【摘要】：微/納顆粒的分離技術(shù)在生物、化學(xué)、微機(jī)械系統(tǒng)等領(lǐng)域有著廣泛的應(yīng)用。傳統(tǒng)的微/納分離方法有過(guò)濾、介電泳、磁性分離、光鑷子和超聲分離等。過(guò)濾分離方法不僅有著過(guò)濾介質(zhì)容易堵塞的問(wèn)題，而且用于微/納顆粒過(guò)濾的薄膜也比較貴，介電泳和磁性分離技術(shù)對(duì)于顆粒的性質(zhì)有一定帶電和帶磁的要求，光鑷子一次處理顆粒的量比較少，，而用超聲技術(shù)就可以避免以上幾種方法的不足。 本課題基于胡俊輝教授團(tuán)隊(duì)的研究基礎(chǔ)之上，提出了一種超聲換能器的新結(jié)構(gòu)，它能夠驅(qū)動(dòng)微小顆粒旋轉(zhuǎn)并達(dá)到分離效果。該超聲換能器是由兩塊鋁板夾著兩塊環(huán)形壓電陶瓷片用螺栓緊固而成，換能器的下鋁板處于彎扭組合振動(dòng)，用于顆粒的分離。為了激發(fā)出這種振動(dòng)模態(tài)，兩塊壓電片極化方向相反放置并加載交流電壓。實(shí)驗(yàn)中，我們用多普勒激光測(cè)振儀測(cè)量工作區(qū)域的振動(dòng)情況，所用到的實(shí)驗(yàn)顆粒是蝦籽、玻璃球和精鹽的兩兩混合物，實(shí)驗(yàn)觀察是在高速攝像機(jī)下進(jìn)行的。 實(shí)驗(yàn)發(fā)現(xiàn)，在鋁板的工作區(qū)域存在有局部的旋轉(zhuǎn)行波，這能夠很好地解釋顆粒在工作區(qū)域的旋轉(zhuǎn)現(xiàn)象。我們還發(fā)現(xiàn)在共振頻率下顆粒的分離效率最高，并且顆粒的旋轉(zhuǎn)速度和板的振動(dòng)幅值對(duì)分離效率也有影響。在相同時(shí)間內(nèi)的共振條件下，不同混合物的分離效率也是不同的，其中蝦籽和玻璃球的混合物分離效果最佳，蝦籽和精鹽的混合物分離效果其次，玻璃球和精鹽的混合物基本不能分離。我們還從理論上分析了影響分離效率的顆粒的特性，發(fā)現(xiàn)顆粒的密度，與板的摩擦因素和顆粒的法向變形量對(duì)分離效果有影響。 本課題的主要?jiǎng)?chuàng)新點(diǎn)在于提出了一種新的超聲換能器的結(jié)構(gòu)，這種結(jié)構(gòu)沒(méi)有旋轉(zhuǎn)主軸，能夠在空氣中利用工作板上的局部旋轉(zhuǎn)行波驅(qū)動(dòng)微小顆粒旋轉(zhuǎn)分離。
[Abstract]:The separation technology of micro / nano particles has been widely used in biology, chemistry, micro-mechanical system and so on. Traditional micro / nano separation methods include filtration, dielectric electrophoresis, magnetic separation, optical tweezers and ultrasonic separation. The method of filtration and separation not only has the problem of easy clogging in filtration media, but also the membrane used in micro/ nanocrystalline filtration is more expensive. Dielectric electrophoresis and magnetic separation technology have certain charge and magnetic requirements for the properties of particles. The amount of particles treated by optical tweezers at one time is less, but ultrasonic technique can avoid the shortcomings of these methods. Based on the research of Professor Hu Junhui's team, a new structure of ultrasonic transducer is proposed, which can drive the small particles to rotate and achieve the separation effect. The ultrasonic transducer is made of two aluminum plates clamped with two annular piezoelectric ceramic plates fastened by bolts. The lower aluminum plate of the transducer is in the bending-torsional combined vibration for the separation of particles. In order to excite this vibration mode, two piezoelectric plates are placed in opposite polarization direction and loaded with AC voltage. In the experiment, the vibration of the working area is measured by Doppler laser vibration instrument. The experimental particles are a mixture of shrimp seed, glass ball and refined salt, and the experimental observation is carried out under a high speed camera. It is found that there is a local rotating traveling wave in the working area of aluminum plate, which can explain the phenomenon of particle rotation in the working area. We also find that the separation efficiency of particles is the highest at resonance frequency, and the rotation speed of particles and the vibration amplitude of plate also affect the separation efficiency. At the same time, the separation efficiency of different mixtures is different, among which the mixture of shrimp seed and glass ball is the best, and the mixture of shrimp seed and refined salt is the second. The mixture of glass ball and refined salt can not be separated basically. We also theoretically analyze the characteristics of the particles which affect the separation efficiency. It is found that the density of the particles, the friction factors with the plate and the normal deformation of the particles have influence on the separation efficiency. The main innovation of this paper lies in the structure of a new ultrasonic transducer, which has no rotating spindle and can drive the rotating separation of tiny particles by using the local rotating traveling wave on the working plate in the air.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TB552

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本文編號(hào)：2299867