Ink transport modelling in Dip-Pen Nanolithography and Polymer Pen Lithography

Dip-pen nanolithography (DPN) and Polymer pen lithography (PPL) are powerful lithography techniques being able to pattern a wide range of inks. Transport and surface spreading depend on the ink physicochemical properties, defining its diffusive and fluid character. Structure assembly on surface arises from a balance between the entanglement of the ink itself and the interaction with the substrate. According to the transport characteristics, different models have been proposed. In this article we review the common types of inks employed for patterning, the particular physicochemical characteristics that make them flow following different dynamics as well as the corresponding transport mechanisms and models that describe them

FluidFM-Based Fabrication of Nanopatterns: Promising Surfaces for Platelet Storage Application

Platelets are cell fragments from megakaryocytes devoid of the cell nucleus. They are highly sensitive and easily activated by nonphysiological surfaces. Activated platelets have an intrinsic mechanism to release various proteins that participate in multiple pathways, initiating the platelet activation cascade. Surface-induced platelet activation is a challenge encountered during platelet storage, which eventually leads to aggregation of platelets and can thereby result in the degradation of the platelet concentrates. We have previously reported that surface-induced platelet activation can be minimized by either modifying their contact surfaces with polymers or introducing nanogroove patterns underneath the platelets. Here, we investigated the response of platelets to various nanotopographical surfaces printed using fluidic force microscopy (FluidFM). We found that the hemispherical array (grid) and hexagonal tile (hive) structures caused a reduction of surface stiffness, which leads to an inhibition of platelet adhesion. Our results reveal that nanopatterns enable the inhibition of platelet activation on surfaces, thus implying that development in nanotexturing of storage bags can extend the lifetime of platelet concentrates

Computergestützte Zahnbogenformberechnungen zur Verbesserung der Ergebnisqualität in der Orthodontie

Die drei Zielsetzungen dieser Arbeit sind erstens ein umfassender Review internationaler Literatur zum Thema "Humane Zahnbogenformen", zweitens die Entwicklung einer Klassifikation der mathematischen Modelle zur computergestützten Berechnung von Zahnbogenformen mit einer Systematik als Entscheidungshilfe für die Auswahl mathematischer Formeln bei spezifischen klinischen und wissenschaftlichen Fragestellungen; als drittes umfasst diese Arbeit die Konzeption, einschließlich der Programmierung und Pilotierung des Computerprogramms "Dental Archform Manager (DAM)", welches dem klinisch tätigen Fachzahnarzt für Kieferorthopädie ein leistungsfähiges digitales Werkzeug zur Dokumentation und virtuellen Planung der in der Multibracketbehandlung therapeutisch relevanten Zahnbogenformen zur Verfügung stellt. Gleichzeitig wurden die Bogenformen führender Hersteller konfektionierter Behandlungsbögen im Hinblick auf die Verwendung innerhalb dieser Software analysiert und pragmatisch gruppiert

How Does Chemistry Influence Liquid Wettability on Liquid-Infused Porous Surface?

Design of Nepenthes pitcher-inspired slippery liquid-infused porous surface (SLIPS) appeared as an important avenue for various potential and practically relevant applications. In general, hydrophobic base layers were infused with selected liquid lubricants for developing chemically inert SLIPS. Here, in this current study, an inherently hydrophilic (soaked beaded water droplet with ∼20° within a couple of minutes), porous and thick (above 200 μm) polymeric coating, loaded with readily chemically reactive acrylate moieties yielded a chemically reactive SLIPS, where residual acrylate groups in the synthesized hydrophilic and porous interface rendered stability to the infused lubricants. The chemically reactive SLIPS is capable of reacting with the solution of primary amine-containing nucleophiles in organic solvent through 1,4-conjugate addition reaction, both in the presence (referred as “in situ” modification) and absence (denoted as pre-modification) of lubricated phase in the porous polymeric coating. Such amine reactive SLIPS was further extended to (1) examining the impact of different chemical modifications on the performance of SLIPS and (2) developing a spatially selective and “in situ” postmodification with primary amine-containing nucleophiles through 1,4-conjugate addition reaction. Moreover, the chemically reactive SLIPS was capable of sustaining various physical abrasions and prolonged (minimum 10 days) exposure to complex and harsh aqueous phases, where infused lubricants protect the residual acrylate groups from harsh aqueous exposures. Such, principle will be certainly useful for spatially selective covalent immobilization of water-insoluble functional molecules/polymers directly from organic solvents, which would be of potential interest for various applied and fundamental contexts

A supramolecular cucurbit[8]uril-based rotaxane chemosensor for the optical tryptophan detection in human serum and urine

