Aqueous solutions of alcohols are used in several applications, from pharmaceutics and biology, to chemical, biofuel, and food industries. Nonetheless, development of a simple, inexpensive, and portable sensing device for the quantification of water in water-ethanol mixtures remains a significant challenge. Photonic crystals (PhCs) operating at very high-order photonic bandgaps (PBGs) offer remarkable opportunities for the realization of chemical sensors with high sensitivity and low detection limit. However, high-order PhC structures have been mostly confined to mere theoretical speculations so far, their effective realization requiring microfabrication tools enabling the control of periodic refractive index modulations at the submicrometric scale with extremely high accuracy and precision. Here, we report both experimental and theoretical results on high-sensitivity chemical analysis using vertical, silicon/air 1D-PhCs with spatial period of 10 and 20 mu m (namely, over 10 times the operation wavelength) featuring ultra-high-order PBGs in the near-infrared region (namely, up to 50th at 1.1 mu m). Fabrication of high-order 1D-PhCs was carried out by electrochemical micromachining (ECM) of silicon, which allowed both surface roughness and deviation from vertical of etched structures to be controlled below 5 nm and 0.1%, respectively. Optical characterization of ECM-fabricated 1D-PhCs, which was performed by acquiring reflectivity spectra over the wavelength range 1-1.7 mu m, highlighted the presence of ultra-high-order PBGs with minor optical losses (i.e., <1 dB in reflectivity) separated by deep reflectivity notches with high Q- factors (i.e., >6000), in good agreement with theoretical calculations. Remarkably, the use of high-order 1D-PhCs as refractometric transducers for the quantitative detection of traces of water in water-ethanol mixtures, allowed high sensitivity (namely, either 1000 nm/RIU or similar to 0.4 nm/% of water), good detection limit (namely, 5 x 10(-3) RIU or similar to 10% water), and excellent resolution (namely, either 6 X 10(-4) RIU or 1.6% of water) to be reliably achieved on a detection volume of about 168 fL.

Three-dimensional imaging solutions provide depth perception that cannot be achieved with traditional two-dimensional systems. A 3D optical inspection system can be implemented using structured light as 3D sensing technology. In this paper, we show that structured light can be projected onto the measured object by means of an innovative scanning microsystem that employs a single-axis torsional MEMS mirror for fast steering a near infra-red laser beam on a diffractive silicon microstructure. As a proof of principle of the functionality of the designed microsystem, the generated line patterns are shone on 3D objects and deformation of the projected lines is detected with a CMOS camera. From line deformation, the object depth is calculated and found in accordance to the geometrical size. The developed miniaturized solution overcomes typical drawbacks of other scanning technologies such as large size and heavy weight.

We demonstrate the use of near infra-red low-coherence reflectometry combined with low-cost, rectangular glass micro-capillaries for label-free refractive index sensing of non-homogenous fluids. To test the capability of the proposed method to investigate highly diffusing media, we estimate the average refractive index (RI) of whole milk and Red Blood Cells (RBC) inserted in rectangular glass capillaries with channel depth equal to 100 μm and 50 μm, respectively. Then, as an example of interest, we estimate the RI of hematological and epithelial cells in normal and malignant condition gently confined in capillaries with channel depth and walls thickness equal to 50 μm. The non-contact, remote optical readout was performed by means of a tungsten lamp emitting in the near infrared, thus with minimum invasiveness for biological tissues.

The advances in proteomics and genomics have led to discover a lot of biomarkers that can potentially be used as diagnostic and prognostic indicators of diseases. Simultaneously, a huge research effort has been invested in developing biosensors that could monitor the interaction of biological materials. Such sensors are required to be fast, real time, label free and highly sensitive to the appropriate biomarker. One of the possible solutions is surface plasmon resonance imaging (iSPR) biosensor. Nevertheless, some important milestones still need to be reached for a successful application. Indeed, iSPR instruments commercially available have a poor sensitivity to low biomarker concentration and they are quite expensive. In this paper, we show a compact instrument, called Imaging NanoplasmonicsTM (iNPx), designed to overcome these limits. A nanostructured interface is introduced to increase the sensitivity of different immunoassay reactions and with the use of a very low volume of material. Then, as a proof of principle, we report an example of specific application for the monitoring of the interaction between some variants of FLAG peptides with the monoclonal antibody Anti-FLAG. The proposed platform allows extreme versatility for multiplexed diagnostic and/or food quality applications.

