Nickel’s durability and catalytic properties make it essential in the aerospace, automotive, electronics, and fuel cell technology industries. Wastewater analysis typically relies on sensitive but costly techniques such as ICP-MS, AAS, and ICP-AES, which require complex equipment and are unsuitable for on-site testing. This study introduces a novel screen-printed electrode array with 16 chemically and, optionally, electrochemically coated Au electrodes. Its electrochemical response to Ni2+ was tested using Na2SO3 and ChCl-EG deep eutectic solvents as electrolytes. Ni2+ solutions were prepared from NiCl2·6H2O, NiSO4·6H2O, and dry NiCl2. In Na2SO3, the linear detection ranges were 20–196 mM for NiCl2·6H2O and 89–329 mM for NiSO4·6H2O. High Ni2+ concentrations (10–500 mM) were used to simulate industrial conditions. Two linear ranges were observed, likely due to differences in electrochemical behaviour between NiCl2·6H2O and NiSO4·6H2O, despite the identical Na2SO3 electrolyte. Anion effects (Cl− vs. SO42−) may influence response via complexation or ion pairing. In ChCl-EG, a linear range of 0.5–10 mM (R2 = 0.9995) and a detection limit of 1.6 µM were achieved. With a small electrolyte volume (100–200 µL), nickel detection in the nanomole range is possible. A key advantage is the array’s ability to analyze multiple analytes simultaneously via customizable electrode configurations. Future research will focus on nickel detection in industrial wastewater and its potential in the multiplexed analysis of toxic metals. The array also holds promise for medical diagnostics and food safety applications using thiol/Au-based capture molecules.

As part of the ongoing evolution towards personalized anticancer therapy, mutation screening is becoming increasingly important and, therefore, also alternative detection strategies that allow for fast genetic diagnostics at the point of care. In the case of breast cancer, detecting cancer-associated point mutations in the PIK3CA gene is of particular importance for treatment decisions. We developed a recombinase polymerase amplification assay combined with an enzyme-linked electrochemical assay on multi-channel screen-printed gold sensors for specific and highly sensitive detection of three PIK3CA point mutations (H1047R, E545K, and E542K). Recombinase polymerase amplification (RPA) of the target sequences was optimized and characterized with a real-time RPA assay. Comparison with real-time PCR reveals that RPA is slightly inferior in terms of efficiency and sensitivity. However, the desired target DNA is successfully amplified at initial concentrations down to 100 copies μL−1. For electrochemical readout, biotinylated dCTP is used to label the target DNA during RPA. Single-stranded target DNA is produced with either asymmetric RPA or symmetric RPA followed by lambda exonuclease digestion. Characterization of the two different approaches in terms of sensitivity results in comparable detection limits (229 copies μL−1 and 224 copies μL−1, respectively), though RPA followed by lambda exonuclease digestion yields significantly higher currents. Finally, this method, together with a designed wild-type blocking oligo that inhibits binding of the wild-type target DNA during probe-target hybridization, allows for detecting the PIK3CA point mutations H1047R, E545K, and E542K in the presence of wild-type target DNA when the proportion of mutant target DNA is >20%.

Screen-printed electrochemical sensors have gained considerable research interest in recent years due to their favorable properties in terms of sensitivity, analysis time, instrumentational simplicity, and cost-efficiency, which make them ideally suited for point-of-care testing applications. Electrochemical DNA sensors are of particular interest due to the important role of nucleic acids as biomarker in disease diagnostics. As a result, a wide variety of novel electrochemical DNA sensing approaches have already been developed to allow, e.g., for the detection of viral or bacterial nucleic acids, but also for the rather challenging detection of cancer-related point mutations, which requires exceptionally high level of selectivity. Many of the developed electrochemical DNA detection approaches rely on the use of DNA-binding redox indicators, the prerequisite being a different interaction of these compounds with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). We investigated the suitability of the commonly used DNA-binding redox indicators ruthenium(III) hexaammine, methylene blue, anthraquinone-2-sulfonic acid (AQMS), and anthraquinone-2,6-disulfonic acid (AQDS) for electrochemical detection of DNA hybridization on screen-printed sensors via differential pulse voltammetry. For none of the tested redox indicators we observed a significant signal difference between ssDNA and dsDNA that would allow for detecting DNA hybridization. In contrast, a horseradish peroxidase (HRP)-based enzyme-linked electrochemical assay proved suitable for sensitive and specific target DNA detection due to the inherent advantages of enzymatic signal amplification and negligible current response in the absence of target DNA.

