Fabrication and characterization of AlN-based flexible piezoelectric pressure sensor integrated into an implantable artificial pancreas.

This study reports on the fabrication and characterization of an event detection subsystem composed of a flexible piezoelectric pressure sensor and the electronic interface to be integrated into an implantable artificial pancreas (IAP) for diabetic patients. The developed sensor is made of an AlN layer, sandwiched between two Ti electrodes, sputtered on Kapton substrate, with a preferential orientation along c-axis which guarantees the best piezoelectric response. The IAP is made of an intestinal wall-interfaced refilling module, able to dock an ingestible insulin capsule. A linearly actuated needle punches the duodenum tissue and then the PDMS capsule to transfer the insulin to an implanted reservoir. The device is located at the connection of the needle with the linear actuator to reliably detect the occurred punching of the insulin-filled capsule. Finite Element Analysis (FEA) simulations were performed to evaluate the piezoelectric charge generated for increasing loads in the range of interest, applied on both the sensor full-area and footprint area of the Hamilton needle used for the capsule punching. The sensor-interface circuit was simulated to estimate the output voltage that can be obtained in real operating conditions. The characterization results confirmed a high device sensitivity during the punching, in the low forces (0-4 N) and low actuator speed (2-3 mm/s) ranges of interest, meeting the requirement of the research objective. The choice of a piezoelectric pressure sensor is particularly strategic in the medical field due to the request of self-powered implantable devices which do not need any external power source to output a signal and harvest energy from natural sources around the patient.

Fe3O4/γ-Fe2O3 nanoparticle multilayers deposited by the Langmuir-Blodgett technique for gas sensors application.

Fe3O4/γ-Fe2O3 nanoparticles (NPs) based thin films were used as active layers in solid state resistive chemical sensors. NPs were synthesized by high temperature solution phase reaction. Sensing NP monolayers (ML) were deposited by Langmuir-Blodgett (LB) techniques onto chemoresistive transduction platforms. The sensing ML were UV treated to remove NP insulating capping. Sensors surface was characterized by scanning electron microscopy (SEM). Systematic gas sensing tests in controlled atmosphere were carried out toward NO2, CO, and acetone at different concentrations and working temperatures of the sensing layers. The best sensing performance results were obtained for sensors with higher NPs coverage (10 ML), mainly for NO2 gas showing interesting selectivity toward nitrogen oxides. Electrical properties and conduction mechanisms are discussed.

Antibacterial coatings on haemodialysis catheters by photochemical deposition of silver nanoparticles.

Antibacterial coatings on catheters for acute dialysis were obtained by an innovative and patented silver deposition technique based on the photo-reduction of the silver solution on the surface of catheter, with consequent formation of antibacterial silver nanoparticles. Aim of this work is the structural and morphological characterization of these medical devices in order to analyze the distribution and the size of clusters on the polymeric surface, and to verify the antibacterial capability of the devices treated by this technique against bacterial proliferation. The structure and morphology of the silver nanoparticles were investigated by using scanning and transmission electron microscopy. The antimicrobial capability of the catheters after silver deposition was confirmed by antibacterial tests with Escherichia coli. Both scanning electron microscopy analysis and antibacterial tests were performed also after washing catheters for 30 days in deionized water at 37°C, relating these data to thermogravimetric analysis and to energy dispersive spectroscopy, in order to check the resistance of coating and its antimicrobial capability after the maximum time of life of these devices.

The effects of the focus ion beam milling process on the optical properties of semiconductor nanostructures.

In this work, the effects of the focus ion beam (FIB) milling process on the optical properties of semiconductor nanostructures were investigated. With this aim, a sensitive materials system based on InGaAs/GaAs quantum dots with well known and excellent optical properties was selected for the FIB treatment. The FIB technique was used to locally remove a metallic mask deposited on top of the quantum dot sample. The photoluminescence (PL) signal, collected from the circular openings, was used to infer the possible damage effects of the ion beam on the properties of the dots.

Critical issues in the focused ion beam patterning of nanometric hole matrixes on GaAs based semiconducting devices.

This work investigates the critical issues in the focused ion beam (FIB) nanopatterning of semiconducting devices. Matrixes of holes with diameter of about 150 nm were drilled by FIB on the topmost layers of a quantum dot based device. In order to study the presence of artefacts in the active region of the device, the milling parameters were investigated. A careful analysis of the ion beam effects on the structural and morphological features of the holes, mainly due to the heterogeneous composition of the layers to be milled, demonstrated that important deviations from the expected structures, in terms of size, shape and geometry of the holes, as well as layer amorphization and damage, occur.

Sleep disordered breathing in patients with chronic obstructive pulmonary disease.

Sleep has effects on breathing, including changes in respiratory control, airways resistance and muscular contractility. These sleep-related modifications in the respiratory system do not induce adverse effects in healthy subjects, but may cause problems in patients with chronic obstructive pulmonary disease (COPD). Hypo-ventilation causes the most important gas-exchange alteration during sleep in COPD patients, leading to hypercapnia and hypoxemia, especially during rapid-eye-movement (REM) sleep. Blood gases alterations lead to increased arousals, sleep disruption, pulmonary hypertension and higher mortality. The presence of other sleep-related breathing disorders, like sleep apnea syndrome, may induce a more pronounced impairment of gas exchange, both during sleep and wakefulness, and development of symptoms like excessive daytime somnolence. Nocturnal oximetry is recommended to evaluate gas exchange during sleep in COPD patients. Sleep studies are usually indicated when there is a possibility of sleep apnea or obesity-hypoventilation syndrome. The role of non-invasive mechanical ventilation in managing COPD patients with nocturnal hypoventilation is discussed.

Nebulized tobramycin in patients with chronic respiratory infections during clinical evolution of Wegener's granulomatosis.

Aminoglycosides are effective against Pseudomonas aeruginosa but with intravenous administration there are only very low concentrations achieved in sputum; therefore in order to obtain therapeutic levels in patients with endobronchial infections should be administered high doses with increased likelihood to produce both nephrotoxic and ototoxic effects. Direct aerosol delivery of aminoglycosides to the lower respiratory tract has the advantage to achieve high antibiotic sputum concentrations in the infected area with reduced risk of systemic toxic reactions because of minimal absorption into the circulation. Nowadays, except for patients suffering from cystic fibrosis and bronchiectasis, the administration of antibiotics through inhalers is not very much in use. The aim of this study was to administer nebulized tobramycin in chronic respiratory infections developed during the evolution of Wegener's Granulomatosis in order to obtain data concerning the safety and efficacy of inhaled aminoglycosides. The results obtained underlined an improvement in FEV1, FEF75 and PaO2. The aerosolized tobramycin administered in 300 mg doses three times per day for four weeks, showed itself to be effective and safe, not causing any undesirable clinical or microbiological side-effects. Moreover, a long term treatment has been shown to control the Pseudomonas aeruginosa infection on the bronchial system in Wegener's granulomatosis and reduce the frequency of exacerbations in chronic patients.

Correlation between shape and electronic states in nanostructures

We show how the electronic states of quantum wires and quantum dots can be evaluated exactly starting from the profile of the nanostructure observed by transmission electron microscopy, scanning tunneling microscopy and atomic force microscopy. The calculated quantization energies reproduce the energy position of the luminescence resonances in the optical spectra of different samples, without fitting parameters.