We report the application of an all-fiber setup for spectral reflectivity measurements on rectangular glass microcapillaries, in view of their application as micro-opto-fluidic devices for detection of solution concentration. We tested two kind of capillaries, both with 50 μm × 500 μm cross section but different wall thickness, respectively equal to 35 μm and 50 μm. Optical readout was provided by a broadband light source with λ c = 1.55 μm. We here compare the results obtained on the two different devices in terms of sensitivity and limit of detection when tested with Glucose solutions in water.

In recent years the development of silicon micromachining technologies has required more efforts in research to find non-contact measurement techniques for in-depth, non-destructive inspection of layered and microstructured samples. In this work, we apply a optical low-coherence reflectometry for in-plane and out-of-plane measurements aimed at detecting the optical path between hidden interfaces of several silicon devices with characteristic distance in the range 3 - 17 μm. The implemented configuration is based on a fiberoptic Michelson interferometer and it used infrared broadband radiation in the wavelength range of 1.2 - 1.7 μm, exhibiting a coherence length shorter than 2 μm. Out-of-plane measurements were performed to detect the optical pathlength of the main structural layers of a MEMS gyroscope. Moreover, in-plane measurements on vertical periodic silicon/air microstructures allowed us to detect the optical path among several silicon/air interfaces. Arrays with different spatial period were tested and the optical distance between hidden interfaces was obtained with high in-depth resolution. The results were in good agreement with the design parameters of the specific device. The proposed spot optical technique is a powerful and highly versatile diagnostic tool for non-destructive testing of silicon devices.

The refractive index of cells provides insights into their composition, organization and function. Moreover, a good knowledge of the cell refractive index would allow an improvement of optical cytometric and diagnostic systems. Although interferometric techniques undoubtedly represent a good solution for quantifying optical path variation, obtaining the refractive index of a population of cells non-invasively remains challenging because of the variability in the geometrical thickness of the sample. In this paper, we demonstrate the use of infrared low-coherence reflectometry for non-invasively quantifying the average refractive index of cell populations gently confined in rectangular glass micro-capillaries. A suspension of human red blood cells in plasma is tested as a reference. As a use example, we apply this technique to estimate the average refractive index of cell populations belonging to epithelial and hematological families.

We investigated the capacity of tumour cells to populate the gaps of three-dimensional microstructures (3D-SMS) formed by periodic arrays of parallel 3-μm-thick silicon walls separated by 5-μm-wide, 50 μm-deep air gaps. To evaluate a possible correlation between this feature and cell aggressiveness, we tested eight human tumour cell lines with a well known different aggressive potential. The qualitative analysis performed by fluorescence microscopy revealed that some tumour cell lines populate the narrow gaps of the microstructure due to their greater plasticity and enhanced aggressiveness; on the other hand, cells with low aggressive potential are less prone to colonise the gaps. Image analysis of fluorescence microscopy fields allowed the quantification of the fraction of cells inside the gaps over the total cell number. Our results suggest that tumour cell plasticity could be considered as a biomarker of aggressiveness of tumour cells grown in an innovative 3D micro-device characterised by a well-defined and highly reproducible geometrical layout.

The design and fabrication of nanopores within three-dimensionally structured gold films with spherical microcavities of 1.2 μm diameter and 0.6 μm deep in hexagonal close-packed arrays, are described. The cavities are fabricated by electroplating gold around self-assembled arrays of polymer spheres. Following removal of the spheres, and `lift-off' of the 3D structured gold film, some of the microcavities were milled with a Helium Ion Microscope to provide nanopores through the centre of the microcavity base right through the film. The geometry of the nanopore within the device is designed using theoretical approaches to provide the optimal electric field intensity in the very centre of the nanopore when excited with light of ~ 600 nm (in water). In this paper we report the theoretical simulations used to evaluate the optimal geometry of the nanopore within the centre/base of the gold microcavity. Although a number of various geometries and sizes of pores were considered the theoretical results provide evidence that a pore of 50nm with rounded corners will provide the greatest electrical field intensity inside the pore and the fabrication results provide a demonstrated practical approach for creation of these nanopores within these 3D gold structured films.

