Artificial DNA nanostructures 1,2 show promise for the organization of functional materials 3,4 to create nanoelectronic 5 or nano-optical devices. DNA origami, in which a long single strand of DNA is folded into a shape using shorter 'staple strands' 6 , can display 6-nm-resolution patterns of binding sites, in principle allowing complex arrangements of carbon nanotubes, silicon nanowires, or quantum dots. However, DNA origami are synthesized in solution and uncontrolled deposition results in random arrangements; this makes it difficult to measure the properties of attached nanodevices or to integrate them with conventionally fabricated microcircuitry. Here we describe the use of electron-beam lithography and dry oxidative etching to create DNA origami-shaped binding sites on technologically useful materials, such as SiO 2 and diamond-like carbon. In buffer with 100 mM MgCl 2 , DNA origami bind with high selectivity and good orientation: 70-95% of sites have individual origami aligned with an angular dispersion (+ + + + +1 s.d.) as low as + + + + +108 8 8 8 8 (on diamond-like carbon) or + + + + +208 8 8 8 8 (on SiO 2 ).The semiconductor industry is currently faced with the challenges of developing lithographic technology for feature sizes below 22 nm (ref. 7) and exploring new classes of transistors that use carbon nanotubes 8 or silicon nanowires 9 . A major goal of nanotechnology is therefore to couple the self-assembly of molecular nanostructures with conventional microfabrication. A marriage of these so-called bottom-up and top-down fabrication methods would enable us to register individual molecular nanostructures, to electronically address them, and to integrate them into functional devices. One strategy is to use lithography to make templates onto which discrete components can self-assemble. Examples include the assembly of nanoparticles 10,11 , carbon nanotubes 12,13 and nanowires 14 . Lithographic templates can also be used to create hierarchical order: the nanostructures they organize can themselves have internal features with dimensions significantly smaller than those of the original template 15 and can serve as scaffolds for the assembly of still smaller components.Artificial DNA nanostructures are well suited to this approach. They can be synthesized with attachment groups (such as biotin or single-stranded DNA hooks) at defined locations, which can bind objects such as gold nanoparticles 4,16 . Easily designed in arbitrary shapes, DNA origami typically carry 200 such independently addressable sites at a resolution of 6 nm. Figure 1a depicts the self-assembly of triangular DNA origami in solution (see Supplementary Methods 1) and shows an atomic force micrograph (AFM) of their random deposition on mica, a technique ill-suited for integration with microfabrication. Previous lithographically patterned deposition of organic compounds 17 , single-and doublestranded DNA molecules [18][19][20] or DNA nanostructures 21 has achieved highly selective adsorption, but the molecules were smaller than the lith...

The ability to control the interaction of polyelectrolytes, such as DNA or proteins, with charged surfaces is of pivotal importance for a multitude of biotechnological applications. Previously, we measured the desorption forces of single polymers on charged surfaces using an atomic force microscope. Here, we show that the adhesion of DNA on gold electrodes modified with self-assembled monolayers can be biased by the composition of the monolayer and externally controlled by means of the electrode potential. Positive potentials induced DNA adsorption onto OH-terminated electrodes with adhesion forces up to 25 pN (at +0.5 V versus Ag/AgCl), whereas negative potentials suppressed DNA adsorption. The measured contributions of the DNA backbone phosphate charges and the doubly charged terminal phosphate on adsorption agreed with a model based on the Gouy-Chapman theory. Experiments on an NH(2)-terminated electrode revealed a similar force modulation range of the coulomb component of the desorption force. These findings are important for the development of new DNA-based biochips or supramolecular structures.

Cover: This cover illustrates the chemical structure of a highly branched polyurethane obtained using oligomeric poly(ethylene oxide) units in combination with an A2 plus B3 synthetic methodology. Size exclusion chromatography confirms the gradual increase in molar mass without the formation of crosslinked product. The molar mass between branch points permits the formation of more ductile films with facile melt processibility, and maintained ionic conductivity upon salt doping. Further details can be found in the

Soluble model segmented poly(urethane urea)s (PUU) with or without hard segment (HS) branching were utilized to explore the importance of hydrogen bonding and chain architecture in mediating the long-range connectivity of the HS phase. The HS content of all the PUU copolymers was 22 wt %, and the soft segment (MW 970 g/mol) was a heterofed random copolymer of 50:50 ethylene oxide:propylene oxide, which possesses a single terminal hydroxyl group (monol). An 80:20 isomeric mixture of 2,4-and 2,6-toluene diisocyanate, 4,4′,4′′-triphenylmethane triisocyanate and water were utilized during the chain extension step of the synthesis to incorporate HS branching. DSC and SAXS results on the final plaques indicated that the samples were still able to establish a microphase morphology even in the presence of the highest extent of HS branching utilized in the study. The tapping-mode AFM phase image of the PUU sample without HS branching exhibited the presence of long ribbonlike hard domains that percolated through the soft matrix. The long-range connectivity of the HS was increasingly disrupted with higher levels of HS branching. Accompanying such disruption was a systematic mechanical softening of the PUU samples. FT-IR indicated that incorporation of HS branching disrupted the hydrogen-bonded network within the hard phase. These results demonstrate the importance of hydrogen bonding and chain architecture in mediating the long-range connectivity and percolation of the HS and achieving dimensional stability.

