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In this paper we report an acid-modulated strategy for novel peptide microarray production on biosensor interfaces. We initially selected a controlled pore glass (CPG) as a support for solid-phase peptide synthesis (SPPS) to implement a chemistry that can be performed at the interface of multiple field effect transistor (FET) sensors, eventually to generate label-free peptide microarrays for protein screening. Our chemistry uses a temporary protection of the N-terminal amino function of each amino acid building block with a tert-butyloxycarbonyl (Boc) group that can be removed after each SPPS cycle, in combination with semi-permanent protection of the side chains of trifunctional amino acid residues. Such a protection scheme with a well-proven record of application in conventional, batchwise SPPS has been fine-tuned for optimal performance on CPG and, from there, translated to SPR chips that allow layer-by-layer monitoring of amino acid coupling. Our results validate this acid-modulated synthesis as a feasible approach for producing peptides in high yields and purity on flat glass surfaces, such as those in bio-FETs.

Miniaturization of the sensor active areas to length scales of the order of the analyte has been sought as means to reduce device footprints, and to capitalize on the novel optical and electronic enhancements that arise at this scale. However, little is known on what to expect of the sensor behaviour if the sensor footprints are shrunk to the dimensions of the order of analyte themselves. Our results demonstrate the densities and kinetics of adsorption of analyte to significantly increase with decrease in the sensor footprints to dimensions of the order of few multiples of analyte dimensions. Such increase is found to be generic, irrespective of the nature of interactions that drive adsorption, exhibiting qualitative similarity for electrostatic adsorption of nanoparticles, chemisorption of primary oligonucleotides, or complementary base pairing with target nucleotides. The carryover of these benefits onto a macroscopic sensor however requires high density nanopatterns exhibiting significant fill factors withtout compromising inter-feature isolation. The impact of feature dimensions, pattern fill factors, analyte concentrations, presence of convective flow, or the density of receptors are investigated using quantitative and real-time measurements of the nanostructure-analyte interactions using nanopatterned QCM sensors. The results indicate significant opportunities for rational design of nanopatterned macroscopic sensors, as well as nanoscopic sensors with sensor active areas of the order of analyte dimensions, e.g., electromagnetic hot-spots, or nanowire sensors.

Nanoplasmonic sensors based on surface-enhanced spectroscopies carry profound promise toward ultrasensitive detection of biomolecular analytes within miniaturized measurement footprints. High sensitivity in these sensors is achieved by intense electromagnetic (EM) enhancements at hot spots and colocalization of analytes with such hot spots. However, EM hot spots exhibiting high EM enhancements often present confined areas that render them inaccessible to large analytes such as biomolecules. Addressing this requires rational engineering of a nanoplasmonic interface that factors in the analyte surface concentrations and how they are distributed with respect to the EM hot spots. Here we demonstrate combination of metal-enhanced fluorescence (MEF) with a quartz crystal microbalance (QCM) through fabrication of highly resolved plasmonic nanoarrays directly on the QCM sensor. QCM and MEF are simultaneously employed to monitor in situ, real-time binding of fluorescently labeled protein to receptor-functionalized plasmonic arrays. The correlation between the QCM and MEF responses is used to quantify surface density of protein that contributes to the MEF signal intensities and obtain analyte distribution with respect to the EM hot spots by geometric modeling. Results further reveal the MEF assays to be sensitive down to ∼2 zmol of protein within measurement footprints that are 8 orders of magnitude smaller than that of the QCM.

A novel and flexible top‐down/bottom‐up scheme to achieve (sub‐)micrometer scale patterning of nanostructures with complementary micro‐/nanoarchitectures is presented. Nanostencils (perforated free‐standing Si3N4 membranes) are employed to pattern silicon nanopillars derived from the use of self‐assembled copolymer micelles as dry etch masks.

Block copolymer inverse micelles from polystyrene-block-poly-2-vinylpyridine (PS-b-P2VP) deposited as monolayer films onto surfaces show responsive behavior and are reversibly switchable between two states of different topography and surface chemistry. The as-coated films are in the form of arrays of nanoscale bumps, which can be transformed into arrays of nanoscale holes by switching through exposure to methanol. The use of these micellar films to act as switchable etch masks for the structuring of the underlying material to form either pillars or holes depending on the switching state is demonstrated.

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.

The controlled tuning of the characteristic dimensions of two-dimensional arrays of block-copolymer reverse micelles deposited on silicon surfaces is demonstrated. The polymer used is polystyrene-block-poly(2-vinylpyridine) (91 500-b-105 000 g mol-1). Reverse micelles of this polymer with different aggregation numbers have been obtained from different solvents. The periodicity of the micellar array can be systematically varied by changing copolymer concentration, spin-coating speeds, and by using solvent mixtures. The profound influence of humidity on the micellar film structure and the tuning of the film topography through control of humidity are presented. Light scattering, at. force microscopy, SEM, transmission electron microscopy, and XPS were used for characterization. As possible applications, replication of micellar array topography with polydimethylsiloxane and post-loading of the micelles to form iron oxide nanoparticle arrays are presented.

The continuous tunability of iron oxide nanoparticle dimensions is demonstrated using the pH controlled loading of ferric nitrate from aqueous solution into polystyrene-block-polyacrylic acid reverse micelles deposited on a silicon substrate. Quasi-hexagonally ordered two-dimensional arrays of iron oxide nanoparticles with a systematic tunability of particle heights in the sub-10 nm regime and a constant periodicity are obtained and characterized with atomic force microscopy and x-ray photoelectron spectroscopy.

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 nanocrystals

Nanoscale dispensing is a novel technique to deposit material on the micrometric and submicrometric scale. The nanoscale dispenser consists of a silicon nitride at. force microscope probe having an aperture in the apex of the hollow tip. This probe allows the deposition of individual ultrasmall droplets on a substrate, with vols. down to a few attoliters. The local deposition of liq. on a submicrometric scale can be used to induce a local modification of surface properties. Nanoscale dispensing was used to deposit an array of glycerol droplets on a self-organized micellar monolayer made of polystyrene-poly-2-vinylpyridine block-copolymers. The micelles had a poly-2-vinylpyridine core with a polystyrene corona. The presence of the glycerol droplets induced a local transformation in morphol. and surface chem. of the micellar monolayer. The area of the micellar film undergoing this reconfiguration was tuned by varying the deposition parameters during the nanoscale dispensing.