Fibre-top atomic force microscope probe with optical near-field detection capabilities.

We present a fibre-top probe fabricated by carving a tipped cantilever on an optical fibre, with the tip machined in correspondence of the fibre core. When approached to an optical prism illuminated under total internal reflection conditions, the tip of the cantilever detects the optical tunnelling signal, while the light coupled from the opposite end of the fibre measures the deflection of the cantilever. Our results suggest that fibre-top technology can be used for the development of a new generation of hybrid probes that can combine atomic force microscopy with scanning near field optical microscopy.

Scanning probe nanoimprint lithography.

The present paper reports on a novel lithographic approach at the nanoscale level, which is based on scanning probe microscopy (SPM) and nanoimprint lithography (NIL). The experimental set-up consists of an atomic force microscope (AFM) operated via software specifically developed for the purpose. In particular, this software allows one to apply a predefined external load for a given lapse of time while monitoring in real-time the relative distance between the tip and the sample as well as the normal and lateral force during the embossing process. Additionally, we have employed AFM tips sculptured by means of focused ion beam in order to create indenting tools of the desired shape. Anti-sticking layers can also be used to functionalize the tips if one needs to investigate the effects of different treatments on the indentation and de-molding processes. The lithographic capabilities of this set-up are demonstrated on a polystyrene NIL-patterned sample, where imprinted features have been obtained upon using different normal load values for increasing time intervals, and on a thermoplastic polymer film, where the imprint process has been monitored in real-time.

Scanning force images through the 'Milliscope'--a probe microscope with very wide scan range.

The effectiveness and adequacy of a home-built scanning force microscope (SFM) able to cover a volume of approximately 1.2 x 1.2 x 0.13 mm(3) (X x Y x Z) were tested on calibrating objects, as well as on cytological and histological samples. The instrument was designed for matching the magnification range of an optical microscope (approximately 20-1200x) but its dynamics were one or two orders of magnitude higher, thanks to a lateral resolution of about 10 nm. Images ranging in size from 1.2 x 1.2 mm(2) to 1 x 1 microm(2) showed a quality comparable to that given by other SFMs on similar materials. The 'Milliscope' is a curious but effective imaging tool whose operating range overlaps at one extreme with a goldsmith's eyepiece, and at the other with an electron microscope. The intrinsic limits of scanning probe techniques and of the available SFM cantilevers prevented us taking complete advantage of the wide height range of our scanner. However, our results show that an instrument having a very wide scan area, obtained through simple, inexpensive and intrinsically linear techniques, can give a good performance even at small scan sizes. This encourages us to develop wide scan instruments, which could further increase the already extensive use of scanning force microscopy in biology.

Simultaneous micromechanical and electromagnetic detection of electron paramagnetic resonance

The peculiar advantages of simultaneous observation by electromagnetic and micromechanical methods in EPR spectroscopy are discussed. The development of a novel apparatus with the capability of this simultaneous detection is described. Experiments at 23 GHz show the performance of the apparatus. The problems related to the sensitivity and to the spatial resolution are analyzed. Future prospects are presented. Copyright 1999 Academic Press.

The torsional properties of single selected osteons.

The aim of the present investigation is to determine the mechanical behavior of single selected osteons loaded by torsion along their axis. Two osteon types were chosen: (a) fully calcified 'longitudinal' osteons, whose fibers (and, consequently, crystallites) have a marked longitudinal spiral course in successive lamellae, (b) fully calcified 'alternate' osteons, whose fibers (and, consequently, crystallites) have a marked longitudinal spiral course in one lamella, and an apparently transverse or circular course in the next. The osteon samples, which were cylindrically shaped, and whose extremities fitted into two rectangular lugs, were prepared on a microturning lathe. The principle of the specially manufactured torsional device was that of a pendulum set oscillating around a very sharp wedge so as to reduce friction to negligible levels. The results indicate that longitudinal osteons are those most resistant to torsional loading. The low resistance to torsional loading of the lamellae whose fibers apparently have an almost transversal course is discussed with reference to recent views on the microstructure of this type of lamella.

The bending properties of single osteons.

The bending properties of two fully calcified osteon types (longitudinal and alternate) have been investigated in 62 cylindrical samples by applying the technique of three-point bending loading. The bending of each sample was recorded using a microwave micrometer based on the cavity and pulse technique. It has been shown that alternate osteons are better able to withstand bending stress than longitudinal ones. This result offers a definitive explanation for the high concentration of transverse lamellae in pathologically bowed bone shaft.