Thursday, February 25, 2010

Caltech Scientists Show Precise, Tunable Separation Between Nanomaterials with DNA Linker Polynucleotides

U.S. Patent Application 20100048421, FIG. 7 shows atomic force microscopy images of nanoassembly arrays made of DNA linker polynucleotides created at the California Institute of Technology (Caltech).  All Panels A to F are images for linker polynucleotides, which are used for separating nanomaterials and building nanodevices.


In U.S. Patent Application 20100048421, Caltech scientists disclose how to separate and organize carbon nanotubes into electronic devices using bits of DNA linker polynucleotides.  Professor of  Chemistry, Materials Science, and Applied Physics, Director, Materials and Process Simulation Center  Professor William A Goddard, III,  with researchers Si-Ping Han, Hareem Maune, and Robert D. Barish developed methods and systems that allow for precise, tunable separation between nanomaterials such as carbon nanotubes.  

FIG. 1 show a schematic representation of a linker polynucleotide according to several embodiments. Segment A comprises a dispersal domain consisting of thymine nucleotides. Segment B comprises an association domain. The spacer is a polynucleotide duplex region in the embodiment shown. 


FIG. 2 shows a schematic representation of a nanoassembly.


FIG. 3 shows a schematic representation two-dimensional array of nanoassemblies formed with DNA and carbon nanotubes. FIG. 3 shows a schematic of an array of parallel single wall carbon nanotubes (30) kept at fixed separation by the linker polynucleotide (10). The linker polynucleotides are arranged randomly along the nanotube axis but act collectively to keep the nanotube aligned and separated. In the schematic illustration of FIG. 3, carbon nanotubes are prevented from coming closer than the distance defined by the spacers because the spacers resist compression and bending. In particular, in this illustration carbon nanotubes are kept from moving further away than the distance allowed by the spacer because the spacer resists stretching, and because the nanotubes are adhered to the single stranded polynucleotide segments. Further, in the arrangement exemplified by the schematic illustration of FIG. 3 the shorter "B" segments, association domains (13) can now stably associate with neighboring carbon nanotubes because many spacers are acting collectively to stabilize the entire structure

FIG. 4 shows a schematic representation of proposed applications of several embodiments. Panel A shows a schematic representation of an array of single wall carbon nanotubes on a substrate. The arrow indicates the direction of a large scale alignment force. 
Panel B shows a schematic representation of a silicon wafer. The dark area has surface properties that prevent sticking of linker polynucleotide modified carbon nanotubes. The white areas have surface properties compatible with sticking of the carbon nanotubes. Arrays of parallel carbon nanotubes can form on the white areas.


Panel C shows four pictures of a single walled carbon nanotube forests taken at four different scales. The upper left panel shows a carbon nanotube forest on a silicon wafer. The top right panel is an SET image of a vertically standing carbon nanotube forest. Scale bar is 0.5 mm. The bottom left panel and bottom right panel are SEM images showing the top and sides of the forest. Scale bars are 5 .mu.m.




Panel D is a schematic representation of a diagram of a carbon nanotube forest after it has been dispersed using linker polynucleotides in situ. The left panel is a three-dimensional view, and the right panel is a top down view of the forest. 

FIG. 9 shows atomic force microscopy images of nanoassembly arrays according to several embodiments. Panel A shows a 1 mciron times 1 micron image of nanotube arrays, while Panel B shows an enlargement of the image shown in FIG. 7A


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