报告时间：2016年12月21日10:30
报告地点：科技创新大楼C501室

Andrew Koltonow

Abstract:
Exfoliated thin sheets of layered materials can readily reassemble to form a macroscopic film with lamellar nanostructure. Our work shows that these films contain massive arrays of parallel two-dimensional (2D) nanofluidic channels, which exhibit enhanced unipolar ionic conductivity with the counterions as the majority charge carriers. Conceptually, the lamellar films are an ionic analogue to extrinsically doped semiconductor wafers, suggesting they could be used as a platform for integrated nanofluidic devices. We use the 2D nanofluidics platform to demonstrate “kirigami nanofluidics”, where ionic transport through such 2D channels can be manipulated by tailor-cutting the shape of the film. We find that shapes with asymmetric source and drain exhibit rectifying ionic currents that can be attributed to the effect of concentration polarization zones developed in the two reservoirs. The rectification ratio can be determined simply by adjusting the device shape, and Kirigami-made ionic rectifiers and resistors can be conveniently integrated into simple circuits, such as AND and OR logic gates. These results demonstrate a promising new way to manipulate nanoscale ionic transport by patterning materials at the macroscopic length scale. We expect the 2D nanofluidics platform will be a powerful tool for nanofluidics researchers, because it enables inexpensive, high-throughput fabrication of custom nanofluidic devices.

Bio:
I am from Michigan, USA. I got my bachelor’s degree in materials science and polymer chemistry at the University of Michigan, where I briefly worked on silane and silsesquioxane polymers with Richard Laine. Afterwards I came to Northwestern University to study soft matter interactions in graphene oxide and other 2D materials, as a graduate student in the research group of Jiaxing Huang. Now I am nearing the end of my graduate studies. A main goal of my research is to design sustainable nanomaterials technologies based on controlled self-assembly of earth-abundant precursors.

Xuan Dou

Title:Self-dispersed Crumpled Graphene Balls in oil for Friction and Wear Reduction

Abstract:
Ultrafine particles are widely used as lubricant oil additives since they can infiltrate and separate tribological contacts, thereby reducing the friction and wear between surfaces. They are more thermally and mechanically stable compared to molecular additives under high friction, and the good dispersibility of ultrafine particles without molecular ligands is highly desirable. Based on our previous report, ultrafine particles with miniaturized crumpled structure should self-disperse in lubricant oil, just like how crumpled paper balls do not readily stick to each other. Meanwhile, they could reduce friction and wear like miniature ball bearing. Here we report the use of crumpled graphene balls as a high-performance additive that can significantly improve the lubrication properties of polyalphaolefin base oil. In friction test, crumpled graphene’s tribological performance excels that of other carbon additives including graphite, reduced graphene oxide, and carbon black. Notably, polyalphaolefin base oil with only 0.01–0.1 wt. % of crumpled graphene balls outperforms a fully formulated commercial lubricant in terms of friction and wear reduction.

Bio:
Xuan is currently a 5th year Ph.D. Candidate at Department of Materials Science & Engineering of Northwestern University. Before this, he got the master degree of Chemical Engineering at University of Florida and bachelor degree of Mechanical Engineering at University of Science and Technology of China. At Northwestern, he mainly focuses on the engineering application of nano-materials and nanotechnology. One of his representative work is to apply crumpled graphene balls as advanced lubricant additive to significantly improve the lubrication performance, which is published as the cover article of PNAS and highlighted by Fortune news and C&EN news.