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The authors’ recent concept of bioinorganic filtration devices made up of solid-state membranes (SSMs) accommodating ring-shaped, ribonucleic acid (RNA)-stabilized tobacco mosaic virus (TMV) coat protein (CP) assemblies with central 4 nm holes as genetically encoded ‘pore-in-pore’ fittings, to convey size and charge specificity to the membranes’ permeability, has been elaborated. Key developments for simplifying and finishing the unique combination apply to both soft- and hard-matter components: previous SSMs with millions of conical pores demanded sophisticated lithography to achieve a taper trapping the bionanopores upon insertion in a flow. Now focused helium (He) ion beam technology has enabled efficient, fast preparation of silicon nitride templates adapted to the nanorings. Proof-of-concept experiments reveal that negative charges imparted by nucleic acids exposed on the bionanopores might improve electrophoretic implantation further. Suitable peptides installed on the outer nanoring rim had been shown to nucleate spatially confined silica deposition from liquid precursors, which have been optimized in order to seal the annular gaps between bio and inorganic SSM pores by ‘bionic glue’. Finally, two engineered CP variants and a modified scaffold RNA were established for novel TMV nanoring types with altered pore charges, which also allow installing accessory molecules for advanced filtration and conversion tasks.

Measuring the mechanical properties of living tissue is a challenging task due to the small sizes and the fragility of the living organisms. A promising method, which works best on small scales, is the passive microrheology, which observes the motion of tracing beads within the sample. The video imaging method observes this motion by imaging the tracer particles with suitable optics (e.g. a microscope). As living tissue is a complex material, the viscoelastic properties are highly frequency dependent; therefore, a fast high-speed camera is needed to resolve the important frequencies in the 100 to 1000 Hz regime. As the data rate of high-speed cameras exceed the storage speed, only short burst of measurements can be carried out. This leads to a limited dynamic range of frequencies and missed measurement opportunities. It normally is not possible to track all the particles in real time to avoid the storage requirement of the video, as the tracking needs to be very precise and thus has a high computing demand. In this presentation, a combination of a CMOS imaging sensor with an FPGA is presented, which, in combination, allows for virtually unlimited long high-speed tracking of up to eight particles at up to 10 kHz. First, the sensor and the FPGA combinations are laid out. Secondly, the used particle tracking algorithm and its implementation is explained and benchmarked with a known state-of-the-art algorithm. Finally, this integrated sensor solution is mounted on a standard microscope and hour long tracking experiments on living 3T3 fibroblasts are carried out, studying the impact of blebbistatin on the mobility of polystyrene beads within the cell.

Nowadays, high-speed video microscopy is used in many applications like microrheology1, 2 or flow cytometry3 to measure mechanical properties of cells or to identify their type. Typically, high-speed cameras use buffering to reach very high frame rates due to the limited bandwidth of the interface to a PC like Ethernet or USB. Additionally, analysis of large data is compute-intense and in many cases difficult to do online. We developed a system that consists of a high speed CMOS image sensor combined with a field programmable gate array (FPGA) and a pulsed LED illumination system. Due to an image transformation that is done on the FPGA, the dimensionality of the data is reduced without loss of important information. This leads to a significant reduction of the amount of data as well as to noise reduction as a side effect. Furthermore, we developed a modular analysis toolkit that can be used to do the whole analysis directly on the same FPGA online so that buffering is not required and measurements can run continuously on high frame rates. Hence, we can analyze a large total number of objects at very high throughput rates in microfluidic devices. We present the analysis of diluted whole blood in a microfluidic system with our device as well as a sorting application that uses multiple regions of interest that are observed simultaneously so that particles can be analyzed before and after a manipulation or gate.

Active microrheology is a valuable tool to determine viscoelastic properties of polymer networks. Observing the response of the beads to the excitation of a reference leads to dynamic and morphological information of the material. In this work we present an expansion of the well-known active two-point microrheology. By measuring the response of multiple particles in a viscoelastic medium in response to the excitation of a reference particle, we are able to determine the force propagation in the polymer network. For this purpose a lock-in technique is established that allows for extraction of the periodical motion of embedded beads. To exert a sinusoidal motion onto the reference bead an optical tweezers setup in combination with a microscope is used to investigate the motion of the response beads. From the lock-in data the so called transfer tensor can be calculated, which is a direct measure for the ability of the network to transmit mechanical forces. We also take a closer look at the influence of noise on lock-in measurements and state some simple rules for improving the signal-to-noise ratio.

In the last decades, polymer brush coatings have proven to be excellent anti-fouling materials by preventing protein adhesion. When using this property to restrict cell growth laterally in cell culture, it is crucial to ensure that other cell functions remain unaffected. The present study therefore examines MC3T3-E1 cell growth and morphology on patterned PSBMA brush substrates and probes their proliferation potential at mRNA level. The osteoblastic cells display a more elongated morphology than cells on the control substrates, but show no sign of elevated levels of the apoptosis marker p53 or diminished levels of Ki-67 or H4, which serve as indicators of proliferation. Therefore, patterned polymer brushes do not seem to influence cells in their proliferation state and are suitable cell culture substrates. Nevertheless, the use of polymer brush surfaces in long-term cell culture was found to be limited by their instability in cell culture medium.