The use of patterned light for three-dimensional (3D) imaging and movement tracking has been in the last decade object of experimental investigations for industrial, scientific, and consumer applications. In this paper, we demonstrate the functionality of a compact silicon microsystem for patterned light generation suitable for 3D imaging. It incorporates a single-axis torsional MEMS mirror for steering a near-infrared beam on a diffractive silicon microstructure that projects light patterns on the target. We, here, report images, acquired with a CMOS camera, of the detected light patterns realized with different diffractive elements. As an example of application, we have illuminated 3D objects with a generated line pattern and then detected the deformation of the projected lines with the same camera. By image processing, from the line deformation, we have estimated the object depth that was found in agreement with the geometrical size.

We recently employed three-dimensional (3D) silicon microstructures (SMSs) consisting in arrays of 3 μm-thick silicon walls separated by 50 μm-deep, 5 μm-wide gaps, as microincubators for monitoring the biomechanical properties of tumor cells. They were here applied to investigate the in vitro behavior of HT1080 human fibrosarcoma cells driven to apoptosis by the chemotherapeutic drug Bleomycin. Our results, obtained by fluorescence microscopy, demonstrated that HT1080 cells exhibited a great ability to colonize the narrow gaps. Remarkably, HT1080 cells grown on 3D-SMS, when treated with the DNA damaging agent Bleomycin under conditions leading to apoptosis, tended to shrink, reducing their volume and mimicking the normal behavior of apoptotic cells, and were prone to leave the gaps. Finally, we performed label-free detection of cells adherent to the vertical silicon wall, inside the gap of 3D-SMS, by exploiting optical low coherence reflectometry using infrared, low power radiation. This kind of approach may become a new tool for increasing automation in the drug discovery area. Our results open new perspectives in view of future applications of the 3D-SMS as the core element of a lab-on-a-chip suitable for screening the effect of new molecules potentially able to kill tumor cells.

We report the application of rectangular glass microcapillaries with cross-section of 20 mu m x 200 mu m and 50 mu m x 500 mu m as capillary-driven liquid-core optical cavities for fluid refractive index sensing. Reflected power spectra in two wavelength bands (around 1.3 mu m and 1.55 mu m) are detected with readout broadband radiation crossing the capillary in orthogonal direction with respect to the flat sides. Using a fiberoptic scheme for remote, non-contact measurements and inserting glucose or bovine serum albumin solutions in water at different concentrations as test fluids, we have revealed the shift of the wavelength position of the reflectivity minima due to refractive index variations. The combination of these low-cost devices with a spectral readout method allows achieving sensitivities higher than 250 nm/RIU and limits of detection better than 1.3 x 10(-3) RIU.

Design and fabrication of three-dimensionally structured, gold membranes containing hexagonally close-packed microcavities with nanopores in the base, are described. Our aim is to create a nanoporous structure with localized enhancement of the fluorescence or Raman scattering at, and in the nanopore when excited with light of approximately 600 nm, with a view to provide sensitive detection of biomolecules. A range of geometries of the nanopore integrated into hexagonally close-packed assemblies of gold micro-cavities was first evaluated theoretically. The optimal size and shape of the nanopore in a single microcavity were then considered to provide the highest localized plasmon enhancement (of fluorescence or Raman scattering) at the very center of the nanopore for a bioanalyte traversing through. The optimized design was established to be a 1200 nm diameter cavity of 600 nm depth with a 50 nm square nanopore with rounded corners in the base. A gold 3D-structured membrane containing these sized microcavities with the integrated nanopore was successfully fabricated and 'proof of concept' Raman scattering experiments are described.

