Nanoscale patterning with block copolymers

The self-assembly processes of block copolymers offer interesting strategies to create patterns on nanometer length scales. The polymeric constituents, substrate surface properties, and experimental conditions all offer parameters that allow the control and optimization of pattern formation for specific applications. We review how such patterns can be obtained and discuss some potential applications using these patterns as (polymeric) nanostructures or templates, e.g. for nanoparticle assembly. The method offers interesting possibilities in combination with existing high-resolution lithography methods, and could become of particular interest in microtechnology and biosensing

Nanoplasmonic Arrays with High Spatial Resolutions, Quality, and Throughput for Quantitative Detection of Molecular Analytes

Recent developments in nanoplasmonic sensors promise highly sensitive detection of chemical and biomolecular analytes with quick response times, affordable costs, and miniaturized device footprints. These include plasmonic sensors that transduce analyte-dependent changes to localized refractive index, vibrational Raman signatures, or fluorescence intensities at the sensor interface. One of the key challenges, however, remains in producing such sensors reliably, at low cost, using manufacturing compatible techniques. In this chapter, we demonstrate an approach based on molecular self-assembly to deliver wafer-level fabrication of nanoplasmonic interfaces, with spatial resolutions down to a few nanometers, assuring high quality and low costs. The approach permits systematic variation to different geometric variables independent of each other, allowing the significant opportunity for the rational design of nanoplasmonic sensors. The ability to detect small molecules by SERS-based plasmonic sensing is compared across different types of metal nanostructures including arrays of nanoparticle clusters, nanopillars, and nanorod and nanodiscs of gold

Nanopatterned Self-Assembled Monolayers by Using Diblock Copolymer Micelles as Nanometer-Scale Adsorption and Etch Masks

Nanopatterned self-assembled monolayers (SAMs) are obtained from a simple, straight-forward procedure by using masks derived from monolayers of block copolymer micelles. The nanopatterned SAMs consist of regularly spaced circular hydrophilic areas with diams. of approx. 60 nm on a continuous hydrophopic background or vice versa. The surfaces are shown to be excellent tools for the prepn. of arrays of nanocrystal

Optical Sensors Based on Whispering Gallery Modes in Fluorescent Microbeads: Response to Specific Interactions

Whispering gallery modes (WGMs) in surface-fixated fluorescent polystyrene microbeads are studied in view of their capability of sensing the formation of biochemical adsorption layers on their outer surface with the well-established biotin-streptavidin specific binding as the model system. Three different methods for analysis of the observed shifts in the WGM wavelength positions are applied and used to quantify the adsorbed mass densities, which are then compared with the results of a comparative surface plasmon resonance (SPR) study

Rational design of a planar junctionless field-effect transistor for sensing biomolecular interactions

In the ElectroMed project, we are interested in screening certain peptide sequences for their ability to selectively interact with antibodies or MHC proteins. This poses a combinatorial challenge that requires a highly multiplexed setup of label-free immunosensors. Label-free FET-based immunosensors are good candidates due to their high multiplexing capability and fast response time. Nanowire-based FET sensors have shown high sensitivity but are unreliable for clinical applications due to drift and gate stability issues. To address this, a label-free immuno-FET architecture based on planar junctionless FET devices is proposed. This geometry can improve the signal-to-noise ratio due to its larger planar structure, which is less prone to defects that cause noise and is better suited to the functionalization of different receptor molecules

Self-assembly of tunable, responsive polymer nanostructures:tools for nanofabrication of functional interfaces

The thesis presents a tool-box based on two dimensional self-assembly of diblock copolymer micelles to achieve nanostructures on surface with control over dimensions, spacing, surface-coverage and surface placement. Polystyrene-block-poly(2-vinyl pyridine), polystyrene-block-polyacrylic acid and polystyrene-block-polyferrocenyldimethylsilane have been used for the study. The utility of the self-assembly approach has been demonstrated by deriving other functional nanostructures like inorganic nanoparticle arrays and nanoscale pillars and holes on hard and soft substrates. In this respect, nanoparticle arrays of iron oxide with systematically tunable dimensions in the sub-10nm regime, creating sub-50nm wide Si, Si3N4, SiO2 and Quartz pillars and holes with varying aspect ratios and PDMS pillars/holes are presented. Preliminary results applying the nanostructured surfaces for applications such as carbon nanotube growth, controlling human stem-cell adhesion and expression, controlling columnar growth of physical vapor deposited TiN pyramids, and super-hydrophobic surfaces has been presented and discussed. The many interesting directions for future work based on the thesis results are presented in the outlook and where appropriate

Impact of Tether Length and Flexibility on the Efficiency of Analyte Capture by Tethered Receptors

Structure and functionality of molecular layers play a crucial role in determining the outcome of analyte-receptor interactions on affinity biosensors. The control over the structure of these molecular layers gives an independent means to enhance the sensor performance. Here we study the impact of the length and flexibility of molecular tethers on analyte capture by tethered receptors on quartz crystal microbalance and surface plasmon resonance sensors. Our results show clear enhancement of analyte-receptor interactions when receptors are bound to the sensor via flexible, and longer tethers. The findings further reveal a qualitative similarity of the impact of tether length on widely different type of binding interactions, viz. gold nanoparticle binding to tethered amine layers, and neutravidin binding to tethered biotin layers. By independent determination of tether densities, our investigations decouple the impact of receptor densities, and the tether conformations, and confirm the role of tether length on adsorption densities and kinetics. The results agree with theoretical reports in literature that predict enhanced analyte capture by receptors anchored to surface via long, flexible tethers, owing to enhanced freedom of movement and thereby its ability to “seek” the analyte in solution. These findings highlight the significance of factoring in the structure of the molecular tether to enhance analyte capture by tethered receptors, and thereby the performance of affinity biosensors

Wafer‐level Fabrication of sub 10 nm Gap Hot Spots for Highly Sensitive and Quantification of Biomolecules by Surface Enhanced Raman and Fluorescence Spectroscopies

International audienc