Two-dimensional gratings are generated on poly-carbonate films spin-coated onto thin gold–silver bimetallic layers by two-beam interference method. Sub-micrometer periodic polymer dots and stripes are produced illuminating the poly-carbonate surface by p- and s-polarized beams of a frequency quadrupled Nd:YAG laser, and crossed gratings are generated by rotating the substrates between two sequential treatments. It is shown by pulsed force mode atomic force microscopy that the mean value of the adhesion is enhanced on the dot-arrays and on the crossed gratings. The grating-coupling on the two-dimensional structures results in double peaks on the angle dependent resonance curves of the surface plasmons excited by frequency doubled Nd:YAG laser. The comparison of the resonance curves proves that a surface profile ensuring minimal undirected scattering is required to optimize the grating-coupling, in addition to the minimal modulation amplitude, and to the optimal azimuthal orientation. The secondary minima are the narrowest in presence of linear gratings on multi-layers having optimized composition, and on crossed structures consisting of appropriately oriented polymer stripes. The large coupling efficiency and adhesion result in high detection sensitivity on the crossed gratings. Bio-sensing is realized by monitoring the rotated-crossed grating-coupled surface plasmon resonance curves, and detecting the chemical heterogeneity by tapping-mode atomic force microscopy. The interaction of Amyloid-β peptide, a pathogenetic factor in Alzheimer disease, with therapeutical molecules is demonstrated.

Angular interrogation investigation of the rotated grating-coupled surface plasmon resonance was performed, via exciting plasmons on special sensing layers by a frequency doubled continuous Nd:Yag laser beam in Kretschmann arrangement. NBK7 glass substrates were evaporated by silver and gold layers having appropriate thicknesses to ensure a narrow plasmon resonance peak. Thin poly-carbonate films spin-coated onto the bimetallic layers were patterned by the fourth harmonic of a pulsed mode Nd:Yag laser applying a master grating-based interference method. The pulsed force mode atomic force microscopic investigation has shown the existence of a surface relief grating and a coexistent adhesion modulation having a period of 416 nm. The conditions of the grating-coupling effect were determined for shallow sub-micrometer polymer gratings, and secondary minima were detected on the resonance curves measured in presence of polymer patterns, according to the calculations. The indispensability of a minimal modulation amplitude and the existence of an optimal rotation angle of the grating grooves with respect to the plasmon propagation direction were experimentally proven. The position of the emerged secondary resonance minimum indicated that the average film thickness was decreased caused by material removal during the structure formation. It was shown by tapping-mode AFM that the sub-micrometer adhesion modulation resulted in periodic adherence of streptavidin in the structure’s valleys. The attachment of a small amount of protein was detected based on the shift of the secondary resonance peak. The capability of the polymer grating for sensitivity enhancement was demonstrated, proving that the secondary peak shift is highly sensitive to the protein concentration. The application of the polymer grating covered bimetallic films as transducing layers in novel bio-sensorization method based on rotated grating coupling is proposed.

Sub-micrometer periodic structures were prepared on the surface of poly-carbonate films by UV laser treatment methods: a) grating-like structures having a period of 156 nm were induced by ArF excimer laser, b) 416 nm and 833 nm periodic gratings were prepared by two-beam interference realized by the fourth harmonic of a Nd:Yag laser. The sub-micrometer adhesion pattern accompanying the topographical structure was determined by pulsed force mode atomic force microscopy. The difference between the measured adhesion modulation and the adhesion profile calculated based on the topography was explained by the UV laser illumination caused phase and chemical changes. XPS investigations proved that chemical modification of the polymer occurs and the degree of the photo-degradation depends on the treating laser wavelength as well as on the number and fluence of the laser pulses. It was demonstrated by tapping mode atomic force microscopy that bovine serum albumin attaches to surface parts having higher adhesion. The dependence of the protein adherence on the surface treatment conditions was demonstrated based on the C 1s and O 1s spectra and on the proteinaceous nitrogen level.

Two-beam interference method was applied to generate gratings having periods of 416 nm and 833 nm by the forth harmonic of a Nd:Yag laser on thin poly-carbonate films spin-coated onto silver layer-covered substrates. The dependence of the modulation depth on the fluence and number of laser pulses was investigated by atomic force microscopy. A secondary pattern appeared on very thin polymer layers thanks to the “p” polarized laser beam illumination induced self-organized processes. The conditions of the emergence of grating-coupling caused additional plasmon resonance peak were determined for the sub-micrometer periodic polymer gratings. Surface plasmon resonance measurements were performed in attenuated total reflection arrangement to determine the effect of the angle between the plasmon propagation direction and the polymer groves on the grating-coupling. The effect of the modulation depth on the grating-coupling caused additional resonance minimum was also analyzed. We found coupling phenomena according to our calculations, the differences between the measured and theoretically predicted resonance curves were explained by the scattering on the complex surface structure.

