A novel silicon on insulator (SOI) MEMS process has been designed and developed to realize a two axes thermally actuated single crystal silicon micromirror device, which consists of a mirror plate, four flexural springs and four thermal actuators. The mirror plate has the same thickness as a SOI device layer i.e. 4 µm. The SOI layer is selectively thinned down to 2 µm for fabricating flexural springs and thermal actuators. The thinning of the SOI layer is essential to lower (control) the flexural rigidity of the springs and the actuators and thus to achieve a higher tilt angle at low thermal power. The developed single wafer process is based on dry reactive ion etching CMOS compatible chemistries. The minimum chip size design of 1 mm × 1 mm has a 400 µm diameter mirror plate. Other chip designs include the mirror diameters in the range from 200 to 500 µm. This paper also presents a study on the mirror plate curvature, thermal actuation mechanism and the experimental results. The measured maximum angular deflection achieved was 17 • at an operating applied voltage of less than 2 V, and the radius of curvature of the mirror plate was in the range from 20 to 50 mm. The micromirror was developed for a miniature catheter optical probe for optical coherence tomography in vivo imaging. A low cross-sectional size of the probe and higher resolution are essential for investigating inaccessible pathologies in vivo. This required a compact micromirror chip and yet sufficiently large mirror plate (typically ∼500 µm or more), this trade-off was the key motivation for the research presented in this paper.

A MEMS optical coherence tomography (OCT) probe prototype was developed using a unique assembly based on silicon optical bench (SiOB) methodology. The probe is formed by integrating a three-dimensional (3D) scanning micromirror, gradient refractive index (GRIN) lens and optical fiber on SiOB substrates having prefabricated self-aligned slots. The two-axis scanning micromirror is based on electrothermal actuation with required voltage less than 2 V for mechanical deflections up to 17°. The optical probe was enclosed within a biocompatible, transparent and waterproof polycarbonate tube with a view of in vivo diagnostic applications. The diameter of the miniature probe is less than 4 mm and the length of its rigid part is about 25 mm. The probe engineering and proof of concept of the probe were demonstrated by obtaining en face and three-dimensional OCT images of an IR card used as a standard sample.

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An integrated system of a silicon-based microfabricated polymerase chain reaction (microPCR) chamber and microfabricated electrophoretic glass chips have been developed. The PCR chamber was made of silicon and had aluminum heaters and temperature sensors integrated on the glass anodically bonded cover. Temperature uniformity in the reaction chamber was +/-0.3 degrees C using an improved novel "joint-heating" scheme. Thermal cycling was digitally controlled with a temperature accuracy of +/- 0.2 degrees C. Small operating volumes together with high thermal conductivity of silicon made the device well suited to rapid cycling; 16 s/cycle were demonstrated. For analysis of the PCR products, the chamber output was transferred to the glass microchip by pressure. Analysis time of PCR amplified genomic DNA was obtained in the microchip in less than 180 s. The analysis procedure employed was reproducible, simple and practical by using viscous sieving solutions of hydroxypropylmethylcellulose and dynamically coated microchip channels with poly(vinylpyrrolidone). DNA fragments that differ in size by 18 base pairs (bp) were resolved. Analysis of genomic male and female amplified DNA by microPCR was achieved in microchip, and application of the integrated microPCR-microchip for the identification of bird sex was tested. Genomic DNA samples from several bird species such as pigeon and chicken were analyzed. Hence, the system could be used as well to determine the sex of avian species.

The investigation of structural phase transition and anharmonic behavior of Yb2O3 has been carried out by high-pressure and temperature dependent Raman scattering studies respectively. In situ Raman studies under high pressure were carried out in a diamond anvil cell at room temperature which indicate a structural transition from cubic to hexagonal phase at and above 20.6 GPa. In the decompression cycle, Yb2O3 retained its high pressure phase. We have observed a Stark line in the Raman spectra at 337.5 cm−1 which arises from the electronic transition between 2F5/2 and 2F7/2 multiplates of Yb3+ (4f13) levels. These were followed by temperature dependent Raman studies in the range of 80–440 K, which show an unusual mode hardening with increasing temperature. The hardening of the most dominant mode (Tg + Ag) was analyzed in light of the theory of anharmonic phonon-phonon interaction and thermal expansion of the lattice. Using the mode Grüneisen parameter obtained from high pressure Raman measurements; we have calculated total anharmonicity of the Tg + Ag mode from the temperature dependent Raman data.