Screen-printed electrochemical sensors are of particular interest for point-of-care diagnostic applications due to their high sensitivity, short analysis times, and cost-efficient large-scale fabrication. Especially noble metal-based sensors offer the possibility of easy surface modification via self-assembly of thiol-labelled compounds. We examined silver, gold, and palladium as electrode materials regarding their suitability for highly specific and sensitive DNA detection with a chronoamperometric enzyme-amplified electrochemical assay. Modification with either gold nanoparticles or silver-coated microbeads was tested as a possibility to improve the performance of the electrochemical sensors. The sensors were characterized regarding surface topography, sensitivity towards the redox-active substrate TMB, efficiency of capture probe immobilization, as well as mutation specificity. The highest sensitivity for oxidized TMB was observed for gold sensors that yielded a limit of detection of 2.1 mu M, while no improvement in sensitivity was observed for sensors modified with gold nanoparticles or silver-coated microbeads. DNA probe immobilization and multiplexed target DNA detection was successful with all tested electrode materials. However, modification with silver-coated microbeads led to both reduced probe immobi-lization efficiency and hybridization specificity. Gold nanoparticle modification of both silver and of gold sensors induced a highly porous sensor surface after sintering, which increases the surface area of the electrodes. The gold nanoparticle modified sensors showed particularly appreciable results in terms of improved hybridization specificity, as demonstrated by successful multiplexed detection of three PIK3CA point-mutations (H1047R, E545K, and E542K). Average discrimination factors D of 2.7 and 2.1 were obtained for gold and silver sensors modified with one layer of gold nanoparticles, respectively.

For anticancer therapy and disease prognosis in breast cancer, three PIK3CA point-mutations (H1047R, E545K, and E542K) play a significant role. To allow for specific and sensitive detection of these point-mutations with a hybridization-based detection concept, the assay conditions were optimized on a microarray technology platform. The resulting fluorescence-based microarray assay enables simultaneous and specific detection of three PIK3CA point-mutations. The optimized protocol was then adapted for use on a screen-printed and gold-plated silver sensor array with twelve working electrodes, one common counter electrode, and one common reference electrode. Chronoamperometric measurements employing an enzyme-amplified electrochemical assay allow for detecting PIK3CA point-mutations with a detection limit of 10 pM for short 24-mer target DNA. The mutant and the wild-type target DNA sequences gave significantly different signals in a broad concentration range of 1 nM – 100 nM, with the best separation found at 10 nM – 20 nM. Comparing the hybridization of short 24-mer and long 80-mer target DNA sequences reveals that the hybridization efficiency is reduced for long target DNA sequences. However, both the 24-mer and the 80-mer target DNA lead to successful detection of point-mutations. Finally, the electrochemical sensor allows for multiplexed detection of the three PIK3CA point-mutations.

Amperometric sensors can be used for many applications, as they can be excellently manufactured in roll-to-roll printing processes. However, careful material selection is of particular importance for high sensitivity and selectivity. For example, the choice of the reference electrode material is critical to ensure a stable electrical potential, and the working electrode material needs to match the redox system used. For biosensor applications, the immobilization of the receptor molecules via printing technologies must be ensured, for which again the sensor materials significantly contribute. To illustrate these challenges, examples are presented for the detection of small molecules, proteins and DNA.

The growing miniaturization of electronic components increases the local heat emission per unit square and PCBs are a critical bottleneck in thermal terms. The integration of the electronic components into the heatsink material surface itself becomes a necessity. Therefore, electric isolation layers with a high thermal conductivity are needed. In this work, isolation layers were fabricated using plasma-electrolytic oxidized Al substrates. Since such layers are porous in general, a polyamide-imide resin was used to increase the electric breakdown voltage while simultaneously only minimal influences the thermal conductivity. The thermal conductivity of the layers were quantified by use of a 3-omega measurement approach. A heating element structure was evaporated on the surface and a sinusoidal current was applied. The higher harmonics of the resulting voltage across the heater is an indication for the thermal conductivity of the isolation layer. The measurement approach was verified with a commercial available insulated metallic substrate and the fabricated layer system exhibits thermal conductivities of 2.4 W/(mK). Additionally, finite element method models were used to investigate the influence of complex heater geometries, such as constrictions and holes in the heating element that occur due to the rough surfaces.

Air conditioning systems need permanent monitoring of the mass and energy flows in air ducts to assess their proper operation and detect and correct changes that may occur with time. This is a prerequisite for optimization in terms of energy efficiency. Such distributed monitoring systems require low-cost and robust flow sensors that must not be extremely precise, but give a good indication of the flow distribution within the air conditioning system. In this paper we present a novel flow sensor based on thick-film thermopiles deposited by silk-screen-printing on a plastic carrier. The flexible printed thermopile transducer was characterised in a flow channel to demonstrate the feasibility of the technology for air conditioning systems. The transducer exhibits a strictly increasing behaviour with increasing flow velocity, which is in good agreement to FEM simulations.

Resonance enhanced absorption (REA) nanocolor microfluidic devices are new promising bioassay platforms, which employ nanoparticle- (NP-) protein conjugates for the immunodetection of medically relevant markers in biologic samples such as blood, urine, and saliva. The core component of a REA test device is a PET chip coated with aluminum and SiO2 thin layers, onto which biorecognitive molecules are immobilized. Upon addition of a sample containing the analyte of interest, a NP-protein-analyte complex is formed in the test device that is captured on the REA chip, for example, via streptavidin-biotin interaction. Thereby, a colored symbol is generated, which allows optical readout. Silver enhancement of the bound nanoparticles may be used to increase the sensitivity of the assay. Herein, we demonstrate that adsorptive immobilization via a cationic polymeric interlayer is a competitive and fast technique for the binding of the capture protein streptavidin onto planar SiO2 surfaces such as REA biochips. Moreover, we report the development of a silver enhancement technology that operates even in the presence of high chloride concentrations as may be encountered in biologic samples. The silver enhancement reagents may be integrated into the microfluidic assay platform to be released upon sample addition. Hereby, a highly sensitive one-step assay can be realized.