Grating-like structures having a period of 416 nm were produced on the surface of poly-carbonate films by two-beam interference realized by the fourth harmonic of Nd:Yag laser. The period of the structures was half of that the applied master grating, the ratio of the width of the valleys to the period was tuned by the intensity, the depth of the modulation was increased by the number of laser pulses. Pulsed force mode atomic force microscopy was applied to study the topography and the adhesion on structured surfaces with sub-micrometer resolution. The adhesion modulation caused by the topography was calculated along line cross-sections of the AFM pictures taking into account the tip and surface geometry. The separation of the effects of the topography and the laser-induced material changes proved that the adhesion is increased at the areas illuminated by laser beam having a fluence above the melting threshold. The laser-induced material changes cause an additional adhesion increase at the valleys of the structure. It was shown that the adherence of albumin results in dense packing on poly-carbonate surface parts having sub-micrometer periodic adhesion modulation.

Sub-micrometer periodic gratings were generated on thin poly-carbonate films spin-coated onto thin flat silver layer covered BK7 substrates by two-beam interference realized with the fourth harmonic of the Nd:Yag laser. The 416 nm period of the laser-induced grating was half of the applied master grating, the modulation depth was increased by the number of laser pulses at a given intensity. Attenuated total reflection measurements were performed in case of plasmon propagation directions parallel and perpendicular to the grooves, and on rotated gratings oriented at angles making the grating coupling effect detectable. Atomic force microscopy (AFM) was applied to determine the modulation depth of the gratings. It was shown that the periodically corrugated polymer surfaces resulted in the coupling of the surface plasmons already when the structure period was very close to the plasmon wavelength. The small shift of the resonance positions proved that the modulation depth cannot be explained by material removal, the material rearrangement plays an important role in the grating formation. These experimental results correlate with our temperature model calculations revealing that there is softening on the upper polymer surface and melting down to the silver layer at the lowest and highest applied laser fluences, respectively.

An atomic force microscopic method to study the incubation states of UV laser irradiated polymer samples is presented. Targets were illuminated by different number of pulses at 5.8 and 8.9mJ∕cm2 fluences. The induced adhesive and morphological changes were investigated simultaneously by an atomic force microscope equipped with a pulsed force mode extension. Importantly, below 100 pulses morphological changes were not observable while significant changes in the adhesion were found as a result of the incubation at 8.9mJ∕cm2 fluence. This method allows the imaging and detection of the whole laser modified area with nanometer resolution.

Teflon thin films were prepared via pulsed laser deposition using an ArF excimer laser (λ=193 nm, FWHM=20 ns) from pressed powder pellets. The applied fluence was 6.25±0.23 J/cm2, the number of pulses was 10 000, the pressure in the vacuum chamber was 2×10−5 Torr and the substrate temperature was 250 °C. The layers were post-annealed at temperature within the range 320–500 °C. The atomic force microscopy and pulsed force mode atomic force microscopy (PFM) investigations demonstrated that the effective surface reaches its maximum at 320 °C. At higher temperatures (360–500 °C) it decreased significantly to an approximately constant value. Measuring the local adhesion the difference between the adhesion forces at 320 and 360 °C was kept within the error range. Increasing the annealing temperatures, the adhesion force decreased over the investigated range. Post-annealing of the samples at 360 °C resulted in highly crystalline spherulites with lateral dimensions of several hundred micrometers. By optimizing the heating and cooling rate during the annealing the average dimension of spherulites increased and ringed structures were obtained. The PFM measurements showed that the adhesion force increased significantly compared to the similar samples without ringed structures.

Poly-carbonate films containing different types of original surface roughness were illuminated by a polarized ArF excimer laser beam having a fluence of 4 mJ/cm2. Atomic force microscopy was applied to study the laser-induced periodic surface structure formation process at 0°, 30° and 45° angles of incidence. The effect of initial surface structures on the intensity distribution was investigated in cases of: (a) grains on oriented and amorphous thick films; (b) holes on thin spin-coated films; and (c) nanoparticles arranged along micrometer long sides of hexagons below the spin-coated films. The presence of the scattering objects caused symmetry breaking, if the samples were illuminated by oblique incident ‘s’ polarized beam. The Fourier analysis of the AFM pictures has shown the competition of structures having different periods. The characteristic of the permanent surface patterns proved that the interference of the incoming beam and the beams scattered on previously existing structures is the LIPSS generating feedback process. Ring-shaped structures having 228 nm diameter were produced.

Sub-micrometer grating-like structures were generated on the surface of poly-carbonate (PC) films by polarized ArF excimer laser illumination well below the material ablation threshold. The period of the laser-induced surface structures was tuned by modifying the angle of incidence of the laser beam. The depth of the modulation was enlarged increasing the number of the laser pulses. The surface changes caused by the laser illumination were investigated by atomic force microscope operating in pulsed force mode. It was proven that not only the topography, but also the micromechanical properties are modulated with sub-micrometer period. Interestingly, the measured adhesion modulation is different from the adhesion modulation calculated by taking into account the tip and sample geometry. The co-existence of a reversed adhesion modulation was proven: the adhesion is increased at the hills caused by material changes, which may over-compensate the topographical effects. FTIR investigations have shown that chemical changes accompany the phase transitions leading to the structure formation.

