【摘要】：腦積水是一種在嬰幼兒和老年人群中常見的疾病,其病因在于腦脊液分泌過多或(和)循環(huán)、吸收障礙引起顱內(nèi)壓的增高,因而導(dǎo)致頭顱增大、頭痛、智力障礙等。目前,腦積水治療手段主要采用腦室腹腔分流術(shù),通過在病人體內(nèi)植入分流閥系統(tǒng),將過多的腦脊液引流到腹腔中被吸收掉,從而使腦顱壓保持在正常范圍內(nèi);但該分流閥系統(tǒng)故障率較高,容易發(fā)生阻塞、過引流或者引流不足等問題,嚴(yán)重威脅病人的生命安全。目前,主要通過CT或MRI來輔助調(diào)整閥門大小,但該方法存在測量精度較差、成本較高且無法實現(xiàn)連續(xù)測量等缺點。針對以上不足,本文以基于聲表面波原理的腦顱壓傳感器為研究對象,通過傳感器理論建模和有限元仿真等手段,對傳感器的溫度補償策略、結(jié)構(gòu)設(shè)計方法及加工工藝等關(guān)鍵技術(shù)進(jìn)行深入研究,實現(xiàn)對腦顱壓的低成本連續(xù)測量功能。針對腦顱壓傳感器溫度漂移問題,本文設(shè)計了基于ST切型石英基底的差分式腦顱壓傳感器結(jié)構(gòu)。由于ST切型石英具有良好的溫度穩(wěn)定性,本文將其作為傳感器的壓電基底,通過在上表面蒸鍍鋁電構(gòu)成叉指換能器和反射柵,設(shè)計了諧振器型結(jié)構(gòu)。本文提出了一種將經(jīng)驗公式與耦合數(shù)學(xué)模型相結(jié)合的局部快速仿真?zhèn)鞲衅鹘Y(jié)構(gòu)參數(shù)的方法,提高了傳感器設(shè)計效率。首先,利用經(jīng)驗公式對傳感器的結(jié)構(gòu)參數(shù)進(jìn)行初始設(shè)計,確定其主要取值范圍。然后,通過建立傳感器耦合數(shù)學(xué)模型,更精確地實現(xiàn)仿真設(shè)計。以傳感器S散射參數(shù)幅值為目標(biāo),通過研究傳感器的電極指條對數(shù)、膜厚比等參數(shù)變化規(guī)律并進(jìn)行設(shè)計,得到了Q值較高的器件。最后,通過設(shè)計雙諧振器型結(jié)構(gòu),對傳感器進(jìn)行差分補償,改善了傳感器的溫度特性。對傳感器進(jìn)行了相關(guān)實驗,測得精度約為3.21%,達(dá)到了本文所提出的設(shè)計目標(biāo)。由于ST切型石英基底機(jī)電耦合系數(shù)較小,本文利用不同材料溫度系數(shù)相反的特性,通過在128°YX切型Li Nb O3壓電基底上蒸鍍Si O2薄膜,設(shè)計了一種多層膜結(jié)構(gòu)的新型傳感器,它具有較大機(jī)電耦合系數(shù)和良好溫度穩(wěn)定性。首先,建立傳感器有限元仿真模型,利用特征頻率分析,計算聲表面波在壓電基底材料上的傳播速度。分析了在不同Si O2薄膜厚度下,機(jī)電耦合系數(shù)的變化規(guī)律。其次,通過將溫度場耦合到仿真模型中,計算不同溫度下聲表面波傳播速度,研究了多層膜結(jié)構(gòu)Si O2膜厚與溫度系數(shù)變化規(guī)律。確定多層膜結(jié)構(gòu)零溫度系數(shù)對應(yīng)的Si O2鍍膜厚度及機(jī)電耦合系數(shù)大小。最后,通過頻域仿真,得到了多層膜結(jié)構(gòu)傳感器的S參數(shù),并對器件進(jìn)行了靜態(tài)實驗測試和驗證,該多層膜結(jié)構(gòu)測得的機(jī)電耦合系數(shù)遠(yuǎn)大于石英晶體。通過研究MEMS加工工藝,制作了傳感器樣機(jī)。利用干法刻蝕工藝,在壓電基底上制作叉指和反射柵電極結(jié)構(gòu)。針對PECVD蒸鍍較大厚度Si O2薄膜熱應(yīng)力問題,通過改進(jìn)工藝流程,采用分時鍍膜釋放熱應(yīng)力的方法,解決了較大膜厚下Si O2表面出現(xiàn)破裂的問題。為了減小傳感器尺寸并提高靈敏度,設(shè)計合金膜片式傳力結(jié)構(gòu)。但由于工藝達(dá)水平的局限性,導(dǎo)致該方法制作的傳感器重復(fù)性一般。為了解決這一不足,研制了壓電敏感元件直接受壓的“三明治”式封裝結(jié)構(gòu),有效地改善了傳感器的重復(fù)性。搭建了傳感器實驗測試系統(tǒng)。采用0.01%精度的硅諧振傳感器作為基準(zhǔn),通過Mensor壓力控制器和恒溫箱分別控制壓力和溫度輸出,對傳感器的壓力和溫度特性進(jìn)行實驗研究,驗證了溫度補償方案的可行性。本文提出的聲表面波腦顱壓傳感器,實現(xiàn)了基本壓力參數(shù)的測量功能,解決了現(xiàn)有腦顱壓測量精度不高或不能連續(xù)測量等問題,后續(xù)設(shè)計天線能夠?qū)崿F(xiàn)無源無線測量。通過設(shè)計傳感器的量程,也可以將其擴(kuò)展到心臟血壓等其它生理參數(shù)的測量,本文的研究成果在臨床應(yīng)用方面具有潛在的重要價值。
[Abstract]:Hydrocephalus is a common disease in infants and the elderly, the cause of which is the excessive or (and) circulation of the cerebrospinal fluid, which causes an increase in the intracranial pressure, resulting in an increase in the head, a headache, an intellectual disorder, and the like. At present, the method for treating the hydrocephalus mainly adopts a ventriculoperitoneal shunt, and the through-flow valve system is implanted in the patient, the excessive cerebrospinal fluid is drained into the abdominal cavity to be absorbed, so that the cranial pressure is kept in a normal range, the fault rate of the shunt valve system is high, the blockage is easy to occur, the problems of over-drainage or underdrainage and the like are serious, and the life safety of the patients is seriously threatened. At present, the size of the valve is mainly assisted by CT or MRI, but the method has the disadvantages of poor measurement precision, high cost and no continuous measurement. In view of the above shortcomings, this paper makes an in-depth study on the temperature compensation strategy, structural design method and processing technology of the sensor by means of sensor theory modeling and finite element simulation, based on the theory of surface acoustic wave, as the research object. and the low-cost continuous measurement function of the brain intracranial pressure is realized. In order to solve the problem of the temperature drift of the brain-cranial pressure sensor, the structure of the differential type brain-cranial pressure sensor based on the ST-cut quartz substrate is designed. As