Air conditioning systems need permanent monitoring of the mass and energy flows in the air ducts to assess their proper operation and detect and correct changes that may occur over time. This is a prerequisite for energy efficiency and demanded by recent legislation like the Energy Performance of Buildings Directive issued by the European Union. Such distributed monitoring systems require low-cost and robust flow sensors that need not be extremely precise, but should give a good indication of the flow distribution within the air conditioning system. In this paper we present a technology feasibility study to implement flow sensors based on thick-film thermopiles printed by silk screen printing on a plastic carrier film. Finite element simulation studies prove the viability of the sensor concept, and first samples of the printed Ag-Ni thermopiles demonstrate the feasibility of the production technology.

. The most fundamental properties of metal nanoclusters, namely the high local-field enhancement and nanoscale resonance behavior of the cluster electron plasma when exited by electromagnetic radiation, have been used to set up a variety of sensors transducing biorecognitive interactions into optical signals. This paper focuses on applications of resonant-cluster technology, which enabled us to monitor biorecognitive binding of a variety of proteins on a chip, thus constructing high-throughput interaction-screening devices. Decisive for this type of sensor is the nanometric distance from the local field surrounding a cluster to other parts of the sensor interacting with this field. In particular, the cluster–mirror or cluster–fluorophore distance gives rise to a variety of enhancement phenomena. Depending on the desired application this "resonance" – distance is approximately 5–400 nm. All types of sensor can be set up on photolithographically constructed microchips, but microscopic glass slides can also be employed; this also enables the use of standard devices for dotting and read out. Using slide based chips a standard format of 3200 microdots (125 µm in diameter) was the basis of either microassays applying direct optical transduction via surface-enhanced absorption or striking for more sensitivity via surface-enhanced fluorescence.

Through a novel immunoassay nanoparticles (NPs) are captured via immune-reactive proteins and positioned as a sub-monolayer just a few nanometres above a light reflective surface. Here the particles and the mirror form a nanometric interference system with a tuneable colour throughout the full spectrum of light. This concept, which was inspired by nature (‘wings of a butterfly’), creates an intensive colour clearly visible to the eye. By adaptation of this technique point-of-care (POC) tests become more sensitive, specific and time efficient. The novel format employs a combination of microfluidics and ‘resonance-enhanced absorption’ (REA) of gold and palladium nanoparticles quantifying interleukin-6 as an important parameter of acute sepsis. The colour intensity of the rapid test is boosted by using a subsequent silver enhancement. This performed in situ in just two to three minutes and a sensitivity of < 500 pg/ml was obtained.

L'invention concerne un papier, du carton, des cartons ondules, des films, des pieces en matiere plastique moulees par injection ou sous pression, du metal, des surfaces ceramiques, des couches de peinture ou des couches anti-corrosion, revetus d'un melange comprenant au moins un sel de molybdene, choisi dans le groupe molybdates, silicomolybdates ou phosphomolybdates d'ammonium, d'alkylamine ou alcalins, ou composes de tungstene ou de vanadium analogues, et d'une couche de couverture en materiau transparent organique ou silico-organique, la structure globale pouvant, sous l'effet de la lumiere, subir une modification de couleur, de maniere definie dans l'espace et structuree, reconnaissable par l'oeil humain.

The effectiveness of a novel multicolor biochip boosted by reducing cluster repulsion and in-situ silver enhancement has been demonstrated by using anti-serum albumine antibodies conjugated to gold nanoparticles on a vacuum metalized plastic film coated with nano-resonance driving ceramic multilayers. A dense and smooth vacuum deposited SiO approximately 1.6 top layer (50 to 300 nm thick) on a flexible thermoplastic polymer poly-ethylene-terephthalate-chip functionalized via poly-ethylenimine monolayer coating and chemical cross-linking was employed to immobilize capture antibodies. Following capturing of the human serum albumin antigen from analyte solution, the multicolor chip reacts with anti HSA-gold nanoparticles binding them in a nanometric distance to the resonant mirror of the device-visible to the eye as faint coloring of the chip surface. Following silver enhancement, a strong metallic angle-dependent color via Resonance Enhanced Absorption is observed. In this study, silver staining has been used for the first time to boost and shift the color of nano-resonance enhanced optical bioassays. The use of silver staining increases and significantly modifies the intensity of the resonance color and was done in less than 5 minutes directly on the chip. This novel methodology will find broad application in Point-of-Care diagnostic devices via a color signal output designed as a written text with high contrast to replace standard lateral flow devices just showing lines or dots.