Variable resistor made by repeated steps of epitaxial deposition and lithographic structuring of oxide layers by using wet chemical etchants

Variable resistors were constructed from epitaxial SrRuO3 (SRO), La0.67Sr0.33MnO3 (LSMO) and SrTiO3 layers with perovskite crystal structure. Each layer was patterned separately by lithographic methods. Optimized wet chemical etchants and several polishing steps in organic solvents allowed good epitaxy of subsequent layers, comparable to epitaxy on pristine substrates. Periodate as the oxidizing agent for SRO and iodide with ascorbic acid as the reducing agents for LSMO were used to attack these chemically resistant oxides. The final devices changed their conductance in a similar manner to previously described variable resistors that were defined with shadow masks

Photoresponsive Porphyrin Nanotubes of Meso-tetra(4-Sulfonatophenyl)Porphyrin and Sn(IV) meso-tetra(4-pyridyl)porphyrin

Porphyrin macrocycles and their supramolecular nanoassemblies are being widely explored in energy harvesting, sensor development, catalysis, and medicine because of a good tunability of their light-induced charge separation and electron/energy transfer properties. In the present work, we prepared and studied photoresponsive porphyrin nanotubes formed by the self-assembly of meso-tetrakis(4-sulfonatophenyl)porphyrin and Sn(IV) meso-tetra(4-pyridyl)porphyrin. Scanning electron microscopy and transmission electron microscopy showed that these tubular nanostructures were hollow with open ends and their length was 0.4–0.8 μm, the inner diameter was 7–15 nm, and the outer diameter was 30–70 nm. Porphyrin tectons, H4TPPS42- : Sn(IV)TPyP4+, self-assemble into the nanotubes in a ratio of 2:1, respectively, as determined by the elemental analysis. The photoconductivity of the porphyrin nanotubes was determined to be as high as 3.1 × 10−4 S m−1, and the dependence of the photoconductance on distance and temperature was investigated. Excitation of the Q-band region with a Q-band of SnTPyP4+ (550–552 nm) and the band at 714 nm, which is associated with J-aggregation, was responsible for about 34 % of the photoconductive activity of the H4TPPS42--Sn(IV)TPyP4+ porphyrin nanotubes. The sensor properties of the H4TPPS42-- Sn(IV)TPyP4+ nanotubes in the presence of iodine vapor and salicylate anions down to millimolar range were examined in a chemiresistor sensing mode. We have shown that the porphyrin nanotubes advantageously combine the characteristics of a sensor and a transducer, thus demonstrating their great potential as efficient functional layers for sensing devices and biomimetic nanoarchitectures

Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications

Application of photocurable polymers for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET) during the last 20 years is discussed. From a technological point of view these materials are quite interesting because they allow the use of standard photo-lithographic processes, which reduces significantly the time required for sensor encapsulation and membrane deposition and the amount of manual work required for this, all items of importance for sensor mass production. Problems associated with the application of this kind of polymers in sensors are analysed and estimation of future trends in this field of research are presented

Suspended Nanoporous Membranes as Interfaces for Neuronal Biohybrid Systems

A biohybrid system composed of neuronal cells and silicon-supported nanoporous membranes has been designed to facilitate control of the biochemical environment of neuronal networks with cellular resolution. The membranes may exhibit variable pore sizes and interpore distances and are interfaced to a microfluidic device. Different porosity parameters give rise to changes in the transconductance of the nanopores and can therefore be used to control diffusion of molecules through the membranes. It was shown that the porous membranes are biocompatible with primary vertebrate as well as insect neurons. Our results indicate that nanoporous membranes may be used to interface with biological materials in a biohybrid system, for example as an artificial chemical synapse interface

Electrochemical properties and biomimetic activity of water-soluble meso-substituted Mn(III) porphyrin complexes in the electrocatalytic reduction of hydrogen peroxide

The aim of this study was to investigate biomimetic activity of water-soluble manganese porphyrin complexes with a series of meso-substituents of the porphyrin macrocycle in the electrocatalytic reduction of hydrogen peroxide in aqueous solutions and to obtain information on possible intermediates, processes, and mechanisms. Mn porphyrins were compared in the process of the electrocatalytic reduction of hydrogen peroxide at pH 4, 7.4, and 10 in the deoxygenated solutions and in the presence of oxygen. The highest sensitivity, defined as the reduction current increase in relation to the concentration of hydrogen peroxide, was found in the case of Mn(III) meso-tetra(N-methyl-4-pyridyl) porphyrin, MnTMPyP, in alkaline 2.9·10−2 A M−1 and acidic 1.6·10−2 A M−1 solutions in the presence of oxygen. The reduction currents at pH 7.4, 10, and 4 in the presence of H2O2 were about 4, 7, and 12 times higher, respectively, in the solutions with the MnTMPyP complex than those at a GCE without a porphyrin complex in the solution. The electrocatalytic reduction of hydrogen peroxide occurs in parallel with an oxidative degradation of the porphyrin catalyst depending on the conditions of the experiment and was most significant in the presence of oxygen. The effect of the functional substituents at the meso-positions of a porphyrin ligand on the electrocatalytic activity of the water-soluble Mn(III) porphyrins complexes is discussed and reaction mechanisms are proposed

The evaporated metal masks for chemical glass etching for BioMEMS

Water consumed before a meal has been found to reduce energy intake among nonobese older adults. However, it is unknown whether this effect is evident among overweight and obese older adults, a population who would benefit from strategies to improve energy intake regulation. Our purpose was to determine whether premeal water consumption reduces meal energy intake in overweight and obese older adults. Twenty-four overweight and obese adults (body mass index=34.3+/-1.2), mean age 61.3+/-1.1 years, were given an ad libitum standardized breakfast meal on two randomly assigned occasions. Thirty minutes before the meal, subjects were given either a 500-mL water preload or no preload. Energy intake at each meal was covertly measured. Meal energy intake was significantly less in the water preload condition as compared with the no-preload condition (500+/-32 vs 574+/-38, respectively; P=0.004), representing an approximate 13% reduction in meal energy intake. The percentage reduction in meal energy intake following the water preload was not related to sex, age, body mass index, or habitual daily water consumption (all P>0.05). Given the high prevalence of overweight and obesity among older adults, future studies should determine whether premeal water consumption is an effective long-term weight control strategy for older adults