Challenging material patterning: fine lithography on coarse substrates.

Precise patterning of inorganic materials is important for many technological applications. Often lithography processes are required on challenging substrates with respect to topography, flexibility, and surface adhesion. Here we show the fabrication of artificial gunshot residues (GSR) on adhesive tape samples by means of dip-pen lithography as an example for fine lithography on coarse substrates. We deposited lead-, barium-, and antimony-containing inks on SEM adhesive tape by direct writing with a fine tip. Single as well as multiple element structures with dimensions in the range of 10-75 µm were fabricated.

Dip-pen-based direct writing of conducting silver dots.

Direct fabrication of micro- and nanoscale metallic structures is advantageous for many applications. Here, we use dip-pen lithography with silver(I) carboxylate [AgO2C(CH2OCH2)3H] in diethylene glycol as precursor ink for the generation of conducting metal structures. After annealing the written dots, solid silver structures are generated. We investigate the influence of several parameters such as substrate functionalization and ink composition on the pattern formation. We found that a substrate coating with perfluorinated silane is necessary, if diethylene glycol will be used as ink carrier. By variation in ink concentration and ink carrier composition, structures with diameters ranging from ~20 µm to ~2 µm and with metal fractions ranging from ~5% to ~80% were fabricated. After gold enhancement of the written patterns, resistivities in the range of 4×10(-5) Ωm on the structures were determined. The ink system introduced here appears promising for the direct fabrication of various metal or metal oxide patterns.

Control of cell adhesion and neurite outgrowth by patterned gold nanoparticles with tunable attractive or repulsive surface properties.

Guiding of neuronal cells on surfaces is required for the investigation of fundamental aspects of neurobiology, for tissue engineering, and for numerous bioelectronic applications. A modular method to establish nanostructured chemical templates for local deposition of gold nanoparticles is presented. A process comprising nanoimprint lithography, silanization, lift-off, and gold nanoparticle immobilization is used to fabricate the particle patterns. The chemical composition of the surface can be modified by in situ adsorption of cell-binding ligands to locally addressed particles. The versatility of this approach is demonstrated by inverting the binding affinity between rat cortical neurons and nanopatterned surfaces via wet-chemical means and thereby reversing the pattern of guided neurons.

Deformation of nanostructures on polymer molds during soft UV nanoimprint lithography.

Soft nanoimprint lithography (soft NIL) relies on a mechanical deformation of a resist by a patterned polymer used as a mold. Here, we report on the investigation of the nanopattern fidelity of the high pressure imprint process based on a perfluorinated polyether (PFPE) soft mold material. The perfluorinated polyether material was found to be well suited to transfer the mold pattern into the resist by a direct imprinting process at low cost. Moderate deformations of the polymer mold structures occurring during the high pressure imprint are systematically studied. Features of decreased size are found to be more sensitive to pattern distortions. An optimized pattern design with increased structure density and constant pattern ratio is developed to minimize deformation effects. Imprints performed on the basis of these design rules result in reduced deformations and repeal their size dependence. The improved pattern transfer, especially for small structural elements, turns the direct and cost-effective soft UV-NIL into an interesting technique also for patterning tasks in the lower nanometer range.

The effect of a model-based predictive display on the control of end-tidal sevoflurane concentrations during low-flow anesthesia.

We have shown that a multicompartment model accurately predicts end-tidal (ET) sevoflurane (sevo) and isoflurane concentrations. The model has been adapted to use real-time fresh gas flow and vaporizer settings to display a 10-min prediction of ET sevo concentrations. In this study, we evaluated the effect of the predictive display on the speed and accuracy of changes in ET sevo by the anesthesiologist. Fifteen patients were studied in whom sevo-based anesthesia was expected to last more than 2 h. Four step changes of target ET concentration (+0.5, +1.0, -1.0, and -0.5 vol%) were made either unaided or with the prediction display. Fresh gas flow was 1 L/min. Response time, maximum overshoot, and stability in the 5 min after the target was achieved were compared by using two-tailed paired Student's t-tests. Changes were made on average 1.5-2.3 times faster with the predictive display than without it. These differences were statistically significant (P < 0.05) for the +0.5, +1.0, and -0.5 vol% step changes but not for the -1.0 vol% change. There were no differences in the degree of overshoot or stability. These differences are comparable to those seen with an automatic feedback control system. This system may simplify the administration of volatile anesthesia and the use of low-flow anesthesia.