Biophotonic sensors with integrated Si3N4-organic hybrid (SiNOH) lasers for point-of-care diagnostics.

Early and efficient disease diagnosis with low-cost point-of-care devices is gaining importance for personalized medicine and public health protection. Within this context, waveguide-(WG)-based optical biosensors on the silicon-nitride (Si3N4) platform represent a particularly promising option, offering highly sensitive detection of indicative biomarkers in multiplexed sensor arrays operated by light in the visible-wavelength range. However, while passive Si3N4-based photonic circuits lend themselves to highly scalable mass production, the integration of low-cost light sources remains a challenge. In this paper, we demonstrate optical biosensors that combine Si3N4 sensor circuits with hybrid on-chip organic lasers. These Si3N4-organic hybrid (SiNOH) lasers rely on a dye-doped cladding material that are deposited on top of a passive WG and that are optically pumped by an external light source. Fabrication of the devices is simple: The underlying Si3N4 WGs are structured in a single lithography step, and the organic gain medium is subsequently applied by dispensing, spin-coating, or ink-jet printing processes. A highly parallel read-out of the optical sensor signals is accomplished with a simple camera. In our proof-of-concept experiment, we demonstrate the viability of the approach by detecting different concentrations of fibrinogen in phosphate-buffered saline solutions with a sensor-length (L-)-related sensitivity of S/L = 0.16 rad nM-1 mm-1. To our knowledge, this is the first demonstration of an integrated optical circuit driven by a co-integrated low-cost organic light source. We expect that the versatility of the device concept, the simple operation principle, and the compatibility with cost-efficient mass production will make the concept a highly attractive option for applications in biophotonics and point-of-care diagnostics.

Lasing in Si3N4-organic hybrid (SiNOH) waveguides.

Silicon nitride (Si3N4) waveguides offer low-loss wave propagation over a wide spectral range including visible wavelengths and lend themselves to photonic integrated circuits for bio-photonic applications. The Si3N4 device portfolio, however, is so far limited to passive devices that need to be fed by external light sources. This often requires delicate and costly fiber-chip coupling schemes that are subject to stringent alignment tolerances. In this paper, we present and investigate a class of lasers that combine Si3N4 waveguides with light-emitting organic cladding materials in a hybrid approach. These Si3N4-organic hybrid (SiNOH) lasers are operated by optical pumping from the top with low alignment precision. We theoretically and experimentally investigate different SiNOH laser concepts based on spiral-shaped ring resonators and distributed feedback (DFB) resonators. While our devices are designed for an emission wavelength of approximately 600 nm, the SiNOH laser concept can be transferred to a large range of wavelengths in the visible spectrum. The devices are amenable to cost-efficient mass production and have the potential to address a wide range of applications in bio-photonics and point-of-care diagnostics.

Configurable Resistive Response in BaTiO3 Ferroelectric Memristors via Electron Beam Radiation.

Ferroelectric oxide memristors are currently in the highlights of a thriving area of research aiming at the development of nonvolatile, adaptive memories for applications in neuromorphic computing. However, to date a precise control of synapse-like functionalities by adjusting the interplay between ferroelectric polarization and resistive switching processes is still an ongoing challenge. Here, it is shown that by means of controlled electron beam radiation, a prototypical ferroelectric film of BaTiO3 can be turned into a memristor with multiple configurable resistance states. Ex situ and in situ analyses of current/voltage characteristics upon electron beam exposure confirm the quasi-continuous variation of BaTiO3 resistance up to two orders of magnitude under the typical experimental conditions employed in electron beam patterning and characterization techniques. These results demonstrate an unprecedented effective route to locally and scalably engineering multilevel ferroelectric memristors via application of moderate electron beam radiation.

High-flexibility combinatorial peptide synthesis with laser-based transfer of monomers in solid matrix material.

