Two-photon absorption polymerization (2PP) is a versatile lithographic method for building three-dimensional microdevices with sub-diffraction resolution and tunable elasticity. Using 2PP of organo-ceramic hybrid OrmoComp (trimethylolpropane triacrylate), we prepared microsized polymeric cantilevers consisting of the surface-anchored micropillar, long elastic neck and spherical head. A typical microcantilever has the length of 30 micrometers and thickness of 1-2 micrometers. To investigate the mechanical properties of our elastic microcantilever, we applied a laser optical trapping force on the head of the cantilever and bent the head from its equilibrium position. After switching off the laser trap, the head returns to the equilibrium position. The time-dependent restoring trajectory of the head was recorded by a fast video-tracking technique (500 fps) and subjected to the custom-made drift-correcting image analysis. We find that the microcantilever relaxation process is well-described by a single-exponential relaxation curve with a time constant of 16.5 ± 1.2 ms. Assuming a highly overdamped regime, theoretical calculations yielded an apparent Young´s modulus for our OrmoComp microstructure of 1 MPa, which is 3-orders of magnitude smaller than the reported value for the bulk material (~1 GPa). The possible reasons for such discrepancy are discussed.
Elastic micro-cantilever of 30-micrometer size is repeatedly deflected/released by optical tweezers trap, recorded by a high-speed camera (500 frames/sec) and subsequently processed off-line. This paper evaluates the position detection methods of the cantilever head, which is distorted by a diffraction pattern. We developed and tested four methods in our VideoAnalyser software - radial extremes, Hough transform, local corner tracking, and voting normal lines. The time dependence of the head position contains the information about the properties of both: cantilever material and the surrounding environment. Averaging of aligned graphs corresponding to individual cycles significantly improves the signal-to-noise ratio.
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