Stitchless support-free 3D printing of free-form micromechanical structures with feature size on-demand

Femtosecond laser based 3D nanolithography is a powerful tool for fabricating various functional micro- and nano-objects. In this work we present several advances needed to push it from the laboratory level use to the industrial production lines. First, linear stage and galvo-scanners synchronization is employed to produce stitch-free mm-sized structures. Furthermore, it is shown that by varying objective numerical apertures (NA) from 1.4 NA to 0.45 NA, voxel size can be tuned in the range from sub μm to tens of mm, resulting in structuring rates between 1809 μm3/s and 313312 μm3/s at 1 cm/s translation velocity achieved via simultaneous movement of linear stages and scanners. Discovered voxel/throughput scaling peculiarities show good agreement to ones acquired with numerical modeling. Furthermore, support-free 3D printing of complex structures is demonstrated. It is achieved by choosing pre-polymer that is in hard gel form during laser writing and acts as a dissolvable support during manufacturing. All of this is combined to fabricate micromechanical structures. First, 1:40 aspect ratio cantilever and 1.5 mm diameter single-helix spring capable of sustaining extreme deformations for prolonged movement times (up to 10000 deformation cycles) are shown. Then, free-movable highly articulated intertwined micromechanical spider and squids (overall size up to 10 mm) are printed and their movement is tested. The presented results are discussed in the broader sense, touching on the stitching/throughput dilemma and comparing it to the standard microstereolithography. It is shown where multiphoton polymerization can outpace standard stereolithography in terms of throughput while still maintaining superior resolution and higher degree of freedom in terms of printable geometries.

Modal Analysis of a MEMS Cantilever

Micro-Electro-Mechanical Systems (MEMS), also known as micromechatronic devices, integrate on the same chip (substrate) both micromechanical structures and microelectronics components. Microcantilevers are miniaturized beams clamped at one end and with the other end suspended freely outwards. They can be used as resonant structures in nano/micro mass detectors, allowing a quantitative assessment of the (substance) mass attached to these devices. An accurate modal analysis makes possible to estimate the sensitivity of the cantilevers or their ability to detect minimum frequencies shifts induced by the substance absorption. In order to obtain a high sensitivity, the structures must present high resonant frequencies (usually bending or torsion), in close correlation with a small equivalent mass. This paper deals with the vibration testing, modeling and simulation of a silicon rectangular microcantilever, micromachined through MEMS technologies. The results of analytical calculations and numerical computation by finite element analysis (FEM) have been compared with those measured through Laser Doppler Vibrometry (LDV) method using MSA-500 system from Polytec.