Employing Convective Assembly for Micro-/Nano-Fabrication of Colloidal Crystals

采用对流组装进行胶体晶体的微/纳米制造

• 批准号: 0726958
• 负责人: Jeffrey Derby
• 金额: $ 35万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-15 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0726958&HistoricalAwards=false
• 关键词: Employing; Convective; Assembly; Micro; Nano

Weakly interacting colloidal particles, with uniform sizes ranging from several nanometers to microns, can spontaneously organize into close-packed crystals from concentrated liquid suspensions. Because they provide a simple, ordered structure with well-controlled and homogeneous porosity, these materials have been studied for many important applications, including sensing, separations,microfiltration, and batteries. A particularly interesting and promising application for colloidal crystals is their role for fabricating photonic crystals. These crystals exhibit a band gap for photons, namely there exists a range of photon frequencies inside the material for which light cannotpropagate in any direction. This property could be utilized to manipulate photons for novel optical circuits, biological and chemical sensors, and efficient thermal emission sources. To advance all of these applications, there is a need for an efficient, low-cost means to manufacture large quantitiesof high-quality colloidal crystals. Colloidal crystals have traditionally been made via the gentle sedimentation of spheres in a liquid suspension. This technique is ill-suited as a manufacturing process, since the settling rate is very slow, requiring months. If rushed, the resultant crystal is typically flawed by a significant amount of disorder. A process known as convective self-assembly can quickly, within hours, deposit colloidal particles into layers onto an inclined plate immersed within an evaporating liquid suspension.Surprisingly, these vigorously growing layers are characterized by a nearly perfect, face-centered cubic (fcc) crystalline structure, the equilibrium packing for this system. The fast growth rate and high material quality make convective assembly an attractive candidate for a manufacturingprocess for colloidal crystals. This research combines programs of computational modeling and experiments to understand the role of fluid flow and capillarity during the convective assembly of nanoscale, colloidal particles to form crystalline structures. Convective assembly processes have demonstrated greater production rates and higher material quality than achieved by classical particle settling methods. In this sense, capillarity and fluid motion coordinate a massive parallelization of particle interactions to achieve increases in production and quality; however, significant advances in understanding are neededto harness this process to achieve industrial-scale measures of production, reliability, robustness, yield, efficiency and cost. This understanding will be critical for the development of large-scale, nanomanufacturing processes.The societal benefits of this work will include the development of new approaches to nanomanufacturing, with longer-term benefits promised by the availability of nanoparticle-based crystalline materials that will impact applications for the environment, energy, and information technology.Broader activities include the education of undergraduate and graduate students in nanotechnology, as well as an outreach program for the general public involving the Science Museum of Minnesota.

弱相互作用的胶体颗粒，尺寸从几种纳米到微米不等，可以自发地组织成来自浓缩液体悬浮液的闭合晶体。 由于它们提供了一个简单，有序的结构，并具有良好的控制和均匀的孔隙度，因此已经研究了许多重要的应用，包括感应，分离，微滤过和电池。胶体晶体的一个特别有趣且有希望的应用是它们在制造光子晶体中的作用。这些晶体表现出光子的带隙，即在材料内部存在一系列光子频率，而光无法沿任何方向向光传播。该特性可用于操纵光子，以获取新型光学电路，生物学和化学传感器以及有效的热发射源。为了推进所有这些应用，需要有效，低成本的手段来制造高质量胶体晶体的大量。 传统上，胶体晶体是通过液体悬浮液中球体的轻轻沉降来制成的。该技术不适合作为制造过程，因为结算率非常慢，需要数月。如果匆匆忙忙，最终的晶体通常会因大量疾病而缺陷。一个称为对流自组装的过程可以在几个小时内迅速将胶体颗粒沉积到浸入蒸发液体悬浮液中的倾斜板上。显然，这些剧烈生长的层的特征是几乎完美的，以面部为中心的立方体（FCC）晶体结构，该系统的平衡包装。快速增长率和高材料质量使对流组件成为胶体晶体制造商的有吸引力的候选者。 这项研究结合了计算建模和实验程序，以了解纳米级对流组装过程中流体流和毛细血管的作用，胶体颗粒形成结晶结构。对流组装过程表明，与经典粒子沉降方法相比，对流组装过程表现出更高的生产率和更高的材料质量。从这个意义上讲，毛细血管和流体运动协调了粒子相互作用的大规模并行化，以提高生产和质量；但是，要利用这一过程来实现生产，可靠性，鲁棒性，收益率，效率和成本的工业规模的衡量，需要取得重大理解的进步。 This understanding will be critical for the development of large-scale, nanomanufacturing processes.The societal benefits of this work will include the development of new approaches to nanomanufacturing, with longer-term benefits promised by the availability of nanoparticle-based crystalline materials that will impact applications for the environment, energy, and information technology.Broader activities include the education of undergraduate and graduate students in nanotechnology, as well as an outreach program for the general public涉及明尼苏达州科学博物馆。