基于离子液体的医用加速度传感器的研究

发布时间：2018-11-28 13:42

【摘要】：加速度传感器是生产、生活中广泛使用的一种测量加速力大小的电子器件。一般由惯性质量块、阻尼元件、弹性元件、敏感元件和调试电路组成。在加速运动过程中,传感器对质量块所受到的惯性力进行测量,后根据牛顿第二定律获得加速度值。在生物医疗领域,加速度传感器可用于手术导航系统、心肺复苏设备、残疾病人康复治疗等。受人耳前庭系统中椭圆囊/球囊检测线性加速度运动信号机制的启发,本课题设计了适用于检测人体微弱、低频运动信号的离子液体加速度传感器。从结构设计、材料选型、检测原理及性能表征四个方面进行了研究。使用性能良好的绿色电解液,室温离子液体(Room temperature ionic liquids,ILs)代替传统电解质溶液,作为液态惯性质量块,聚甲基丙烯酸甲酯(PMMA)作为基底及封装材料,物理化学性能稳定且具有大比表面积的活性炭纸为检测电极,制备出尺寸为2×2×5 mm3的加速度传感器。建立了离子液体加速度传感器内部微液体运动模型及固-液界面双电层(Electrical double layer,EDL)电学检测模型,液体运动使电解液与电极的接触面积发生变化,改变固-液接触面EDL电容值。使用有限元方法,通过建立3D微液体运动和1D双电层两个模型验证了液体体积、粘度和固-液接触角对液体的运动延迟和幅度均有影响。固-液界面EDL结构中,根据电极端施加的直流电压,阴阳离子浓度和电荷密度呈规律分布,且随电压增大,电极表面的电荷浓度和密度增加。分别制备了单惯性体和多惯性体两种结构加速度传感器,当外界激励频率f=6.89 Hz,运动位移x=40 mm时,在未加信号处理模块的情况下,单惯性体加速度传感器灵敏度Sn=0.689 mV/g。在2.5 Hz-11.75 Hz频率范围内,固定ILs加速度传感器运动位移x=40 mm时,器件谐振频率fres=7.13 Hz,此时输出信号Vp-p=10.2 mV,但在测试过程中,3 dB带宽为~2.5 Hz,带宽较窄,限制了传感器的实际应用。相同运动激励下,相比单惯性体结构,多惯性体传感器灵敏度Sn=1 mV/g,灵敏度提升了45%。将多惯性体结构传感器与商用加速度计ADXL335对比分析,离子液体加速度传感器在未进行信号放大的前提下,表现出与商用传感器一样的效果,但其输出信号的信噪比要低于ADXL335。使用多惯性体结构传感器能够清晰识别出手臂在低频3.6 Hz、6.2 Hz的运动状态,表明该加速度传感器有望应用于人体运动等低频、微弱的信号检测中。
[Abstract]:Acceleration sensor is a kind of electronic device which is widely used in production and life to measure acceleration force. Generally consists of inertia mass block, damping element, elastic element, sensitive element and debugging circuit. In the process of acceleration, the sensor measures the inertia force of the mass block, and then obtains the acceleration value according to Newton's second law. In the biomedical field, accelerometers can be used in surgical navigation systems, cardiopulmonary resuscitation equipment, rehabilitation of disabled patients, etc. Inspired by the mechanism of elliptical sac / balloon detection of linear acceleration signal in human ear vestibular system, an ionic liquid acceleration sensor suitable for detecting weak and low frequency motion signals of human body is designed in this paper. The structure design, material selection, testing principle and performance characterization are studied. Using green electrolyte with good performance, room temperature ionic liquid (Room temperature ionic liquids,ILs) instead of traditional electrolyte solution, as liquid inertial mass block, polymethyl methacrylate (PMMA) as substrate and packaging material. An accelerometer with a size of 2 脳 2 脳 5 mm3 was prepared by using activated carbon paper with stable physical and chemical properties and large specific surface area as the detection electrode. The internal microliquid motion model of ionic liquid accelerometer and the electrical detection model of solid-liquid interface double electric layer (Electrical double layer,EDL) were established. The contact area between electrolyte and electrode was changed by liquid movement. The EDL capacitance of solid-liquid interface is changed. By using the finite element method, the effects of liquid volume, viscosity and solid-liquid contact angle on the motion delay and amplitude of the liquid were verified by establishing 3D microliquid motion model and 1D double electric layer model. In the solid-liquid interface EDL structure, according to the DC voltage applied by the electric extreme, the concentration and the charge density of the anion and anion show a regular distribution, and with the increase of the voltage, the charge concentration and density on the electrode surface increase. Two kinds of accelerometers, single inertial body and multiple inertial body, were fabricated respectively. When the external excitation frequency fr 6.89 Hz, moving displacement x 40 mm, without the signal processing module, Single Inertial body acceleration Sensor sensitivity Sn=0.689 mV/g. In the range of 2.5 Hz-11.75 Hz frequency, when the displacement of the ILs accelerometer is fixed x 40 mm, the resonant frequency of the device fres=7.13 Hz, outputs the signal Vp-p=10.2 mV, at this time. But in the testing process, the 3 dB bandwidth is ~ 2.5 Hz,. The narrow bandwidth limits the practical application of the sensor. Under the same motion excitation, the sensitivity Sn=1 mV/g, sensitivity of the multi-inertial body sensor is 45% higher than that of the single inertial body structure. By comparing the multi-inertial structure sensor with the commercial accelerometer ADXL335, the results show that the ionic liquid accelerometer has the same effect as the commercial sensor without signal amplification, but the signal-to-noise ratio of the output signal is lower than that of the ADXL335.. The motion state of the arm at low frequency 3.6 Hz,6.2 Hz can be clearly identified by using the multi-inertial body structure sensor, which indicates that the accelerometer is expected to be used in the detection of low frequency and weak signals such as human motion.
【学位授予单位】：深圳大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R318.6;TP212

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