Periodic structures were studied on spin-coated poly-carbonate (PC) films: (a) sub-micrometer laser induced periodic surface structures (LIPSS) were generated by polarized ArF excimer laser beam; (b) micrometer periodic lines were ablated by imaging a mask onto the samples. The change in the thickness and the surface roughness was determined by an attenuated total reflection setup. The difference between the resonance places measured on the structured and untreated surfaces was very small in the case (a), proving that there is no significant material removal during LIPSS formation. The plasmon scattering caused by the sub-micrometer roughness weakly depends on the direction of the plasmon propagation. The broadening of the resonance curve started after 400 laser pulses, the roughness increased up to 800 laser pulses and after 1000 pulses the curve became more narrow corresponding to the changes in the topography detected by atomic force microscopy. The shift of the resonance peak measured on the ablated samples (b) indicated a change in thickness corresponding to the rate of ablation. The effect of the micrometer structures on the broadening of resonance curves depends on the direction of plasmon propagation.

We present a method to measure contact angles of microscopic droplets with a conventional microscope that possesses a precision focus adjustment stage. The droplets are modeled as spherical caps that act as lenses. Their focal length is determined by measuring the distance from the substrate surface to the level where a sharp image of the aperture stop is observed. The lens diameter is found by edge detection of a microscope image of the microdroplets. The spherical cap model relates the focal length and diameter of such lenses to the contact angle of the used liquid with known refractive index. The measurement procedure was applied to condensed water droplets on a silicon substrate covered by its native oxide layer. The results are found to be in good agreement with conventional, goniometric sessile drop measurements of the advancing contact angle.

We present a method to detect adhesive forces of nano particles by analysis of the distribution of measured lateral forces. The measurement protocol is suitable for all types of atomic force microscopes with a lateral force channel. Lateral forces are measured, in constant normal force contact mode, by scanning of substrates decorated with nano beads. By using probability theory, geometry based measurement errors are compensated and the real adhesion force is determined within a given confidence interval. The theoretical model can be adapted for particles with arbitrary shape and distribution of adhesion forces. It is applied to the adhesion problem of spherical particles with a Gaussian distribution of adhesion forces. We analyze the measured force distribution qualitatively and quantitatively. The theory predicts a systematic underestimation of the mean value of any particle adhesion measurement done by lateral pushing. Real measurement data of 50 nm diameter silica nano beads on silicon substrate is used to test the theoretical model for plausibility by means of information theory.

A multicolor scanning near-field optical microscope (color-SNOM) has been developed to provide real color images of nanoscopic samples for biological and spectroscopical purposes. The sample illumination consists either of a single or a combined beam of different laser wavelengths. A common SNOM setup has been modified in a way that three photomultipliers for blue, green, and red light detection and color separating dichroic filters have been implemented. With this beam splitter device, it is possible to acquire simultaneously with the topography three color optical images on three different channels. In order to improve the signal-to-noise ratio, etched fiber tips with a high transmission intensity were used. Fluorescence experiments on latex beads labeled with two different dyes and transmission measurements on gold nanoparticles show a wavelength dependent optical contrast. The color-SNOM appears as a powerful tool for high resolution color spectroscopy.

Laser-induced periodic surface structures (LIPSS) were generated on oriented and amorphous thick, as well as on spin-coated thin, poly-carbonate films by polarized ArF excimer laser light. The influence of the film structure and thickness on the LIPSS formation was demonstrated. Below a critical thickness of the spin-coated films the line-shaped structures transformed into droplets. This droplet formation was explained by the laser-induced melting across the whole film thickness and subsequent de-wetting on the substrate. The thickness of the layer melted by laser illumination was computed by a heat-conduction model. Very good agreement with the critical thickness for spin-coated films was found. The original polymer film structure influences the index of refraction of the thin upper layer modified by the laser treatment, as was proven by the dependence of the structure’s period on the angle of incidence both for ‘s’- and ‘p’-polarized beams. The effect of the original surface roughness – grains in thick films or holes in thin films – was studied using atomic force microscopy. It was shown that the oblique incidence of ‘s’-polarized beams results in an intensity confinement in the direction of the forward scattering and in asymmetrical interference pattern formation around these irregularities. A new, two-dimensional grating-like structure was generated on spin-coated films. These gratings might be used as a special kind of mask.

A new two-step method to fabricate scanning near-field optical microscope (SNOM) probes with an aperture size clearly below 100 nm has been developed. For the first step, a chemical etching process is used in which an optical fiber is dipped with its acrylate jacket into hydrofluoric acid to get a suitable tapered shape of the fiber. The second step consists of beveling the etched fiber using a modified micropipette beveler to obtain a tip diameter in the nanometer range as well as a smooth surface to allow a good aluminum metallization by evaporation. By varying the beveling angle tapered shapes with different cone angles can be obtained. First transmission experiments with our probes show an optical resolution below 80 nm. In comparison to fiber tips obtained by a standard heating and pulling method, the transmission efficiency of these tips is up to three orders of magnitude higher due to the optimized tapered shape.

