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NIRT: Hierarchical Bionanomanufacturing PI: Robert L. Clark 1. Co-PIs: Ashutosh Chilkoti 2, Eric Toone 3, and Stefan Zauscher 1 Mechanical Engineering and Materials Science1, Biomedical Engineering2, Chemistry 3, Duke University Abstract II) Localized Actuation of Thermally Responsive III) Fabrication of Bioconjugated and Hybrid Here we report on progress on our NIRT on hierarchical nanomanufacturing. I) First we Polymers and Polypeptides Polymeric Nanostructures by Field-Induced report on a holographic technique we adopted that provides a noninvasive laser-based approach for adaptable, real-time nanofabrication and nanomodification of (bio)- Scanning Probe Lithography polymeric materials substrates. II) We then discuss a technique we are developing in We are currently developing a novel and highly sensitive method of which optically addressable metal nanoparticles display large spectral shifts as a function sensing nanometer-scale distances between single nanoparticles (NPs) Highly controlled patterning of polymeric and biomolecular nanostructures on surfaces is a of subtle changes in distance from conductive films, and hence, represent a promising and conductive surfaces. Once characterized, this method will be used critical step in the fabrication of biomolecular devices and sensors. We use field-induced way to measure angstrom-scale distances in potential biosensor applications. III) Finally to indicate thermally responsive polymer actuation that is localized to scanning probe lithography (FISPL) to chemically modify polymer brushes to allow conjugation of we report on a process we developed for the chemical modification of protein resistant Au specific regions in-between metal nanoparticles and a conductive biomolecules. Surface-confined, non-fouling (i.e., protein resistant) poly(oligo(ethylene glycol) polymer brushes for the fabrication of protein arrays by field-induced scanning probe film. Here, the high-energy focusing capabilities of nanoparticles in methyl methacrylate) (p(OEGMA)) brushes were prepared on silicon substrates by surface- lithography. proximity to metal films upon laser irradiation will cause a temperature initiated atom transfer radical polymerization (SI-ATRP) in a “grafting-from” approach. These Au-coated glass increase, and likely trigger polymer actuation, in a highly localized p(OEGMA) brushes were then patterned directly on the nanoscale by FISPL, generating manner. chemical functionalities that allowed for subsequent protein conjugation (Schematic and AFM images below). Although our approach works, we do not yet have a complete physical-chemical I) Three-dimensional Dynamic Mask-Less understanding of the process. We hypothesize that -CH3 groups are oxidized in the presence of high electric fields and converted to -COOH groups. After chemical modification, protein Holographic Lithography conjugation is achieved on the patterned areas via biotin-streptavidin coupling. With this Spectroscopy of Nanoparticles near Gold Films approach we were able to create periodic BSA protein arrays with a feature width of ~130 nm. A method is presented for dynamic, computer-controlled, maskless beam-steering, by spatial light Single NP, TIR Illumination Non-specific adsorption of protein was dramatically reduced due to the non-fouling nature of the SPP and LSP Deconvolution polymer. modulators (SLMs), to address specific locations on arrays with large spatial and temporal (SPP + LSP) selectivity. The dynamic maskless holographic lithography (DMHL) approach is ideally suited to trigger and direct nanofabrication in the optical near-field through easily controllable far-field, DF Illumination And broad beam illumination sources. The beam from the laser is centered on the computer-controlled SPR Collection SLM, reflected into the microscope and directed upwards through the objective to illuminate the specimen plane. The optical system ensures the plane of the SLM is imaged to and completely fills the rear aperture of the microscope objective. Beam propagation from the rear aperture through the objective results in reconstruction of the original image on the micro/nanoscale. Au-coated glass slide Right prism SPR TIR Image/Specimen 26 nm 22 nm 18 nm 14 nm 10 nm 6 nm 2 nm 0 nm measurement Illumination Plane 60-nm Au NP SLM glass slide 45-nm Au film We also found that both (a) raised features and (b) trenches can be created on the p(OEGMA) Fourier Lens polyelectrolyte layer brushes