In recent years, there is an increasing interest in the demonstration of new optical and instrumental configurations for realizing structured light suitable for 3D surface imaging. This innovative technique has the advantage, with respect to traditional cameras and imaging sensors, to take into account the depth information of the object. In this work, we have investigated the possibility to generate structured light using a single-axis torsional micromirror realized by MEMS technology and diffractive optical elements working in transmission.

In this work, silicon micromachined structures (SMS), consisting of arrays of 3- μm-thick silicon walls separated by 50- μm-deep, 5- μm-wide gaps, were applied to investigate the behavior of eight tumor cell lines, with different origins and biological aggressiveness, in a three-dimensional (3D) microenvironment. Several cell culture experiments were performed on 3D-SMS and cells grown on silicon were stained for fluorescence microscopy analyses. Most of the tumor cell lines recognized in the literature as highly aggressive (OVCAR-5, A375, MDA-MB-231, and RPMI-7951) exhibited a great ability to enter and colonize the narrow deep gaps of the SMS, whereas less aggressive cell lines (OVCAR-3, Capan-1, MCF7, and NCI-H2126) demonstrated less penetration capability and tended to remain on top of the SMS. Quantitative image analyses of several fluorescence microscopy fields of silicon samples were performed for automatic cell recognition and count, in order to quantify the fraction of cells inside the gaps, with respect to the total number of cells in the examined field. Our results show that higher fractions of cells in the gaps are obtained with more aggressive cell lines, thus supporting in a quantitative way the observation that the behavior of tumor cells on the 3D-SMS depends on their aggressiveness level.

With the development of silicon micromachining technologies, non-contact measurement techniques for in-depth non-destructive inspection of layered and microstructured samples are becoming increasingly relevant. In this paper, we apply optical low-coherence reflectometry (OLCR) to detect the optical path between the interfaces of several silicon devices with characteristic distance in the range 3-17 μm. The implemented configuration is based on a fiberoptic Michelson interferometer that exploits infrared broadband radiation in the wavelength range of 1.2-1.7 μm, with coherence length shorter than 2 μm, for performing spot tomographic measurements. OLCR enabled out-of-plane measurements on a MEMS linear accelerometer and in-plane measurements on vertical periodic silicon/air microstructures. The optical distance between hidden interfaces was found well in agreement with the design parameters.

We report the functionality of optical low-coherence reflectometry (OLCR) to characterize glass micro-capillaries with 50-μm deep rectangular cross section, in view of their application as microoptofluidic devices. We exploited infrared radiation generated by a tungsten lamp in a time-domain low-coherence interferometer based on a fiberoptic Michelson scheme. OLCR allowed us to easily detect the optical distance between in-depth interfaces of the capillary as well as the refractive index of ethylene glycol solutions in water at different concentrations, which were inserted into the channel by capillary action.

In this work, we report the characterization of 5-cm-long glass micro-capillaries with 20 μm × 200 μm and 50 μm × 500 μm (nominal values) inner dimensions of the rectangular channel. Optical low-coherence reflectometry enables detection of the optical distance between in-depth interfaces of the glass micro-capillary also in presence of fluids inserted into the channel just by capillary action. Thus, group refractive index of the filling solution can be easily recovered.

Single-axis rotational micromirrors actuated by comb finger structures have been designed in view of their application in reflective scanning picoprojectors for laser beam displacement along two perpendicular directions to obtain a raster scan scheme. A resonant mirror operating at a frequency around 25 kHz, suitable for horizontal scans, as well as a linear mirror, suitable for vertical scan at the typical video refresh rate (60 Hz), have been fabricated by Silicon-on-Insulator technology and are illustrated in this paper. We have in particular exploited the potentialities of semiconductor laser self-mixing interferometry, a powerful technique for characterizing the dynamic response of MEMS, for detecting the electromechanical response of both kinds of micromirrors. We report the results of the spot optical measurements performed on resonant and linear mirrors aimed at detecting the frequency of the fundamental rotational mode as well as of the in-plane and out-of-plane modes, close in frequency to the fundamental mode. We have experimentally demonstrated that the fabricated devices are suitable for high-resolution miniaturized projectors, in terms of frequency response and scanning angle.