In this work, the synthesis, structural and photophysical characterization of six phosphorescent H 2 O-soluble Pt(II) complexes are reported while addressing their emission maxima, photoluminescence quantum yields (Φ L ), lifetimes (τ), aggregation tendency, and microenvironment sensitivity as a function of the substitution pattern on the main tridentate luminophore. Different ancillary ligands, namely, a trisulfonated phosphane and maltohexaose-conjugated pyridines (with or without amide bridges), were introduced and evaluated for the realization of switch-on-photoluminescent labels reporting on the microenvironment sensed in biofilms of Gram + and Gram − models, namely, Staphylococcus aureus and Escherichia coli. With the aid of confocal luminescence micro(spectro)scopy, we observed that selected complexes specifically interact with the biofilms while leaving planktonic cells unlabeled. By using photoluminescence lifetime imaging microscopy, excited-state lifetimes within S. aureus biofilms were measured. The photoluminescence intensities were drastically boosted, and the excited state lifetimes were significantly prolonged upon binding to the viscous biofilm matrix, mainly due to the suppression of radiationless deactivation pathways upon shielding from physical quenching processes, such as interactions with solvent molecules and 3 O 2 . The best performances were attained for non-aggregating complexes with maltohexaose targeting units and without amide bridges. Notably, in the absence of the maltodextrin, a hydrophobic adamantyl moiety suffices to attain a sizeable labeling capacity. Moreover, photoluminescence studies showed that selected complexes can also effectively interact with E. coli biofilms, where the bacterial cells are able to partially uptake the maltodextrin-based agents. In summary, the herein introduced concepts enable the development of specific biofilm reporters providing spatial resolution as well as lifetime-and spectrum-based readouts. Considering that most theragnostic agents reported so far mainly address metabolically active bacteria at the surface of biofilms but without reaching cells deeply immersed in the matrix, a new platform with a clear structure-property correlation is provided for the early detection of such bacterial arrays.

The phase transformation in nano-crystalline dysprosium sesquioxide (Dy 2 O 3 ) under high pressures is investigated using in situ Raman spectroscopy. The material at ambient was found to be cubic in structure using X-ray diffraction (XRD) and Raman spectroscopy, while atomic force microscope (AFM) showed the nano-crystalline nature of the material which was further confirmed using XRD. Under ambient conditions the Raman spectrum showed a predominant cubic phase peak at 374 cm −1 , identified as F g mode. With increase in the applied pressure this band steadily shifts to higher wavenumbers. However, around a pressure of about 14.6 GPa, another broad band is seen to be developing around 530 cm −1 which splits into two distinct peaks as the pressure is further increased. In addition, the cubic phase peak also starts losing intensity significantly, and above a pressure of 17.81 GPa this peak almost completely disappears and is replaced by two strong peaks at about 517 and 553 cm −1 . These peaks have been identified as occurring due to the development of hexagonal phase at the expense of cubic phase. Further increase in pressure up to about 25.5 GPa does not lead to any new peaks apart from slight shifting of the hexagonal phase peaks to higher wavenumbers. With release of the applied pressure, these peaks shift to lower wavenumbers and lose their doublet nature. However, the starting cubic phase is not recovered at total release but rather ends up in monoclinic structure. The factors contributing to this anomalous phase evolution would be discussed in detail.

Pressure and temperature dependent Raman scattering studies on Ho2O3 have been carried out to investigate the structural transition and the anharmonic behavior of the phonons. Ho2O3 undergoes a transition from cubic to monoclinic phase above 15.5 GPa, which is partially reversible on decompression. The anharmonic behavior of the phonon modes of Ho2O3 from 80 K to 440 K has been investigated. We find an anomalous line-width change with temperature. The mode Grüneisen parameter of bulk Ho2O3 was estimated from high pressure Raman investigation up to 29 GPa. Furthermore, the anharmonic components were calculated from the temperature dependent Raman scattering.