電子紙顯示技術的電動現象:低介電介質中的電泳動與電濕潤;Electrokinetic Phenomena of Electronic-Paper Display: Electrophoresis and Electrowetting in Low-Dielectric Constant Media

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Title:	電子紙顯示技術的電動現象:低介電介質中的電泳動與電濕潤;Electrokinetic Phenomena of Electronic-Paper Display: Electrophoresis and Electrowetting in Low-Dielectric Constant Media
Authors:	曹恒光
Contributors:	化學工程與材料工程學系
Keywords:	研究領域：化學工程類
Date:	2011-08-01
Issue Date:	2012-01-17 17:23:54 (UTC+8)
Publisher:	行政院國家科學委員會
Abstract:	隨著高科技產品逐漸走向輕、薄、短、小的市場趨勢，許多微觀尺度下的驅動系統便變得益發重要起來。而這些微系統又往往具有不同於一般巨觀尺度的行為模式。例如微流道、晶片上的微型實驗室、電泳顯示及電濕潤顯示等微觀驅動系統，在其運作過程中或多或少都會面臨工作流體或微粒子在溶劑中的電動問題，特別是以低介電常數溶劑做為介質時，更是無法避免的問題。在這些薄型化的科技產品中，又以電子紙這項兼節能環保且接近自然閱讀的技術最受到大家重視。在現行電子紙的顯示技術中又以電泳動技術、電濕潤技術較為普及成熟，具有較佳的應用性。而電泳動與電濕潤之間的共通點是皆會使用低介電常數的溶劑做為介質，再藉由外加電場方式，驅動工作粒子或流體進行電泳動或電濕潤之行為。在電泳動顯示技術中主要以微膠囊、微杯及電子粉流體三種系統為主流，都是使用低介電係數的溶劑做為泳動介質。一般而言，在低介電係數的介質環境下，由於強庫倫作用力的關係，介質中的工作粒子不易形成穩定的帶電狀態。但實際上，電泳式電子紙卻仍然可利用外加電場的方式驅動帶電粒子泳動。電泳的速度大小主要取決於外加電場強度、電解質溶液的介電常數、電解質溶液的黏度和帶電粒子表面電位強度等因素。因此在近乎不含離子且低介電係數介質的環境下，電子紙中的顯色微粒子如何進行電泳動，而其泳動速度以及所帶的電量及電性為何，在相關文獻中卻僅有少數的研究。基本上電子紙顯示技術的優劣與否主要取決於對比開關速率、影像解析度、影像對比、反射比、電能消秏及成本等因素。因此電子紙要邁向能夠取代傳統自發光顯示器的境界，其最重要的關鍵就在於對比開關速率的部分，也就是所謂的反應時間。因此不論是對電泳動或電濕潤技術，為了降低了其反應時間使其得以突破此一重大限制，朝向可應用於顯示器技術的領域邁進，對其電動現象的瞭解必然會是最為重要的關鍵所在。因此在這三年期的研究計劃中，我們將針對離子含量稀少的低介電常數溶劑系統，研究相關帶電微粒子在系統中的電泳動行為，藉此建立低介電常數環境中的電動現象之理論模型。除此之外，我們也將就電濕潤系統中油滴潤濕介電質材料表面的動態過程，研究相關表面性質對反應時間的影響；尤其希望藉著本實驗室在濕潤現象及其邊界效應方面的經驗，將其應用到電濕潤式的電子紙上，特別針對低介電常數的介質油滴與介電質材料，改善其動態反應所須時間。綜合以上，我們希望能利本實驗室在電動現象及界面科學方面的經驗與專長，結合理論計算、分子模擬及實驗設計方面的優勢，配合毛細管電泳動、動態光散射法、動態接觸角量測系統、高速變焦顯微鏡系統等實驗方法與設備，針對電子紙的電動現象進行更深入的探討，建構出更為完備的物理模型，以提供國內產業未來開發與改良相關顯示技術的理論基礎。 Since high-tech products are gradually made in a way to achieve the requirements of light weight, thin, short, and small size, many microscale driving systems become important. The examples include microchannel, lab-on-a-chip, electrophoretic display and electrowetting display. However, the behaviors of these micro-systems are significantly different from those of typical macro-systems. In their operating processes, the working fluid and colloidal particles in solvent often results in problems associated with electrokinetic phenomena, especially when solvents with low dielectric constant are used as media. The electronic paper, owning characteristics of energy saving and natural reading, is regarded as one of the most important technology. For such display technology, electrophoresis and electrowetting come to maturity and have better practical applications. The resemblance between electrophoresis and electrowetting is that both of them can use solvent with low dielectric constant as medium and drive working fluid or particle to move by applying external electric field. Microcapsulation, microcup and liquid powder display are currently the three major approaches for electrophoresis display technology and all of them use solvent with low dielectric constant as electrophoresis medium. In such media, it is not easy for working particles to carry charges due to strong Coulombic interaction. For aqueous solutions, the dielectric constant is high and the electrophoretic velocity is known to depend on the intensity of external electric field, surface potential of charged particle, dielectric constant and viscosity of electrolyte solution. For media with low dielectric constant, the relevant studies are scarce in literature. It is essential to understand why colloidal particles (dye) in electric paper can carry charges and thus migrate in a nearly ion-free medium with low dielectric constant. The performance of electronic paper depends on velocity of contrast switch, image resolution, image contrast, reflection ratio, electric energy consumption and cost, etc. However, in order for electronic paper to prevail over traditional self-luminous displays, the key issue is the velocity of contrast switch, so-called response time. For electrophoresis and electrowetting display technology, the reduction of the response time is the bottleneck and therefore the underlying electrokinetic phenomena play the key role. In this three years’ project, we will focus on the system with nearly ion-free solvent due to its low dielectric constant and try to establish theoretical models of electrokinetic phenomena in electrophoresis E-paper. In addition, we will study the influence of surface property of the substrate on the response time associated with an oil droplet wetting the dielectric materials in electrowetting E-paper. We shall apply our expertise of wetting phenomena to the improvement of the response time of oil medium with low dielectric constant on interfacial dielectric substrate. Our approaches include theoretical and experimental studies. The theoretical studies consist of the continuum approaches (solving the nonlinear Poisson-Boltzmann equation and Stokes equation, SPHysics, Surface Evolver) and molecular simulations (Brownian Dynamics). The experimental studies include capillary electrophoresis, dynamic light scattering & zeta-potential analysis, interfacial properties measurement, dynamic contact angle measurement, and high-speed zoom lens microscope system. The goal of this project is to establish a sound physical model of electrokinetic phenomena, which provides useful guidelines for the development and improvement of E-paper display technology. 研究期間：10008 ~ 10107
Relation:	財團法人國家實驗研究院科技政策研究與資訊中心
Appears in Collections:	[Department of Chemical and Materials Engineering] Research Project

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