Biomedical subjects

Stefano Cabrini

Publications and source records attributed to Stefano Cabrini.

4 recordsLinked to original sources

PubMed2006

Manganese-induced growth of GaAs nanowires.

GaAs nanowires have been grown on SiO2 and GaAs by molecular beam epitaxy using manganese as growth catalyst. Transmission electron microscopy shows that the wires have a wurtzite-type lattice and that alpha-Mn particles are found at the free end of the wires. X-ray absorption fine structure measurements reveal the presence of a significant fraction of Mn-As bonds, suggesting Mn diffusion and incorporation during wire growth. Transport measurements indicate that the wires are p-type, as expected from doping of GaAs with Mn.

Arsenicals↗

PubMed2005

High resolution printing of DNA feature on poly(methyl methacrylate) substrates using supramolecular nano-stamping.

In recent years, a large number of devices based on organic and biological materials have been developed. To scale-up the production of these systems to industrially acceptable standards, there is a need to develop soft-material stamping approaches with the needed resolution, complexity, and versatility. We have recently developed a DNA-based stamping method (supramolecular nano-stamping, SuNS) that has superior resolution and can print multiple molecules at the same time. A similar technique was independently developed by Crooks and co-workers. Here we show that SuNS can be used to efficiently print DNA features on a polymeric substrate (poly(methyl methacrylate), PMMA) with a 40 nm point resolution and a coverage that exceeds 100 mum2. The stamped PMMA substrate was also used as a master to print on a gold substrate. With PMMA being optically clear and electrically insulating, future applications of SuNS to print DNA micro- and nanoarrays are envisioned.

DNA, Single-Stranded↗

PubMed2004

Microscopy of biological sample through advanced diffractive optics from visible to X-ray wavelength regime.

The aim of this report is to demonstrate a unified version of microscopy through the use of advanced diffractive optics. The unified scheme derives from the technical possibility of realizing front wave engineering in a wide range of electromagnetic spectrum. The unified treatment is realized through the design and nanofabrication of phase diffractive elements (PDE) through which wave front beam shaping is obtained. In particular, we will show applications, by using biological samples, ranging from micromanipulation using optical tweezers to X-ray differential interference contrast (DIC) microscopy combined with X-ray fluorescence. We report some details on the design and physical implementation of diffractive elements that besides focusing also perform other optical functions: beam splitting, beam intensity, and phase redistribution or mode conversion. Laser beam splitting is used for multiple trapping and independent manipulation of micro-beads surrounding a cell as an array of tweezers and for arraying and sorting microscopic size biological samples. Another application is the Gauss to Laguerre-Gauss mode conversion, which allows for trapping and transfering orbital angular momentum of light to micro-particles immersed in a fluid. These experiments are performed in an inverted optical microscope coupled with an infrared laser beam and a spatial light modulator for diffractive optics implementation. High-resolution optics, fabricated by means of e-beam lithography, are demonstrated to control the intensity and the phase of the sheared beams in x-ray DIC microscopy. DIC experiments with phase objects reveal a dramatic increase in image contrast compared to bright-field x-ray microscopy. Besides the topographic information, fluorescence allows detection of certain chemical elements (Cl, P, Sc, K) in the same setup, by changing the photon energy of the x-ray beam.

Escherichia coli↗

PubMed2002

Differential interference contrast x-ray microscopy with twin zone plates.

X-ray imaging in differential interference contrast (DIC) with submicrometer optical resolution was performed by using a twin zone plate (TZP) setup generating focal spots closely spaced within the TZP spatial resolution of 160 nm. Optical path differences introduced by the sample are recorded by a CCD camera in a standard full-field imaging and by an aperture photodiode in a standard scanning transmission x-ray microscope. Applying this x-ray DIC technique, we demonstrate for both the full-field imaging and scanning x-ray microscope methods a drastic increase in image contrast (approximately 20x) for a low-absorbing specimen, similar to the Nomarski DIC method for visible-light microscopy.

Journal Article↗