Scanning Force Microscopes excert lateral forces on the sample during measurement. The recording of the magnitude of these forces as a function of position gives friction maps. The possible scanning speeds of SFM, however, are far below the velocities of practical devices. The dynamic friction force measurement provides a solution to this problem. The sample is modulated laterally at frequencies up to several kilohertz and with amplitudes in the nanometer range. It is shown that the interaction with the sample is not only determined by friction, but also by the viscoelastic response of the sample. The combination of dynamic friction measurement with the intermittent contact measurement mode, the PulsedForceMode, gives full access to the relevant sample parameters: topography, lateral ‘friction’ forces, adhesion, sample stiffness and relaxations times.

Four amphiphilic peptides with designed hairpin structure were synthesized and their monolayers were employed as model systems to study biologically inspired calcium carbonate crystallization. Langmuir monolayers of hairpin peptides were investigated by surface pressure area isotherms, surface potential isotherms, Brewster angle microscopy (BAM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. A beta-hairpin conformation was found for all peptides at the air-water interface although their packing arrangements seem to be different. Crystallization of calcium carbonate under these peptide monolayers was investigated at different surface pressures and growth times both by in situ optical microscopy, BAM and ex situ investigations such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). An amorphous calcium carbonate precursor was found at the initial crystallization stage. The crystallization process occurred in three stages. It starts from the nucleation of amorphous particles being a kinetically controlled process. Crystal nuclei subsequently aggregate to large particles and vaterite crystals start to form inside the amorphous layer, with the monolayer fluidity exerting an important role. The third process includes the re-crystallization of vaterite to calcite, which is thermodynamically controlled by monolayer structural factors including the monolayer flexibility and packing arrangement of the polar headgroups. Thus, the kinetic factors, monolayer fluidity and flexibility as well as structure factors govern the crystal morphology and polymorph distribution simultaneously and synergistically.

We describe the pulsed-force mode, a new measuring mode for the scanning force microscope to image elastic, electrostatic and adhesive properties simultaneously with topography. The pulsed-force mode reduces lateral shear forces between the tip and the sample. Even very delicate samples can be mapped at high lateral resolution with full control over the force applied to the sample. The achieved scanning speed is comparable to that in contact-mode operation. The pulsed-force mode electronics can easily be added to many microscopes without much alteration of the original set-up. No change of the data acquisition software or of the feedback circuit is necessary.

We introduce an improved piezoelectric shear-force feedback system for tip-sample distance control in a scanning near-field optical microscope. A tapered glass fiber is glued into a metal tube and both are integrated in a mounting, sandwiched between two piezosegments. One of the piezoelements excites the fiber tip at mechanical resonance while the other one is used for detection. During surface approach the fiber resonance is damped by shear forces, which is registered by the second piezoelement and used for distance control. The main attractions of this setup are its simplicity, its compactness, and the lack of disturbing light sources. The fiber is easy accessible and tip exchange is simple. With an acceptable fiber amplitude of 5–10 nm (peak to peak) we obtained a topographical resolution of 5 pm/Hz. The geometry also allows the measurement of samples covered with a few millimeters of liquid, which is important for applications in biology and medicine.

We present an easy‐to‐use non‐optical shear‐force detection system for tip–sample distance control in scanning near‐field optical microscopes. The fibre tip is fixed in a four‐segmented piezo‐tube by a polymer, Polyisobutylene, which couples the tip stiffly to the piezo at frequencies of 10 kHz or more at room temperature. One segment of the piezo‐tube excites the fibre tip in resonance, while the other three segments detect the tip vibration in the manner of a piezo‐microphone. When the tip is damped by shear forces the induced voltage at the three segments changes and can easily be detected with a lock‐in amplifier. Further our method allows a fast and reproducible tip exchange with minor adjustments of mechanical or electrical components. We demonstrate the performance of our distance control on a holographically fabricated line pattern with 417 nm lattice spacing and 10 nm height. A height resolution of better than 1 nm is demonstrated.

We have used ion beam analysis and scanning near-field optical microscopy to characterize the three-dimensional domain structure of a thin film of a phase-separating polymer mixture. In the initially mixed film, there first occurs coverage of one of its surfaces by an unbroken layer of one phase; between this wet surface and the substrate, layers of domains form. Eventually, the layered domain structure becomes unstable, and a transformation occurs to the equilibrium wetting state where both phases are in contact with both surfaces, causing a phase separation to be purely two-dimensional at later times. During this transient wetting process, lateral and vertical domain sizes grow with time as t1/3 independent of the dimensionality of the domains.