the ST-cut quartz has good temperature stability, the piezoelectric substrate of the sensor is used as the piezoelectric substrate of the sensor, and the interdigital transducer and the reflecting grating are formed by vapor-plating on the upper surface, and the resonator type structure is designed. In this paper, a method of combining the empirical formula with the coupled mathematical model is proposed, and the design efficiency of the sensor is improved. First, using the empirical formula, the structural parameters of the sensor are initially designed and the main value range is determined. and then the simulation design is realized more accurately by establishing a sensor coupling mathematical model. With the sensor S scattering parameter amplitude as the target, the parameters of the parameters such as the logarithm of the electrode finger of the sensor and the thickness ratio of the film were studied and the design was carried out to obtain the device with higher Q value. Finally, by designing the double-resonator type structure, the differential compensation of the sensor is carried out, and the temperature characteristic of the sensor is improved. The relative experiment of the sensor is carried out, the accuracy of the measurement is about 3.21%, and the design goal set forth in this paper is achieved. Because the electromechanical coupling coefficient of the ST-cut type quartz substrate is small, a new type of sensor for multi-layer film structure is designed by vapor-plating the Si O2 thin film on a 128-degree YX-cut Li Nb O3 piezoelectric substrate by using the characteristics of the opposite of the temperature coefficient of different materials. It has a large electromechanical coupling coefficient and good temperature stability. First, a finite element simulation model of the sensor is established, and the propagation velocity of the surface acoustic wave on the piezoelectric substrate material is calculated by using the characteristic frequency analysis. The change law of the electromechanical coupling coefficient under the different thickness of different Si _ 2 films is analyzed. Secondly, by coupling the temperature field to the simulation model, the propagation velocity of the surface acoustic wave at different temperatures is calculated, and the change law of the film thickness and the temperature coefficient of the multi-layer film structure Si O2 is studied. and determining the thickness of the Si _ 2 film and the size of the electromechanical coupling coefficient corresponding to the zero-temperature coefficient of the multi-layer film structure. Finally, the S parameters of the multi-layer film structure sensor are obtained by frequency domain simulation, and the static test and verification of the device are carried out, and the electromechanical coupling coefficient measured by the multilayer film structure is much larger than that of the quartz crystal. The sensor prototype was fabricated by studying the MEMS processing technology. By using the dry etching process, the interdigital and reflective gate electrode structures are fabricated on the piezoelectric substrate. In order to solve the thermal stress problem of the large-thickness Si _ 2 thin film by PECVD, the problem of cracking of the surface of the Si _ 2 under the thick film thickness is solved by improving the process flow and using the method of releasing the thermal stress at the time of separation. in ord to reduce that size of the sensor and improve the sensitivity, an alloy diaphragm type force-transfer structure is designed. but due to the limitation of the process level, the sensor repeatability produced by the method is generally. In order to solve this deficiency, the 鈥渟andwich鈥，

本文編號：2383732