Architectural Elements

Revolutionary advances beyond existing technology as well as the development of entirely new technologies will require individual nanomaterials to be assembled and organized into architectural elements that possess functionality based on structural design. How nanomaterials are assembled into architectural elements is a key issue for the development of applications and devices because the form and structure of nanomaterials define its function and thus its usefulness. In other words, one can control and explore new and improved functions by designing and developing new architectural elements. A good example would be a new form of nanotube material developed in our group called "SWNT solid," in which aligned SWNTs are densely packed while retaining the intrinsic properties of SWNTs, such as high surface area, flexibility and electrical conductivity. Importantly, the shape is engineerable by controlling the fabrication process, which is beneficial for applications spanning from 100% binder-free SWNT electrodes for capacitors to flexible heaters. We are currently extensively exploring rational designs of architectural elements of nanotubes that can serve as building blocks for economical, scalable, and realistic nanodevice systems.

Development of new nanoscale structures and materials with controlled morphology, size, and structure is one of the key factors for applications and devices since these will define and enable control over physical properties. Particular emphasis in this general area is given in our group to develop scalable synthetic approaches to control the length, purity, diameter, and wall numbers of the nanotubes, and to understand how fundamental properties such as electronic, thermal conductivities or mechanical properties depends on these structures. Our ultimate goal in this direction is to produce the best nanotubes for any application and/or device. One example of structural control is the ability to tune the wall number of nanotubes by using engineered catalysts. Here we succeeded in selective synthesis of double-walled carbon nanotubes through catalyst engineering, determining the optimum mean tube diameter for selective DWNT synthesis, and growing CNTs with this optimum mean diameter by precisely controlling the Fe catalyst film thickness. These double-walled carbon nanotubes are expected to serve as excellent electrodes for field-emission displays.