Opaque samples are imaged by Scanning Nearfield Optical Microscopy (SNOM) in reflection mode: A quartz glass fiber tip is used both to illuminate the sample and to collect light locally reflected from or emitted by the surface. The collected light is coupled out by a 2×2 fiber coupler and fed into a grating spectrometer for spectral analysis at each sampled point. The tip-sample distance is controlled by a shear-force feedback system. The simultaneous measurement of topography and optical signals allows an assessment of imaging artifacts, notably topography-induced intensity changes. It is demonstrated that an optical reflectance contrast not induced by topographic interference can be found on suitable samples. Local spectral analysis is shown in images of a photoluminescent layer.

A novel method for high-speed fabrication of large scale periodic arrays of nanoparticles (diameters 40-200 nm) is developed. This method is based on a combination of nanosphere lithography and laser-induced transfer. Fabricated spherical nanoparticles are partially embedded into a polymer substrate. They are arranged into a hexagonal array and can be used for sensing applications. An optical sensor with the sensitivity of 365 nm/RIU and the figure of merit of 21.5 in the visible spectral range is demonstrated.

We demonstrate the adaption of a further developed Mach–Zehnder interference (MZI) microscope for the rapid 3D characterization of transparent microstructured polymer thin films. In order to quantify the accuracy of the Mach–Zehnder interferometer, comparative film thickness measurements of photolithographically patterned poly(methacrylic acid) polymer brushes are performed employing two alternative techniques: white light profilometry (WIM) and atomic force microscopy (AFM). When the refractive index of the polymer brushes is calculated from MZI data, we obtain a good agreement with results received from an independent method (ellipsometry). In contrast to surface probing techniques such as AFM or WIM, Mach–Zehnder interferometry is a transmitted light method that measures both surface height profiles and refractive index distributions. MZI thus enables the quantification of film homogeneity with respect to height and density variations at the lateral resolution of a refraction limited microscope. We conclude that MZI is an adequate tool for the rapid and non-destructive characterization of structured polymer thin films. This method should be particularly useful for production quality control of microstructured polymer thin films which possess great potential in electronic device fabrication and biotechnology.

To obtain a more fundamental understanding of macroscopic tribological processes, investigations on a microscopic or even atomic scale have to be undertaken. Macroscopic mechanical concepts of adhesion and friction phenomena are not adequate for explaining “nanomechanics”. The development of local probe techniques (scanning tunneling microscopy, atomic force microscopy) offered powerful new tools for studying microscopic, i.e. local, surface properties. One possible application of these instruments is local friction investigation by simulating a single asperity contact of a real surface with an atomic force microscope tip, and measuring normal and lateral forces occurring at the tip while imaging a sample. With respect to the enormous effect of environmental conditions on which local tribological interactions take place, rigorous control of the atmosphere is needed. We present details of an instrument suited for carrying out local friction investigations in controlled atmospheric conditions or on samples embeded in an extended experimental environment. The instrument's conception and possible applications are described, especially its combination with an electrochemical cell and potentiostatic control of a sample immersed in electrolytes. First results obtained with such a set-up are presented.

The authors show the simultaneous recording of normal and lateral forces arising in scanning force and friction microscopy on a potential controlled sample immersed in aqueous electrolyte. As a liquid film is present on virtually all solid surfaces under ambient conditions, it is important to control the properties of the solid/liquid interface. In order to obtain reliable information on the friction behaviour of such a surface, a set-up for potentiostatic control of the sample was established. Experiments have been carried out with a stand-alone scanning force and friction microscope (SFFM), combined with an electrochemical cell providing potential control of the sample. First results of simultaneous normal and friction force measurements, obtained on highly oriented pyrolytic graphite (HOPG) immersed in NaClO4, demonstrate the promising potential of the method.

The intensity of the evanescent electromagnetic wave of optically excited surface plasmons was measured directly using a scanning tunneling optical microscope (STOM) setup. When resonant coupling of the driving field to the surface plasmons was achieved, the measured intensity was increased by a factor of 30 larger than the corresponding evanescent wave intensity on a bare glass surface, in agreement with the theoretical prediction. Experimental results are presented for three laser wavelengths (514 nm, 633 nm, 670 nm). Possible applications of the technique to study surface plasmon fields are discussed.

Scanning probe microscopes can probe a variety of quantities characterizing surfaces. This overview paper describes techniques applicable in an ambient environment and having the power to distinguish different materials: the scanning force and friction microscope and the scanning nearfield optical microscope combined with a spectrometer. The basic operating principles of these two microscopes are described. Selected experiments point to possible future applications: we discuss scanning force and friction microscopy of ZnSe on GaAs and of Na, K-ATPase and near-field optical microscopy of a grating and of micropores.

Since the introduction of the STM in 1981 and the AFM in 1985, many variations of probe-based microscopies, referred to as SPMs, have been developed. While the pure imaging capabilities of SPM techniques initially dominated applications of these methods, the physics of probe–sample interactions and quantitative analyses of tribological, electronic, magnetic, biological, and chemical surfaces using SPMs have become of increasing interest in recent years. SPMs are often associated with nanoscale science and technology, since they allow investigation and manipulation of surfaces down to the atomic scale. As our understanding of the underlying interaction mechanisms has grown, SPMs have increasingly found application in many fields beyond basic research fields. In addition, various derivatives of all these methods have been developed for special applications, some of them intended for areas other than microscopy.

