DNA-BASED MOLECULAR ELECTRONICS: International Symposium on DNA-Based Molecular Electronics
725(2004); http://dx.doi.org/10.1063/1.1805372View Description Hide Description
DNA molecule is a candidate electrical material for molecular devices. However, in order to realize a DNA molecular device, it is necessary to combine characteristics of DNA with semiconductor technology. DNA molecule is adsorbed not on the SiH surface but on the SiO2 surface by adding MgCl2 to DNA solution. In addition, DNA molecule can be selectively adsorbed to SiO2 surface in SiO2/SiH pattern, which is fabricated using photolithography, and DNA patterning is made on Si substrate. Since DNA molecule can be adsorbed to Si substrate through Mg 2+, the adsorption of DNA molecule in SiO2/SiH pattern is depended on the concentration of MgCl2 and the difference of chemical property between SiO2 surface and SiH surface. The optimum concentration of MgCl2 in which DNA is selectively adsorbed to SiO2 surface was 0.1 mM.
Multi‐Level Self Organization Process For A Parallel Fabrication Of Aligned Metal Structures In Microelectrode Gaps Using DNA And Metal Nanoparticles725(2004); http://dx.doi.org/10.1063/1.1805373View Description Hide Description
A fabrication scheme for the generation of metal nanostructures integrated in microelectrode gap arrays has been developed. The scheme uses self‐organization of molecular units such as long DNA and metal nanoparticles based on specific interactions. Thereby, it is open for parallelization as a typical requirement for future application of this approach. The assembly process is explained and demonstrated, and the results of ultramicroscopic characterization is presented.
725(2004); http://dx.doi.org/10.1063/1.1805374View Description Hide Description
Single wall carbon nanotubes (SWNTs) occupy a special place within molecular electronics. Indeed, they exist as semiconducting or metallic wires and have been used to demonstrate molecular devices like transistors, diodes or SET (single electron transistor). However, the future of this class of SWNT‐based devices is strictly related to the development of a bottom‐up self‐assembly technique. The exceptional recognition properties of DNA molecule make it an ideal candidate for this task. Here, we describe a non‐covalent method to connect carbon nanotubes to DNA strands using the streptavidin/biotin complex. Control experiments show that in absence of biotin, the DNA strand do not bind to SWNT. The binding of SWNT to DNA strand has also been carefully checked by washing experiments, showing the strength of the DNA anchorage on SWNTs. Combining this approach with molecular combing enable us to align nanotubes on substrate.
725(2004); http://dx.doi.org/10.1063/1.1805375View Description Hide Description
We are conducting experiments to fabricate nanotube‐based field effect transistors (FETs) using the molecular recognition properties of DNA. For this purpose, we have prepared single‐walled carbon nanotubes derivatized with PNA (peptide nucleic acid, a DNA analog) and have studied their attachment to free, complementary DNA. We are currently examining the prospects for assembling devices by hybridization of the PNA‐labeled nanotubes to DNA‐functionalized electrodes.
725(2004); http://dx.doi.org/10.1063/1.1805376View Description Hide Description
We have produced micromachined silicon substrates that provide unique spatial addressing for surface‐aligned DNA molecules. Repeated characterization of the same molecule using atomic force microscopy and/or scanning electron microscopy before and after nanofabrication treatments has been achieved. Utilizing these micromachined platforms as substrates in nanofabrication experiments enables the use of complementary microscopy techniques for data collection on selected features of interest at different stages of a nanofabrication process. In this way, a clear correlation of the information generated can be achieved.
725(2004); http://dx.doi.org/10.1063/1.1805377View Description Hide Description
In recent years, a number of research groups have begun developing nanofabrication methods based on DNA self‐assembly. Here we review our recent experimental progress to utilize novel DNA nanostructures for self‐assembly as well as for templates in the fabrication of functional nano‐patterned materials. We have prototyped a new DNA nanostructure known as a cross structure. This nanostructure has a 4‐fold symmetry which promotes its self‐assembly into tetragonal 2D lattices. We have utilized the tetragonal 2D lattices as templates for highly conductive metallic nanowires and periodic 2D protein nano‐arrays. We have constructed and characterized a DNA nanotube, a new self‐assembling superstructure composed of DNA tiles. We have also demonstrated an aperiodic DNA lattice composed of DNA tiles assembled around a long scaffold strand; the system translates information encoded in the scaffold strand into a specific and reprogrammable barcode pattern. We have achieved metallic nanoparticle linear arrays templated on self‐assembled 1D DNA arrays. We have designed and demonstrated a 2‐state DNA lattice, which displays expand/contract motion switched by DNA nanoactuators. We have also achieved an autonomous DNA motor executing unidirectional motion along a linear DNA track.