by controlling the contact force between the tip and the substrate. While the feature size of the patterns could be controlled by adjusting the patterning parameters such as applied Layer-by-layer (LBL) assembly of oppositely charged polyelectrolytes (PELs) was used to control the distance voltage, relative humidity and tip velocity. We note that if a negative tip bias or no bias is applied between NPs and gold films. The surface plasmon polariton (SPP) resonance propagating along the gold film red with respect to the substrate, no appreciable changes are observed. This highlights the shifts as the number of PEL layers increases (left plot, green trend). Single NP spectra can be acquired using two directionality of the electrochemical process and shows that physical interactions between the tip different methods of illumination: i) dark field (DF) or ii) total internal reflectance (TIR) illumination. Dark field and the sample alone cannot be responsible for the formation of the patterns. illumination primarily excites the localized surface plasmon (LSP) resonance of the NP. Single NP spectra, obtained using DF illumination, are increasingly blue-shifted as the NPs are spaced further away from the high-dielectric gold film (left plot, blue trend). While TIR illumination primarily excites the SPP resonance of the gold film, LSP resonances of NPs in close proximity to the film are also excited via an evanescent field. For this reason, single NP a) b) spectra, obtained using TIR illumination, show a convoluted dependence on layer height that is dominated by the blue-shifting LSP when NPs are less than 14 nm away from the gold film, and by red-shifting (SPP-dominated) when NPs are further than 14 nm from the gold film (right plot). These data suggest that the SPR of NPs is shifted by ~12 nm for every 1-nm change in distance from 0 – 6 nm and ~7 nm for every 1-nm change in distance from 6 – 14 nm. With a high resolution grating this experimental design is potentially capable of sensing distance changes on the order of Ångstroms! Image Phase Hologram Reconstructed Image Localized Optothermal ELP Actuation We have made use of the chemical changes on the brush surface that occur due to the oxidative nature of the electrochemical patterning process and demonstrate that they can be used to Micro/Nano Patterning with 100x 1.25 NA create bioconjugated nanostructures. Our unique patterning approach can potentially form the basis for the fabrication of a large range of novel polymeric and biomolecular nanostructures that Photopolymer oil immersion objective may find application as biosensors or substrates for the precise presentation of biomolecular queues to cells. We are currently developing the tools and procedures to expand the lithographic cover glass Initial system testing was performed using approach into a massively parallel, anodization stamping process. a) b) an optically responsive epoxy (Norland H2O Photopolymer 63). (a) CAD-generated ELP pattern (b) SEM image taken normal to the Au-coated glass slide substrate surface showing 880 nm to 2.5 m feature widths. Note the letter „L‟ has fallen over due to post-processing after Acknowledgments patterning. (c) SEM images taken at a 40˚ dove prism We acknowledge support through NSF-NIRT 0609265. We also acknowledge the substantial and (d) 60˚ from the surface show the height of the features ranging between 3-5 contributions to the optothermal NP interrogation by Prof. David Smith and Jack Mock at Duke c) d) University. microns. With an optimized system and Preliminary experiments are aimed at localized actuation of elastin-like polypeptides (ELP, is a thermally responsive improved feedback control, resolution could polypeptide) sandwiched between single NPs and a gold film, using laser heating. The schematic experimental setup be improved to at least the diffraction limit of is shown above; the plot (above right) shows a shift of ~30 nm in the SPR response of a single nanoparticle after 1 ~ 250 nm. min of laser exposure. Although a spectral shift of this magnitude would indicate a change in distance between the NP and the gold film, it cannot yet be concluded that this shift is due to thermally induced changes in ELP conformation. Current studies are focused on characterizing spectral properties of NPs in close proximity to gold films with water as the surrounding medium to provide a distance calibration for localized ELP actuation experiments.
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