We present a new design for a compact stand-alone force and friction microscope. Both the force sensor and the scanning unit are mounted on the microscope head, thus allowing the investigation of virtually all surfaces, independent of thickness and size, and minimizing the geometrical dimension. The beam deflection method in a collinear arrangement is used to detect the normal force and the friction force. The cantilever is fixed to the scanning piezo. The influences of the scanning motion on the force signal and the compensation schemes are discussed. The new design of the SFM allows a combination of optical surface manipulation and real-time detection of the stimulated processes with the scanning force microscope. The set-up also makes it possible to work under fluids.

In an optical lever set-up one or two modulated laser beams of 0,1 to 6 mW modulation amplitude at a wavelength of 670 nm were focused at uncoated and gold-coated microfabricated cantilevers. The motion of the levers was analyzed by an optical lever set-up. The mechanical resonance (30 to 60 kHz) of the cantilevers was excited by the modulated light both in air and under vacuum conditions (10 6 mbar), The measured resonance frequencies and the width of the resonances were identical to the values found by exciting the cantilevers by piezo ceramics. At low frequencies under vacuum conditions, we found an increase of the oscillation amplitude with decreasing frequency. The time constant of this increase is of the order of 5 ms. At the resonance frequency of uncoated cantilevers light pressure effects dominate thermal effects; the resonance is thus excited by light pressure. Gold-coated cantilevers, however, are driven by the bimetal effect, even above 10 kHz. A possible application of the light pressure effects is the use of a modulated light beam in the attractive mode operation of a scanning force microscope to excite the cantilever oscillation.

Novel plasmonic sensor chips are prepared by generating sub-micrometer periodic patterns in the interfacial layers of bimetal-polymer films via master-grating based interference method. Poly-carbonate films spin-coated onto vacuum evaporated silver-gold bimetallic layers are irradiated by the two interfering UV beams of a Nd:YAG laser. It is proven by pulsed force mode AFM that periodic adhesion pattern corresponds to the surface relief gratings, consisting of sub-micrometer droplet arrays and continuous polymer stripes, induced by p- and s-polarized beams, respectively. The characteristic periods are the same, but more complex and larger amplitude adhesion modulation is detectable on the droplet arrays. The polar and azimuthal angle dependence of the resonance characteristic of plasmons is studied by combining the prism- and grating-coupling methods in a modified Kretschmann arrangement, illuminating the structured metal-polymer interface by a frequency doubled Nd:YAG laser through a semi-cylinder. It is proven that the grating-coupling results in double-peaked plasmon resonance curves on both of the droplet arrays and line gratings, when the grooves are rotated to an appropriate azimuthal angle, and the modulation amplitude of the structure is sufficiently large. Streptavidin seeding is performed to demonstrate that small amount of protein can be detected monitoring the shift of the secondary resonance minima. The available high concentration sensitivity is explained by the promotion of protein adherence in the structure's valleys due to the enhanced adhesion. The line-shaped polymer gratings resulting in narrow resonance peaks are utilized to demonstrate the effect of therapeutic molecules on Amyloid-B peptide, a pathogenic factor in Alzheimer disease.

In order to apply scanning near-field optical microscopy to life science, it is essential to have an accurate distance feedback that also works on soft biological samples in liquids. In this letter, we report measurements of neuron cells in aqueous solution using an advanced piezoelectrical shear-force detection setup. Simultaneously obtained topographical and fluorescence images are presented, demonstrating a resolution below 100 nm in the optical image. The influence of the water level on the shear-force signal and the interaction between near-field probe and soft organic samples are discussed. Stable feedback in fluids is obtained with tip–sample interaction forces below 100 pN.

In this study we investigated the contrast of lateral force at highly oriented pyrolytic graphite steps in an electrolytic environment with a scanning force and friction microscope. A characteristic enhancement of lateral force was visible. Steps were imaged with and without electrochemical potential control whereby a change of friction with potential could be observed. The behaviour of lateral force at the steps indicated that the observed contrast enhancement must be a real friction effect and is not caused solely by the topography.

Using a near-field scanning optical microscope (NSOM), crystals of zinc-porphyrin network materials are characterized with respect to morphology and fluorescence. Needle-shaped crystals are observed. While the topography is flat, the fluorescence intensity profile in the width direction is approximately triangular. A numerical calculation shows that differences between the topographic and optical images cannot be due to an artifact. In some needle-shaped crystals, the fluorescence emission is strongly peaked at one or both ends, possibly indicating a polar crystal structure.

