A Multitouch screen is an obvious choice for a holographic optical tweezers interface, allowing multiple optical traps to be
controlled in real-time. In this paper we describe the user interface used for our original multitouch system and demonstrate
that, for the user tasks performed, the multitouch performs better than a simple point-and-click interface.
Structure and morphology of porphyrin aggregates and influence of temperature, microwave and ultraviolet radiation, and acoustic cavitation on aggregation process were investigated using absorption spectroscopy and atomic force microscopy. In ambient conditions TPPS4 forms stick-like J-aggregates with length of 0.05-3 μm, width 22-50 nm and height 4-5 nm. Increased temperature or MW and UV radiation does not influence the aggregates. Acoustic cavitation leads to destruction of stick-shaped aggregates and activates the formation of larger molecular complexes.
A new technique has been developed to probe the surface microtopography an the viscoelastic properties with the nanometric resolution using the vibrating modes of Scanning Probe Microscopy. Weak cantilevers, although having good force sensitivity, have found limited use for investigating of material's nanomechanical properties by conventional force modulation and intermittent contact atomic force microscopy. This is due to low forces and indentations that these cantilevers are able to exert on the surface and high amplitudes needed to overcome adhesion to the surface. Here it is shown that by employing electrostatic forcing of cantilever the imaging of local elastic properties of surface and subsurface layers can be carried out. Also, by mechanically exciting the higher vibration modes in contact or intermittent contact with the surface and monitoring the phase of vibrations, the contrast due to local surface elasticity together with surface microtopography is obtained.
Simple Matlab/Simulink model is presented allowing to simulate numerically the dynamics of surface coupled cantilever in wide frequency range. Contact interaction between surface and cantilever is estimated by nonlinear distance function. Simulations show that cantilever can retain the harmonic response to the sine excitation above its fundamental resonant frequency due to its small mass and spring constant and strong surface adhesion forces. The motion of the cantilever becomes chaotic at certain combinations of amplitude and frequency of excitation, as cantilever and surface lose contact. Frequency spectrum of cantilever deflection contains high frequency component corresponding to the nonlinear surface-cantilever contact spring and dependent on the surface material parameters.
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