical and physical changes by measuring position or orientation-dependent color/wavelength changes through tissue. The first three sensors are spectral rulers comprised of two patterned thin films: an encoder strip and an analyzer mask. The encoder strip is either a thin film patterned with stripes of alternating luminescent materials (quantum dots, particles or dyes) or a film containing alternating stripes of a dye that absorbs luminescence from a particle film placed below. The analyzer mask is patterned with a series of alternating transparent windows and opaque stripes equal in width to the encoder lines. The analyzer is overlaid upon the encoder strip such that displacement of the encoder relative to the analyzer modulates the color/spectrum visible through the windows. Relative displacement of the sensor layers is mechanically confined to a single axis. When the substrates are overlaid in the “home position” one line spectrum is observed, and in the “end position,” another line spectrum is observed. At intermediate positions, spectra are a linear combination of the “home” and “end” spectra. The position-modulated signal is collected by a spectrometer and a spectral intensity ratio from closely spaced emission peaks is calculated. By collecting luminescent spectra, rather than imaging the device surface, the sensors eliminate the need to spatially resolve small features through tissue by measuring displacement as a function of color. We measured micron scale displacements through at least 6 mm of tissue using three types of spectral ruler based upon 1) fluorescence, 2) x-ray excited optical luminescence (XEOL), and 3) near infrared upconversion luminescence. The sensors may be used to investigate strain on orthopedic implants, study interfragmentary motion, or assess tendon/ligament tears. In addition to monitoring mechanical strain it is important to investigate clinically relevant implant pathologies such as infection. To address this application, we have developed a fourth type of sensor. The sensor monitors changes in local pH, an indicator of biofilm formation, and uses magnetic fields to modulate position and orientation-dependent luminescence. This modulation allows the sensor signal to be separated from background tissue autofluorescence for spectrochemical sensing. This final sensor variation contains a cylindrical magnet with a fluorescent pH indicating surface on one side and a mask on the other. When the pH indicating surface is oriented towards the collection optics, the spectrum generated contains both the sensor and autofluorescence signals. Conversely, when the pH sensor is oriented away, the collected signal is composed solely of background signals. All four of the sensors described can be used to build smart devices for monitoring pathologies through tissue. Future work will include the application of the strain and chemical sensors in vivo and ex vivo in animal and cadaveric models

Método para identificar simultaneamente duas características elétricas moduláveis por parâmetros fisiológicos de microcircuitos RLC injetáveis

This work proposes a biotelemetric method to determine simultaneously two electrical characteristics (modulated by physiological parameters) from a passive injectable RLC microcircuit. Due to the presence of free ions inside the biological tissue, inductive links (loop antennas) must be employed, instead of dipole antennas. As the coil of the sensor presents small dimensions (diameter of about mm) its magnetic coupling to the monitoring device requires special attention. To monitor the sensor, a digital device assembled with a group of coils to maximize the mutual inductance (at a distance of 5 mm) between them was developed, detecting its resonance frequencies and the respective amplitude (through a frequency sweep) in real-time. The electrical response acquired by the detector from the sensor was analytically modeled. The model indicates a time constant to consider for each change of the signal frequencies to prevent errors in the response. From that theoretical model, an equation to determine the total resistance from the RLC circuit was obtained and confirmed by experiments. Then, a method to determine the resonance frequency and the total resistance from remote RLC circuit was proposed. A sensor was developed to verify the accuracy and the limits from this method. A parallel RLC circuit was built inside a silicone rubber tube. When the tube is stretched, a ferrite rod assembled beside the inductor is displaced varying the resonance frequency and, changing the environmental temperature, a NTC varies the quality factor of the circuit. Tests using the proposed method to monitor the sensor were realized. Errors small than 0.57 % in the resonance frequencies and 0.77 % in the temperature were obtained. The measured influence of the temperature variation over frequency determination was less than 0.16 %, indicating that the method is feasible.Este trabalho propõe um método biotelemétrico para a determinação simultânea de duas características elétricas (moduláveis por parâmetros fisiológicos) de circuitos RLC passivos para microsensores injetáveis. Como o ambiente sob monitoração envolve a presença de íons (tecidos biológicos), a utilização de dipolos torna-se inviável, desta forma, o estabelecimento de um acoplamento indutivo entre o sensor e o dispositivo para o registro das medidas é necessário. Tratando-se de um dispositivo injetável, as dimensões da bobina do sensor são diminutas (diâmetro da ordem de mm), sugerindo cuidados especiais quanto ao acoplamento indutivo do circuito RLC com o dispositivo de registro das medidas. Desta forma, foi desenvolvido um detector digital de freqüências, associado a um conjunto otimizado de bobinas para obter, a determinada distância (5 mm), a melhor indutância mútua possível com o microcircuito RLC remoto. Este dispositivo monitora o sensor em tempo real, informando a freqüência de ressonância, a sua respectiva amplitude a partir de uma varredura em freqüência. Um estudo analítico modelando a resposta em tensão do circuito detector segundo os estímulos e respostas que este fornece e recebe do circuito RLC remoto foi desenvolvido. O resultado desta análise, verificada praticamente, possibilitou a identificação da constante de tempo que cada degrau de freqüência deve ser mantido no sensor para que a resposta indicada seja a mais precisa possível. Decorrente desta análise foi possível modelar teoricamente a resistência total que o circuito RLC remoto apresenta. Assim, a partir das medidas de freqüência e amplitude do detector e do modelo teórico da resistência total do sensor o método foi estabelecido. Para verificar na prática a validade do método um micro sensor (2,8 x 23 mm) foi desenvolvido. O sensor foi encapsulado dentro de um tubo de silicone, apresentando um indutor montado junto a um bastão de ferrite, um capacitor SMD e um NTC, todos associados em paralelo. Com a alteração da distância entre o bastão de ferrite e o indutor (através da tração do tubo de silicone) a freqüência do sensor é alterada e a variação da resistência do NTC, através da temperatura, altera o fator de qualidade do sensor. A utilização do método para monitorar o sensor apresentou erros inferiores a 0,57 % para a indicação da freqüência e 0,77 % para a indicação da temperatura. A influência medida da variação da temperatura sobre a indicação da freqüência foi inferior a 0,16 %, indicando que o método é viável

Aerospace medicine and biology - a continuing bibliography, july 1965

Annotated bibliography on aerospace medicine and biolog