Photocatalytic Active Matter

活性物质是由能将能量转化为运动的粒子组成的物质。 活跃物质的例子有鱼群、鸟群和细菌。 大多数活性物质的例子都是生物起源的，但目前有大量的研究是合成系统。这个概念是感兴趣的，因为可控和可逆的组装较大的结构，触发捕获，交付和释放货物，如药物，并使用它作为一种工具，了解生物过程是不平衡的潜力。 该提案旨在确定和开发用于移动和操纵流体中纳米至微米尺寸的活性颗粒的方法。例如，活性球形颗粒可以通过在一个半球上涂覆一种化学物质来产生，该化学物质可以与溶解在流体中的另一种化合物反应。由于未涂覆的半球是惰性的，因此颗粒具有与溶解的化学品的不同浓度相关的优选运动方向。然而，像这样的系统不容易打开和关闭;如果燃料存在，颗粒仍然活跃和移动。该研究项目正在探索一种可以通过光照明来打开和关闭的新系统。特殊的制造方法被用来生产具有复杂形状的光激活粒子，以确定形状在活性粒子如何移动和组装成更大结构中的作用。这个研究项目的显着特点是，研究生和本科生都深入参与研究，研究的各个方面正在纳入本科实验室类。 参与该项目的研究人员正在将项目相关的演示带到位于亚利桑那州北方霍皮保留区的霍皮高中，以吸引在STEM领域代表性不足的学生参与科学。活性胶体最近受到了相当大的关注，但关于运动和粒子自组装机制的一些问题仍然没有答案。此外，功能性纳米机器的实现，例如用于货物运输，仍处于起步阶段。该研究项目旨在研究一种光催化活性系统，其中活性可以很容易地打开和关闭。基于掠射角沉积（GLAD）的专业制造技术正被用于生产具有复杂形状和材料成分的活性胶体颗粒。这些各向异性粒子被用来深入了解如何控制粒子运动，并研究形状在粒子自组装中的作用。这种由各种形状的光催化活性颗粒组成的系统可能会使新的应用成为可能，并使人们对纳米尺度的推进力有更深入的了解。最终，研究人员打算利用这些活性粒子的自组装来控制中尺度货物的拾取和释放。该研究项目还包括一个重要的教育和推广组成部分，包括开发基于纳米科学的课程，本科实验室课程的新实验模块，以及来自亚利桑那州北方的美洲原住民学生的参与。

Active matter is matter composed of particles that can convert energy into motion. Examples of active matter are schools of fish, flocks of birds, and bacteria. Most examples of active matter are biological in origin, but presently there is a significant amount of research into synthetic systems. This concept is of interest because of the potential for controllable and reversible assembly of larger structures, for the triggered capture, delivery, and release of cargo such as drugs, and for using it as a tool for understanding biological processes that are out of equilibrium. This proposal aims to identify and develop methods for moving and manipulating nanometer-to-micron sized active particles in fluids. For example, active spherical particles can be produced by coating one hemisphere with a chemical that can react with another compound dissolved in the fluid. Since the uncoated hemisphere is inert, the particle has a preferred direction of motion related to the varying concentration of the dissolved chemical. However, systems such as this cannot easily be switched on and off; if the fuel is present, the particles remain active and moving. This research project is exploring a novel system that can be switched on and off through illumination by light. Special fabrication methods are being used to produce light-activated particles with complex shapes in order to identify the role shape has in how active particles move and assemble into larger structures. Significant features of this research project are that both graduate and undergraduate students are deeply involved in the research and that aspects of the research are being incorporated into an undergraduate laboratory class. The researchers involved in this project are bringing project-related demonstrations to Hopi High School on the Hopi Reservation in Northern Arizona in an effort to engage students in science who are underrepresented in STEM fields. Active colloids have received considerable attention recently, but a number of questions remain unanswered regarding the mechanisms of motion and particle self-assembly. In addition, the realization of functional nanomachines, for example for cargo delivery, is still in its infancy. This research project aims to study a photocatalytically active system, in which the activity may be easily switched on and off. Specialized fabrication techniques, based on glancing angle deposition (GLAD), are being used to produce active colloidal particles with complex shapes and material compositions. These anisotropic particles are being used to gain insight into how to control particle motion and to investigate the role of shape in self-assembly of the particles. This system of photocatalytic active particles of various shapes may make possible new applications and a deeper understanding of propulsion at the nanoscale. Ultimately, the researchers intend to control the pick-up and release of cargo at the mesoscale using the self-assembly of these active particles. The research project also includes a significant educational and outreach component, including the development of a nanoscience based course, a new experimental module for an undergraduate lab course, and the involvement of Native American students from Northern Arizona.