725(2004); http://dx.doi.org/10.1063/1.1805378View Description Hide Description
G‐wires are DNA superstructures based on quartet formation by four guanine (G) bases. These molecular structures reach the micrometer size scale by assembling short oligonucleotides of a guanine rich sequence. Physico‐chemical parameters were optimized to achieve optimal superstructure assembly. The combination of these superstructures with metal nanoparticles could provide new tools for a molecular nanotechnology. An assembly strategy has been developed and first experiments towards an inclusion of nanoparticles in the supramolecular assembly were conducted.
725(2004); http://dx.doi.org/10.1063/1.1805379View Description Hide Description
Hydration Layer Scanning Tunneling Microscopy (HLSTM) of quadruplex (“G‐wire”) DNA on mica was carried out under controlled humidity conditions. The G‐wires showed remarkable similarity with atomic force microscope images of the same DNA in air, i.e. increased lateral width due to tip broadening but with diameters similar to those measured by x‐ray techniques. The G‐wire height above the mica substrate and width appeared to decrease slightly with increasing humidity. Though much of the lateral broadening is likely a result of residual buffer salts and the lower resolving ability of HLSTM, the dependence of the DNA height and width on humidity suggests a simple explanation in terms of the hydration layer. An estimate of the increased thickness of the hydration layer of up to 0.6 nm was observed.
725(2004); http://dx.doi.org/10.1063/1.1805380View Description Hide Description
The high‐specificity self‐assembling nature of DNA makes the molecule a candidate for the template for the construction of molecular devices. In order to construct a functional device, the template must be positioned onto a predetermined site on a substrate to allow external connections, and the components must be properly aligned onto the template. A key factor is the high yield of binding, especially when the device consists of many components. Such high yield requires that the bases of the template DNA be exposed so that its counterpart can interact freely, and the template be stretched to avoid folding or coiling that hampers the interaction. We have developed electrokinetic DNA manipulation method, by which a double‐stranded DNA is stretched and immobilized bridging over an electrode pair, with the molecular ends anchored while the middle part is left free to interact with foreign molecules. However, double‐stranded DNA has a closed structure and the bases inside are not easily accessible. To have a template DNA with accessible bases, two methods are developed in this paper; one being the direct stretching of single‐stranded DNA, and the other being the use of a recombination protein to make the bases of double‐stranded DNA accessible. The former has an advantage in its simplicity, and the latter in its mechanical stability. We expect that these stretch‐and‐positioned DNA with accessible base‐pairs will lead to the high‐yield molecular construction.
725(2004); http://dx.doi.org/10.1063/1.1805381View Description Hide Description
Double stranded M13 phagemid DNA has been locally concentrated between interdigitated electrodes by dielectrophoresis. RF electric fields at 0.1 MHz and 1 MHz have been applied with field strengths exceeding 1 MV/m. Impedance changes were monitored by analysis of the driving signals or with an additional sensing signal applied at 1 kHz. DNA collection was found to be reflected clearly by changes in the capacitive part of the setup’s impedance. This presents a new method for a label free, purely electronic detection of macromolecules.
725(2004); http://dx.doi.org/10.1063/1.1805382View Description Hide Description
The integration of molecular structures into microscopic electrode arrays can be achieved by dielectrophoresis of gold nanoparticles in electrode gaps. Using microelectrodes realized by photolithography, we demonstrate here the generation of pearl chain arrangements of nanoparticles in structures accessible for standard technologies. In order to preserve the individual particle structures in the final nanowire arrangement, various strategies were employed. This method for defined positioning of nanoparticle chains offers the potential to wire DNA or DNA superstructures after conjugation to the particles and dielectrophoresis. It allows a parallel processing of molecular structures and their integration into microsystem technology.