Sensing small biomolecules in biofluids remains challenging for many optical chemosensors based on supramolecular host-guest interactions due to adverse interplays with salts, proteins, and other biofluid components. Instead of following the established strategy of developing alternative synthetic binders with improved affinities and selectivity, we report a molecular engineering approach that addresses this biofluid challenge. Here we introduce a cucurbit[8]uril-based rotaxane chemosensor feasible for sensing the health-relevant biomarker tryptophan at physiologically relevant concentrations, even in protein- and lipid-containing human blood serum and urine. Moreover, this chemosensor enables emission-based high-throughput screening in a microwell plate format and can be used for label-free enzymatic reaction monitoring and chirality sensing. Printed sensor chips with surface-immobilized rotaxane-microarrays are used for fluorescence microscopy imaging of tryptophan. Our system overcomes the limitations of current supramolecular host-guest chemosensors and will foster future applications of supramolecular sensors for molecular diagnostics

Cucurbit[n]uril-Immobilized Sensor Arrays for Indicator-Displacement Assays of Small Bioactive Metabolites

The patterned immobilization of chemosensors into nano/microarrays has often boosted utilization in diagnostics and environmental sensing applications. While this is a standard approach for biosensors, e.g., with antibodies, other proteins, and DNA, arraying is not yet adopted widely for supramolecular chemosensors which are still predominantly used in solution systems. Here we introduce the patterned immobilization of cucurbit[n]urils (CBn) into multiplexed microarrays and elucidate their prospects for the advancement of surface-bound indicator-displacement assays to detect small molecule analytes. The microarrays were generated by microchannel cantilever spotting of functionalized CBn and subsequent self-assembly of the corresponding indicator dyes from solution. Enhanced sensitivity of surface-bound microarrays was established in demonstrations with small bioactive metabolites (spermine, amantadine, and cadaverine) compared to bulk assays. Furthermore, the integration of the CBn/indicator microarrays into microfluidic channels provides an efficient route for real-time monitoring of the sensing process, allows easier handling, and reduces need for analyte volume. The concept was further extended to differential sensing of analytes on diplex or multiplex CBn/indicator microarrays, opening up a route for multicomponent sensing of small molecule analytes in complex liquids

Integration of Biofunctional Molecules into 3D-Printed Polymeric Micro-/Nanostructures

Three-dimensional printing at the micro-/nanoscale represents a new challenge in research and development to achieve direct printing down to nanometre-sized objects. Here, FluidFM, a combination of microfluidics with atomic force microscopy, offers attractive options to fabricate hierarchical polymer structures at different scales. However, little is known about the effect of the substrate on the printed structures and the integration of (bio)functional groups into the polymer inks. In this study, we printed micro-/nanostructures on surfaces with different wetting properties, and integrated molecules with different functional groups (rhodamine as a fluorescent label and biotin as a binding tag for proteins) into the base polymer ink. The substrate wetting properties strongly affected the printing results, in that the lateral feature sizes increased with increasing substrate hydrophilicity. Overall, ink modification only caused minor changes in the stiffness of the printed structures. This shows the generality of the approach, as significant changes in the mechanical properties on chemical functionalization could be confounders in bioapplications. The retained functionality of the obtained structures after UV curing was demonstrated by selective binding of streptavidin to the printed structures. The ability to incorporate binding tags to achieve specific interactions between relevant proteins and the fabricated micro-/nanostructures, without compromising the mechanical properties, paves a way for numerous bio and sensing applications. Additional flexibility is obtained by tuning the substrate properties for feature size control, and the option to obtain functionalized printed structures without post-processing procedures will contribute to the development of 3D printing for biological applications, using FluidFM and similar dispensing techniques

Covalently Modulated and Transiently Visible Writing: Rational Association of Two Extremes of Water Wettabilities

Anticounterfeiting measures are of ever-increasing importance in society, e.g., for securing the authenticity of and the proof of origin for medical drugs. Here, an arms race of counterfeiters and valid manufacturers is taking place, resulting in the need of hard-to-forget, yet easy-to-read out marks. Anticounterfeiting measures based on micropatterns—while being attractive for their need in not widely available printing methods while still being easily read out with fairly common basic optical equipment—are often limited by being too easy to be destroyed by wear or handling. Here, nature-inspired wettability is rationally exploited for developing an unprecedented anticounterfeiting method, where hidden information can be only identified under direct exposures to an aqueous phase or mist and disappears again on air-drying the interface. A chemically reactive and hierarchically featured dip coating, capable of spatially selective covalent modification with primary amine containing small molecules, is developed for abrasion-tolerant patterning interfaces with two extremes of water wettabilities, i.e., superhydrophilicity and superhydrophobicity. Arbitrary handwriting with glucamine followed by chemical modification with octadecylamine, provided “invisible” text on the synthesized interface. The glucamine-treated region selectively becomes optically transparent and superhydrophilic due to rapid infiltration of the aqueous phase on exposure to liquid water or mist. The remaining interface remains opaque and superhydrophobic due to metastable entrapment of air. The hidden text became transiently and reversibly visible by the naked eye under exposure to liquid water/mist. Furthermore, microchannel-cantilever spotting (μCS) is adopted for demonstrating well-defined chemical patterning on the microscale. These patterns are at the same time highly resistant against wear and scratching because of the bulk functionalization, retaining the wetting properties (and thus pattern readout) even on serious abrasion. Such a simple synthesis of spatially controlled, direct, and covalently modulated wettability could be useful for various applied and fundamental contexts