来自Rice University已经开发出一种新型的基于酸的溶剂，可防止碳纳米管缠结在一起时通常发生的意大利面条效应。
除了与常规制造工艺兼容外，溶剂还具有简化碳纳米管的处理，以使工业3D打印和滚动生产应用的规模扩大。
“There’s a growing realization that it’s probably not a good idea to increase the mining of copper and aluminum and nickel, said Matteo Pasquali, Professor of Chemical and Biomolecular Engineering, Chemistry and Material Science and Nanoengineering at Rice University. “But there is a giant opportunity to use hydrocarbons as our ore.
“In that light, we need to broaden as much as possible the range in which we can use carbon materials, especially where it can displace metals with a product that can be manufactured sustainably from a feedstock like hydrocarbons.”
3D打印碳纳米管
自1991年发现以来，碳纳米管被誉为比钢强，比钻石强，而导电比铜高1000倍。尽管研究提出了一系列潜在的重要意义industrial applications of carbon nanotubes, such as electronics and water purification filters, the technology is still very much in development.
目前，碳纳米管可用于开发复合材料然而，具有卓越的机械，热和导电性能，利用它们进行3D打印仍然带来重大挑战。
So far, carbon nanotube materials have been used to 3D print shape memory polymers for use insoft robotic applications，并且由于他们的生物相容性have also been used to3D打印组织支架.
In April last year, Arizona-based start-upMechnano在其研发中退出的隐身模式carbon nanotube technology for 3D printingmaterials with the launch of its electrostatic discharge (ESD) resin. The firm claims to be the first to have fabricated parts with carbon nanotubes using material jetting and vat photopolymerization systems, and believes its technology will bring “dramatic changes” to industries such as aerospace, defense, medical and automotive.
Untangling nanotube spaghetti
处理碳纳米管的挑战之一是它们对纠结的敏感性，当印刷作业出错时反映了可怕的“意大利面”效应，直到现在，这一直阻止研究人员意识到其全部潜力。
According to the Rice University team, separating the nanotubes is a necessary step before they can be extruded during 3D printing or where shear forces transform them into familiar fibers or sheets.
该团队开发了一种基于酸的溶剂，该溶剂有助于将溶液中的缠结纳米管分开，并将其变成具有出色的电气和机械性能的膜，纤维或其他材料。该溶剂由酸的独特组合，即甲烷硫酸盐（MSA），P-苯二烯硫酸盐（PTOS）和oleum酸组成，当组合时，其腐蚀性不如当前在纳米管处理中使用的腐蚀性较低。
含油酸和氯磺酸已被用来分离纳米管一段时间，但是具有高度腐蚀性。将油脂与较弱的MSA和PTOS酸相结合，使得创建了广泛适用的过程，从而为碳纳米管零件提供了新的制造机会。
“The oleum surrounds each individual nanotube and gives it a very localized positive charge,” said Robert Headrick, a graduate alumnus of Rice University involved in the study and current Research Scientist at Shell. “That charge makes them repel each other.”
纠缠在舞台后,MSA和美国专利商标局酸further separate the nanotubes. The researchers observed MSA was best-suited to fiber spinning and roll-to-roll film production, while pToS is suited to 3D printing applications due to its 40 degree celsius melting point allowing nanotube solutions to be processed at a moderate temperature then solidified by cooling.
然后，团队将稳定的液晶溶液用于3D打印碳纳米管气凝胶，以及在各种不同表面上的丝网印刷图案。他们发现，MSA和PTO在此过程中没有释放有害烟雾，之后很容易清理。该过程完成后也可以回收酸，从而降低环境影响，能源和加工成本。
“The acids we’re using are so much gentler that you can use them with common plastics,” added Headrick. “That opens the door to a lot of materials processing and printing techniques that are already in place in manufacturing facilities.
“It’s also really important for integrating carbon nanotubes into other devices, depositing them as one step in a device-manufacturing process.”
Fine-tuning the next steps
莱斯大学团队的研究得到了几个著名组织的支持，包括Air Force Office of Scientific Research, the USDepartment of Energy, theNASA太空技术研究所, and theRobert A. Welch Foundation.
The next step for the team is to fine-tune the solvent for various specific applications and to determine how factors like chirality, when an object is distinguishable from its mirror image, and size affect nanotube processing. The researchers also pressed the importance of achieving high-quality, clean large diameter tubes.
Further information on the study can be found in the paper titled:“Versatile acid solvents for pristine carbon nanotube assembly,”published in the Science Advances journal. The study was co-authored by R. Headrick, S. Williams, C. Owens, L. Taylor, O. Dewey, C. Ginestra, L. Liberman, A. Ya’akobi, Y. Talmon, B. Maruyama, G. McKinley, A. Hart, and M. Pasquali.
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Featured image shows在赖斯大学开发的溶剂时，在此显微镜图像中看到的意大利面条般的碳纳米管缠结将不再是一个问题。图片通过帕斯奎利研究小组/赖斯大学。