Laser writing is used to structure surfaces in many different ways in materials and life sciences. However, combinatorial patterning applications are still limited. Here we present a method for cost-efficient combinatorial synthesis of very-high-density peptide arrays with natural and synthetic monomers. A laser automatically transfers nanometre-thin solid material spots from different donor slides to an acceptor. Each donor bears a thin polymer film, embedding one type of monomer. Coupling occurs in a separate heating step, where the matrix becomes viscous and building blocks diffuse and couple to the acceptor surface. Furthermore, we can consecutively deposit two material layers of activation reagents and amino acids. Subsequent heat-induced mixing facilitates an in situ activation and coupling of the monomers. This allows us to incorporate building blocks with click chemistry compatibility or a large variety of commercially available non-activated, for example, posttranslationally modified building blocks into the array's peptides with >17,000 spots per cm(2).

Particle-Based Microarrays of Oligonucleotides and Oligopeptides.

In this review, we describe different methods of microarray fabrication based on the use of micro-particles/-beads and point out future tendencies in the development of particle-based arrays. First, we consider oligonucleotide bead arrays, where each bead is a carrier of one specific sequence of oligonucleotides. This bead-based array approach, appearing in the late 1990s, enabled high-throughput oligonucleotide analysis and had a large impact on genome research. Furthermore, we consider particle-based peptide array fabrication using combinatorial chemistry. In this approach, particles can directly participate in both the synthesis and the transfer of synthesized combinatorial molecules to a substrate. Subsequently, we describe in more detail the synthesis of peptide arrays with amino acid polymer particles, which imbed the amino acids inside their polymer matrix. By heating these particles, the polymer matrix is transformed into a highly viscous gel, and thereby, imbedded monomers are allowed to participate in the coupling reaction. Finally, we focus on combinatorial laser fusing of particles for the synthesis of high-density peptide arrays. This method combines the advantages of particles and combinatorial lithographic approaches.

Effect of the silicone disclosing procedure on the shear bond strength of composite cements to ceramic restorations.

STATEMENT OF PROBLEM: There is no evidence-based information on how ceramic restorations with an adhesive bond between restoration material and composite cement may be influenced by a silicone disclosing agent. PURPOSE: The aim of this study was to determine the effects of the silicone disclosing procedure on the shear bond strength of composite cements in the luting of industrial sintered and laboratory sintered ceramic restorations. MATERIAL AND METHODS: Thirty standardized (15 x 10 x 9 mm) prefabricated ceramic specimens (Groups 1, 3, 5) and 30 standardized (15 x10 x 9 mm) conventionally sintered ceramic specimens (Groups 2, 4, 6) were roughened with sandpaper (800-grit). Each group contained 10 specimens. Groups 3 and 4 were conditioned with hydrofluoric acid and primed with silane solution after the use of a silicone disclosing procedure. Groups 1 and 2 served as the control groups, where no silicone disclosing procedure was performed. Groups 5 and 6 were insulated with glycerine before the silicone disclosing procedure. A glass tube (4.5 mm in diameter) was used to apply a cylinder of dual-polymerized composite cement to the conditioned surfaces. All specimens were submitted to 5000 thermocycles (5 degrees to 55 degrees C) to simulate the in vivo situation. The specimens were subjected to a shear-pull test at a constant crosshead speed of 5 mm/min with a universal testing machine. The comparative shear bond strengths were analyzed by use of Duncan's test (alpha=0.05). RESULTS: Shear bond strength values for Groups 1 (9.86 +/- 4.97 MPa) and 2 (9.56 +/- 4.47 Mpa) were obtained with no significant differences. Lower but significantly undifferent values were obtained for Groups 3 (7.49 +/- 4.67 MPa) and 4 (7.62 +/- 3.49 MPa) after the use of a silicone disclosing procedure. In Groups 5 (8.21 +/- 4.75 MPa) and 6 (8.22 +/- 3.59 MPa), including insulation with glycerine before the silicone disclosing procedure, no significant differences were obtained. CONCLUSION: Within the limitations of this study, the use of silicone disclosing procedures before conditioning the ceramic surface did not lead to a significant reduction of the shear bond strength between ceramic and composite cement. The ceramic materials used (industrial-sintered versus laboratory-sintered ceramic) had no significant influence on adhesion.