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Bubble expansion of homogeneous epoxy suspensions of nanowires and carbon nanotubes to produce large area films

The invention describes a general and scalable, low temperature method involving bubble expansion of homogeneous epoxy suspensions of nanowires and carbon nanotubes to produce large area films. The nanowires and carbon nanotubes are well aligned in the films, and the density can be readily controlled by starting suspension concentrations. Moreover, the average nanowire separation can be systematically controlled by adjusting the loading percentage of nanowires in the bubble solution.

The nanomaterial-embedded bubble films can be conformally transferred to a variety of substrates such as single crystal wafers, large flexible plastic sheets, highly-curved surfaces and also suspended across open frames. The bubble process produces very uniform film thickness of each bubble. The simplicity, generality, and potential to extend to much larger area films offers substantial promise for applications of one-dimensional nanowires and carbon nanotubes. This technique could offer substantial savings over traditional high-vacuum approaches to deposition.

The generality of this approach has been further shown with carbon nanotubes. The resulting single-walled nanotubes and multiple-walled nanotube films are distinct from previously reported filtration films, buckypapers, or yarned sheets. Filtration usually produces multiple layers overlapped nanotubes, while the single-walled nanotube films obtained through the bubble expansion method consist of a single-layer of ordered nanotubes. For making device arrays, individual nanotubes with controlled separation and alignment are more desired. The substitution of different nanowires or nanotubes enabled by this approach can be very attractive for creating different functional nanosystems with functionalities such as light-emitting diode arrays and logic/memory arrays.

This approach can be applicable to other types of nanostructures (e.g. nanoparticles) to produce very large scale thin film embedded with well-ordered nanomaterials.

This approach is general to other polymer/solvent systems, not limiting to current Epoxy/THF. For example, it is possible to prepare BBFs by using water/ethanol polymers (such as polyethylene oxide (PEO), polyvinyl alcohol (PVOH) and etc.), or photolithography-compatible polymers (e.g. SU-8 series photopolymer), which could be important to develop nanodevices for biological research, life sciences, etc.

Intellectual Property Status: Patent(s) Pending

Applications

Since their discovery over a decade ago, carbon nanotubes have been the subject of intense study because of their unique electrical, thermal, and mechanical properties. They have been proposed as the basis of new sensors, nanoscale electrical circuits, molecular delivery systems, photonic sources, thermal conductors, mechanical fibers, chemical catalysts, and as critical components for a wide variety of other applications.

Central to many proposed electronic device-based applications of nanowires and carbon nanotubes is the development of methods that enable organization over large areas with controlled orientation and density. While progress has been made in studies of individual or small numbers of nanowire and nanotube devices prepared by directed assembly and centimetre scale assembly of nanowire field effect transistor arrays by the Langmuir-Blodgett technique, it is unclear if these can be scaled to large wafers and non-rigid substrates needed for many applications and/or efficient processing. It is still imperative to promote the large scale assembly of well-ordered nanostructures with controlled orientation and density into hierarchical functional systems.

This general and scalable, low temperature method involving bubble expansion of homogeneous epoxy suspensions of nanowires and carbon nanotubes can produce large area films.

Applications include:
• Manufacturing different types of nanosystems
• Nanowire field-effect transistor devices and multifunctional coatings
• Continuous films production

Additional Information

  • Publication

    "Large-area blown bubble films of aligned nanowires and carbon nanotubes", G. Yu, A. Cao and C.M. Lieber, Nature Nanotech. 2, 372-377 (2007).

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