Polyurethane Networks (PUNs) were synthesized using polyols derived from soybean oil, petroleum, or a blend of the two in conjunction with diisocyanate. The soybean-based polyols (SBPs) were prepared using air oxidation, or by hydroxylating epoxidized soybean oil. Some of the networks were subjected to several solvents to determine their respective swelling behavior and solubility parameters. Sol-fractions were also determined, and DMA experiments were utilized to monitor the changes in storage modulus and tan ␦ with temperature for networks with sol and with the sol extracted. A linear relationship was noted between the hydroxyl number of a SBP and the glass transition temperature of its corresponding unextracted PU network within the range of hydroxyl numbers (i.e., 55-237 mg KOH/g) and glass transition temperatures (i.e., Ϫ21-ϩ83°C) encountered in this work. This same linear relationship was realized between the weighted hydroxyl number of soy and petroleum-based polyol blends and the glass transition temperature of the resulting unextracted and extracted network PUs within the ranges utilized in this study (i.e., 44 -57 mg KOH/g, Ϫ54 -19°C).

Summary: Branched poly(arylene ether)s were prepared in an oligomeric A2 + B3 polymerization of phenol endcapped telechelic poly(arylene ether sulfone) oligomers as A2 and TFPPO as trifunctional monomer B3. The molar mass of the A2 oligomer significantly influenced the onset of gelation and the DB. A high level of cyclization during polymerization of low molar mass A2 oligomers (U3 = 660 and U6 = 1 200 g · mol−1) led to a high conversion of functional groups in the absence of gelation, and the level of cyclization reactions in the polymerization decreased as the molar mass of the A2 oligomer was increased. The pronounced steric effect in the polymerization of higher molar mass A2 oligomers (U8 = 1 800 and U16 = 3 400 g · mol−1) resulted in low reactivity of the third aryl fluoride in the B3 monomer. As a result, only slightly branched (U8 = 1 800 g · mol−1) or nearly linear (U16 = 3 400 g · mol−1) high molar mass products were obtained with higher molar mass A2 oligomers. The branched polymers exhibited lower Mark‐Houwink exponents and [η] relative to linear analogs, and differences between the branched polymers and linear analogs were less significant as the molar mass of the A2 oligomers was increased due to a decrease in the overall DB. magnified image

The development of single-molecule techniques has afforded many new methods for the observation and assembly of supramolecular structures and biomolecular networks. We previously reported a method, known as the single-molecule cut-and-paste approach, to pick up and deposit individual DNA strands on a surface. This, however, required pre-functionalization of the surface with DNA strands complementary to those that were to be picked up and then deposited. Here we show that single molecules of double-stranded DNA, bound to the tip of an atomic force microscope, can be deposited on a bare gold electrode using an electrical trigger (surface potential cycling). The interactions between the DNA and the electrode were investigated and we found that double-stranded DNA chemisorbs to the gold electrode exclusively at its end through primary amine groups. We corroborated this finding in experiments in which only a single adenosine nucleotide on a polyethylene glycol spacer was 'electrosorbed' to the gold electrode.

Summary: The oligomeric A2 plus monomeric B3 synthetic methodology provided highly branched, poly(ether urethane)s based on TMP (B3) and isocyanate endcapped polyethers. 13C NMR spectroscopic assignments for the branched polyurethanes were verified using model urethane‐containing compounds based on TMP and a monofunctional isocyanate (either cyclohexyl or phenyl isocyanate (PI)). Derivatization of hydroxyl endgroups with trifluoroacetic anhydride enhanced the 13C NMR resolution in spectra for branched polyurethanes. The 13C NMR resonance for the linear unit exhibited a broad shoulder due to quaternary carbons that were attributed to cyclic species in the highly branched polyurethanes. The classical DB calculation revealed the efficiency of the B3 monomer for branching; however, an equation that incorporated the linear contribution of the A2 oligomer provided a more accurate DB for highly branched polyurethanes.SEC chromatograms for increasing addition of A2.magnified imageSEC chromatograms for increasing addition of A2.