Lateral integration of optoelectronic devices comprising strained multiple quantum well (MQW) structures can most successfully be accomplished by selective area epitaxy using metal organic molecular beam epitaxy (MOMBE). We optimized the growth parameters with respect to a planar butt coupling and sharp, flat MQW interfaces in an integrated MQW laser / MQW modulator structure. Defect generation in metal organic vapor phase epitaxy (MOVPE) overgrown cladding layers is analyzed and shown to contain information about the quality of the buried butt coupling. A ridge waveguide structure has successfully been fabricated from an optimized integrated laser / modulator structure.

We present a piezoelectrical shear-force distance control setup for scanning near-field optical microscopy. The setup is compact and tip exchange is easy. The topographical sensitivity is comparable to optical feedback systems. With an acceptable vibration amplitude of 5–10 nm we obtained a topographical resolution of 5 pm/ Hz . Because there is no laser necessary for tip position feedback, there is no extraneous light to interfere with spectroscopic and other low-light level experiments. Our technique permits measurements of soft biological samples in aqueous solution, which opens up many possible applications of near-field optical microscopy in biology and medicine.

Experiments using photons as a probe provide an excellent energy resolution. The wavelength of the light, however, sets a lower limit to the probed area perpendicular to the direction of propagation. This limit is of the order of the wavelength of the light. Scanning probe microscopes, on the other hand, have a superb spatial resolution. The energy of the interaction can only be acquired with modest sensitivity and resolution. Therefore, the combination of photons and local probes might provide the best of the two worlds. In this article we explore the possibilities of combining optical and SPM techniques. Near field optical microscopy using the aperture probe is used to investigate the emission properties of vertical cavity surface emitting laser diodes (VCSEL). Mode patterns put into relation to the topography of the emission area serve to diagnose the performance of the device. In contrast to classical optical microscopy techniques, our method is able to simultaneously decompose lasing transversal modes by their wavelength with lateral superresolution. Similarly, the comparison of the emission location of nanometer sized thin luminescent layers with the shape of the overgrown structure reveals variations of the bandgap and its position. Subtle differences in images obtained with internal and external collection modes provide clues to the diffusion of the charge carriers. Finally scanning force microscope (SFM) is used to detect near field light by a mechanism based on optical modulation of the image force between a semiconducting probe tip and a glass surface due to the surface photo-voltage (SPV). This technique, which has a lateral resolution of better than 70 nm, allows the simultaneous detection of minute optical powers as small as \(0.1pW/\sqrt {Hz}\) in air and of charges. The technique is applied to the measurement of optical and charge gratings of a photorefractive material.

Scanning Force Microscopes and Friction Force Microscopes are built in wide variety of designs. They have become welcome additions to industrial laboratories due to their ruggedness and because their measurement principle is, in many respects, a refinement of well established apparatus such as profilometers and tribometers. This article discusses the building blocks of scanning force microscopes.

It is often difficult to characterize and distinguish heterogeneous materials with domain sizes below 1 micrometer. The range between 1 nm and 1 μm lies in the crossover region where light scattering is applicable to the upper wavelength range and where x-ray and neutron scattering is strongest for the lower wavelength end. In addition the scattering methods require careful experimental procedures for a reconstruction of the real space structure. Scanning probe methods do provide a direct access to the surface properties in the range of interest. They are complementary to the recently developed x-ray imaging methods. In this paper we discuss the application of the scanning force and friction microscope and the near-field optical microscope to heterogeneous surfaces. The image formation process in both microscopes is different: the scanning force and friction microscope probes the nanomechanical properties of sample surfaces. The near-field optical microscope on the other hand measures the reflectivity, absorption or the fluorescence near the sample surface. As an application we discuss the imaging of polymer surfaces.

A scanning near-field optical microscope (SNOM), where the tip is scanned rather than the sample, is presented. The advantage of this ‘stand-alone’ type SNOM besides its compact setup is its ability to scan on arbitrarily extended samples. Furthermore, the sample can be manipulated during scanning (e.g. heated or extended), which may be of special interest in material sciences applications. An optical shear-force detection unit is implemented to control the tip-sample distance. Design problems specific to the stand-alone setup are discussed. Using uncoated fiber tips in reflection and transmission mode, lateral resolutions of better than 120 nm and 300 nm, respectively, are shown.

Scanning Force Microscopes are built in wide variety of designs. This article reviews setups and design concepts for contact and non-contact mode instruments and for friction mode instruments. The principles of operation of various designs is reviewed. The performance of scanning probe microscopes depends crucially on the mechanical properties of a particular design. In order to help users evaluate microscopes or to build them this article reviews some common design practices and rules.

We report on the growth of GaN in GSMBE using NH3 as nitrogen source. Special focus will be on the NH3 cracking, where we applied an On Surface Cracking technique (OSC). Using OSC we achieve photoluminescence linewidths as narrow as 5.5meV (5K) and mobilities of 220 cm2/Vs at room temperature.

The lateral force microscope has become an important tool for the study of friction at the atomic scale. Via local variations of the friction coefficient, a material contrast can be obtained. We describe a new design of a microscope consisting of a stand-alone head suited for use in air, liquid or electrolytic environment. Force calibration is discussed in detail. As an example for the performance of the instrument we show topographic and lateral force images of the crystal structure of mica.