Biomedical subjects

F Formanek

Publications and source records attributed to F Formanek.

4 recordsLinked to original sources

PubMed2006

Investigation of dyed human hair fibres using apertureless near-field scanning optical microscopy.

We present the first studies of dyed human hair fibres performed with an apertureless scanning near-field optical microscope. Samples consisted of 5-microm-thick cross-sections, the hair fibres being bleached and then dyed before being cut. Hair dyed with two molecular probes diffusing deep inside the fibre or mainly spreading at its periphery were investigated at a wavelength of 655 nm. An optical resolution of about 50 nm was achieved, well below the diffraction limit; the images exhibited different optical contrasts in the cuticle region, depending on the nature of the dye. Our results suggest that the dye that remains confined at the hair periphery is mainly located at its surface and in the endocuticle.

Hair↗

PubMed2005

Analysis of the measured signals in apertureless near-field optical microscopy.

We present an analytical model able to explain the optical signal recorded during our experimental approach curves in the infrared at a wavelength lambda=10.6 microm, with a home-made apertureless near-field scanning optical microscope ANSOM. This model uses classical electrodynamics to calculate the scattering cross section of the oscillating tip, considered as a dipole, and its dielectric image in the sample as a function of the tip-sample separation from the near-field to the far-field regime. The dipoles are placed in a non-uniform electric field because of the standing wave arising from the interference between the incident and the specular laser beams. We also added a background field coming from a scatterer on the surface in order to account for zeroing of the optical signal for particular tip-sample separation and interference patterns.

Journal Article↗

PubMed2004

Apertureless scanning near-field fluorescence microscopy in liquids.

We show that apertureless scanning near-field optical microscopes that use sharp vibrating conical tips can be operated in liquid environments. We have investigated the damping of the tip oscillation as a function of its shape and as a function of its depth under the liquid surface. The degradation of the quality factor from 150 in air down to 15 in liquid does not impede to perform topographic and optical measurements with a very good sensitivity. As an example of application, we present near-field fluorescence images of dye-doped polystyrene spheres immersed in a liquid.

Microscopy, Fluorescence↗

PubMedDate not supplied

Apertureless near-field scanning optical microscope working with or without laser source.

An apertureless near-field scanning optical microscope (ANSOM), used indifferent configurations, is presented. Our versatile home-made setup, based on a sharp tungsten tip glued onto a quartz tuning fork and working in tapping mode, allows to perform imaging over a broad spectral range. We have recorded optical images in the visible (wavelength, lambda = 655 nm) and in the infrared (lambda = 10.6 microm), proving that the setup routinely achieves an optical resolution of <50 nm regardless of the illumination wavelength. We have also shown optical images recorded in the visible (lambda = 655 nm) in an inverted configuration where the tip does not perturb the focused spot of the illumination laser. Approach curves as well as image profiles have revealed that on demodulating the optical signal at higher harmonics, we can obtain an effective probe sharpening which results in an improvement of the resolution. Finally, we have presented optical images recorded in the infrared without any illumination, that is, the usual laser source is replaced by a simple heating of the sample. This has shown that the ANSOM can be used as a near-field thermal optical microscope (NTOM) to probe the near field generated by the thermal emission of the sample.

Journal Article↗