| 查看: 504 | 回复: 0 | ||||
| 当前主题已经存档。 | ||||
chl5063木虫 (著名写手)
流浪在小木虫
|
[交流]
聚合物能够实现附着力的开关作用，Polymers get stuck into switchable adhesion
|
|||
|
【纳米科技世界快讯】据欧洲纳米技术网报道，"Geckel" glue has been busy grabbing the limelight, but it's not the only nanoscale adhesive making the headlines. Scientists in the UK and Germany have come up with an easy-to-make switchable formulation that could find its way into drug-delivery systems, nano-actuators and even shampoo. Nanotechweb.org speaks with Mark Geoghegan of Sheffield University's polymer centre and co-author of the textbook: Nanoscale Science and Technology, to find out more. How do you formulate your nano-adhesive and what makes it switchable? Our system consists of two main components – a polymeric gel and a 20 nm thick brush layer. The gel is made by simply sticking a monomer into a solution with cross-linker and a catalyst. The brush layer is a little more complicated to put together and is synthesised by atom transfer radical polymerisation. In other words, chemically modifying the surface and then adding a monomer, a catalyst and a ligand to the solution and stirring. This allows a "brush-like" polymer layer to be grown with one end attached to the silicon substrate, although the methodology is not restricted to silicon. Because we are dealing with charged polymers or polyelectrolytes, the adhesion can be switched "on" or "off" by simply changing the pH. In water, we have an attractive system that contains a positively charged brush layer and a negatively charged gel, which results in adhesion. At a pH of 2 the gel loses its charge and the plain Coulombic attraction goes, turning off the adhesion. Hydrogen bonding almost certainly contributes to the attractive force, but disentangling the roles of hydrogen bonding and Coulombic attractions is difficult. The joker in the pack is the Velcro effect. Forcing the gel and brush-coated surface together improves the adhesion. At low pressures we see the adhesion as being purely interfacial. However, when you press the two surfaces together at high pressures, it's possible that the brush's "bristles" get caught up in the mesh of the gel, rather like Velcro behaves. We need to investigate this effect further. Considering the strength, reversibility and scalability of your system, what do you see as the most promising uses for your polymer-based adhesive? In the paper we refer to fluidic systems where channels can be opened or closed by gates adhering to each other and detaching depending on pH. Polyelectrolyte brushes have been touted as nanoactuators for several years. Drug delivery is another candidate. The easy example is for drugs targeting the colon that need to survive the stomach, which is acidic, and then let go of their cargo in a different pH environment. Our method gives medical researchers another tool to consider. Personal care is another application that comes to mind. You would be surprised by the amount of technology that goes into shampoo and conditioner. Charged molecules play an important role here. The bottom line is that our technology is new and incredibly simple. I am convinced that it will find a use. How does your formulation compare with other nano nano-adhesives, such as last month's "geckel" glue? The "geckel" adhesive is a phenomenal example of what can be achieved with current technology. There have been other gecko-inspired adhesives, but the "geckel" version is nice because it works in water. The glue can be used thousands of times, although you need a means of physically removing it from the surface. Many of the uses for the "geckel" formulation apply to our switchable adhesive, but the real advantage of our technology is that it is very straightforward and can be controlled in situ. It is also easy to scale up. So far we've covered centimetre-sized areas with our switchable adhesive. The benefit of "geckel" glue over our technology is that it only makes requirements of one surface, whereas we need to control both components – the polyacid and the polybase. What are the next steps for you and your team? We need to improve and understand the technology. The pH differences are quite large – pH 1–2 is quite low for adhesion to be terminated – but this is something that we might be able to improve. Our next moves are scientific rather than technological as we need to investigate the role of the different bonding mechanisms. When we have a better feeling for the science, we'll be in a stronger position to direct the technology and gear-up for potential applications. The researchers presented their work in Angew. Chem. Int. Ed. 46 |
回复此楼» 收录本帖的淘帖专辑推荐
 高分子技术和理论 |
» 猜你喜欢
FileCode能看出啥？
已经有25人回复
-
关于Filecode分析方法
已经有11人回复
-
重要来源：本周末出结果
已经有9人回复
-
我的国基提前知道中了，可是同事的操作让我实在接受不了，怎么会有这样的人
已经有14人回复
-
结合人工智能，周易传统文化，filecode打分制来了，3分以上希望很大。
已经有4人回复
-
2019年青年基金涵评意见，大家看看几个A，几个B?
已经有11人回复
-
应该是93bebmhtak前后十一个字符比较关键
已经有36人回复
-
不应该看fileCode
已经有6人回复
-
好奇怪的filecode
已经有6人回复
-
filecode
已经有15人回复
» 本主题相关商家推荐: (我也要在这里推广)
