Towards Intelligent Autonomous Nanoswimmers.

这项工作将结合两种明确定义和特征的物理效应，自扩散纳米游泳者（自我推进的纳米颗粒）和ph响应水凝胶，以产生一种新的纳米游泳者，它能够向化学识别的目标游泳，模仿活细胞的行为。它将首次展示完全合成的趋化性，并将成为未来软纳米技术设备的关键组成部分之一，同时作为一个非常简单的仿生模型，允许深入了解细胞趋化性行为。媒体经常把纳米技术描绘成一艘微型潜艇，在人体的动脉和静脉中航行。在这样的尺度上仔细观察物理定律意味着，纳米级潜艇在人体中滑行的想法，应该被它在不断被纳米级炮弹击中的同时，在糖浆状液体中挣扎所取代。在纳米尺度上，水的行为就像糖浆，即使是与单个水分子的碰撞也会产生影响。在自然界中，许多生物能够成功地在这种纳米尺度的环境中游泳。细菌，如大肠杆菌，有一个螺旋状的尾巴，它可以旋转以推动自己通过糖浆状的水。在寻找食物时，它们采用奔跑和翻滚的策略，长时间的直线运动被翻滚事件打断，它停止，旋转，然后开始向新的方向奔跑。如果这个方向是不利的，它停止，旋转，并再次运行。在纳米尺度上产生合成推进效应的一种简单方法是利用发生在纳米游泳器表面的化学反应，比如半涂有催化剂的球形颗粒。如果有合适的化学燃料，催化剂会分解燃料，产生局部的反应产物云，从而在球体上产生推进力。然而，他们游泳的方向是无法控制的。与周围液体分子的碰撞不仅会踢开粒子，还会使它们自旋。正是这种自旋导致被推进的粒子以一种随机的方式游动。然而，它旋转的速度与它的大小有关。物体越大，旋转越慢。这个研究项目将开发一种新型的纳米游泳者，它既能自主推进，也能自主转向。他们将以先前成功的纳米游泳者为基础，拥有半涂层催化剂表面，能够根据化学信号物理改变形状。如果纳米游泳者游向有利的化学信号，比如酸，它就会膨胀。通过这样做，它的旋转速度将大大降低，然后它将能够继续向化学信号游去。更具体地说，微球将使用经过验证的电喷涂技术生产，其中一半的微球将含有铂催化剂。这将是球体的推进部分。球体的另一半将由ph响应型聚电解质水凝胶制成。这种材料根据周围溶液的pH值膨胀和收缩。这种体积的转变，以及由此产生的旋转行为的改变，将被用来决定纳米游泳者推进自身的方向。也可能有聚合物凝胶对葡萄糖的反应表现出体积变化。这些将用于研究向高浓度葡萄糖方向游动的动物。这个令人兴奋的研究项目将由一名PDRA承担，他将受益于在这样一个刺激和冒险的研究领域的工作和培训。这项拨款将为未来的研究拨款申请及理论和实验研究提供跳板，同时也突显了本项目和整个纳米技术的跨学科性质。

This work will combine two clearly defined and characterised physical effects, self-diffusiophoretic nanoswimmers (self- propelled nanoparticles) and pH-responsive hydrogels, to produce a new class of nanoswimmers which are able to swim towards a chemically identified target, mimicking the behaviour of living cells. It will demonstrate for the first time a wholly synthetic version of chemotaxis and will be one of the key building blocks for the soft nanotechnology devices to come, whilst acting as a very simple biomimetic model allowing insight into cell chemotaxis behaviour.The media often presents the image of nanotechnology as a miniaturised submarine navigating through the arteries and veins of the human body. Closer inspections of the physical laws at such dimensions mean the idea of the nanoscale submarine gliding through the body, should be replaced with it struggling through a treacle-like liquid while being constantly hit by nanoscale cannon balls. At the nanoscale water behaves like treacle and a collision with even a single water molecule has an effect.In nature many organisms are able to swim through this nanoscale environment with great success. Bacteria, such as E.Coli, have a corkscrew-like tail which it rotates to push itself through the treacle-like water. In searching for food, they adopt a run and tumble strategy where long runs of straight motion are interrupted by tumbling event where it stops, rotates and then begins to run in a new direction. If this direction is unfavourable it stops, rotates, and runs again.A simple method for producing an synthetic propulsive effect at the nanoscale is to make use of chemical reactions taking place on the surface of a nanoswimmer, such as a spherical particle half coated with a catalyst. Given the right chemical fuel the catalyst will break down the fuel to produce a localised cloud of reaction products which generates a propulsive force on the sphere. However, there is no control over the direction in which they swim.Collisions with the surrounding liquid molecules not only kicks particles it also spins them. It is this spin which causes propelled particles to swim in a random fashion. However, the speed at which it spins is related to its size. The larger the object, the slower it rotates.This research project will develop a new class of nanoswimmers that are able to both propel and steer autonomously. They will be based upon previously successful nanoswimmers possessing a half coated catalyst surface that are able to physically change shape in response to a chemical signal. If the nanoswimmer swims towards a favourable chemical signal, i.e. an acid, it will expand. By doing so, its speed of rotation will be significantly reduced and it will then be able to continue to swim towards the chemical signal. More specifically, microspheres will be produced using the proven technique of electrospraying, where one half of the microsphere will contain the platinum catalyst. This will be the propulsive part of the sphere. The remaining half of the sphere will be made from a pH-responsive polyelectrolyte hydrogel. This material expands and collapses depending upon the pH of the surrounding solution. This volume transition, and hence change in rotational behaviour, will be used to determine the direction in which the nanoswimmer propels itself. It is also possible to have polymer gels which demonstrate a volume change in response to glucose. These will be used to investigate swimmer that steer towards high concentrations of glucose.This exciting research project will be undertaken by a PDRA who will benefit from working and training in such a stimulating and adventurous research area. This grant will form the springboard for future research grant applications and research avenues both theoretically and experimentally, whilst also highlighting the interdisciplinary nature of this project and nanotechnology as a whole.