We review our recent results towards the development of a turnkey 3D laser printer, based on self-Q-switched microchip Nd:YAG lasers, with reproducible sub-100nm resolution, and with large-scale (cm) and fast-speed (cm/sec) capability at micron resolution. First of all, we report on line fabrication with 70nm lateral, and 150nm longitudinal resolutions without significant shrinking. This is due to the tight focusing with green visible wavelength, large numerical aperture, and excellent resin properties. Secondly, we report on two-photon sensitive photoacid generators that lead to efficient 3D microfabrication with epoxy SU-8 resin. Thirdly, we demonstrate high-speed microfabrication of large scale, millimeter size, scaffolds and cemtimeter height needle with high repetition rate (130Khz), and high average power (1W) amplified microchip laser. Finally we demonstrate the two-photon induced cross-linking of antibodies to determine the type of red blood cells in microfluidic channels.
NiTi endodontic rotary instruments subjected to alternating tension and compression stress in root canals may
fracture without prior warning. Once broken, extracting the fractured part from the canal is a difficult job and is
annoying to both the patient and the dentist. Warning of an imminent fracture during clinical use will be a great help to
avoid medical and legal complications. A monitoring system employing Fiber Bragg Grating (FBG) sensors has been
attempted. The reason of using FBG is its small size which is very promising in integrating with the handpiece of the
endodontic equipment. When cracking developed in an rotary instrument, we expect the natural vibration frequency of
the instrument changes. If we can pick up the stress wave transmitted through the structural components of the rotary
instruments, we may be able to detect the occurrence of a crack. In the current work, we found that we can successfully
locate the operation period in the time domain by picking up and analyzing the sound wave using FBG. Furthermore, by
employing Fast Fourier Transform (FFT) on the signal, we can reveal the energy variation and the frequency shifting
phenomenon in specific section of frequency domain. For some characteristic frequencies, it was found that the energy
and frequency varied in a well-defined pattern during the period of crack growth. It is hoped that with these information,
the fatigue failure of rotary instruments can be closely monitored to avoid/alleviate the occurrence of unexpected fracture
during clinical use.