A Statically Balanced Compliant Ortho-Planar Mechanism for Low-Frequency Energy Harvesting

The usually high eigenfrequencies of miniaturized oscillators can be significantly lowered by reducing the stiffness through static balancing. In this work, a mechanical design for a statically balanced compliant ortho-planar mechanism is proposed. The mechanism was prototyped using laser micro-machining and subsequently preloaded through packaging. The statically balanced property of the mechanism was experimentally validated by a measurement of the force-deflection relation. A piezoelectric transducer was added and the resulting energy harvesting device was tested at low-frequency vibration of 2Hz. Compared to a reference device, an almost sixfold increase in performance was observed due to the static balancing. Therefore, it was found that the use of static balancing can improve the power output of piezoelectric energy harvesters for low-frequency vibrations.

Laser Micro Machining Using a Photonic Nanojet in Water Medium

A photonic nanojet (PNJ) is a fine and high intensity light beam that is generated from a dielectric microsphere irradiated by a laser. A PNJ has a smaller beam diameter than the wavelength of the incident laser and can propagate for longer than 1 μm with high intensity and minimal divergence. In other words, a PNJ has a long depth of focus. Due to its outstanding optical properties, a PNJ is suitable for laser micro machining to create sub-micrometer scale structures. Depth of focus of a PNJ generated in water is longer than in air. In this paper, we experimentally investigated machining characteristics of laser micro machining using a PNJ in water medium. First, electromagnetic simulation was conducted to know the intensity distribution of PNJ in water medium. The simulation demonstrated that PNJ in water mdium has beam diameter of sub-micrometer scale and micrometer scale depth of focus. Next, machining experiments were also conducted on a silicon substrate. A femtosecond laser was used as the machining laser. By controlling the microsphere position, the PNJ position can be controlled in the propagation direction. Sub-micrometer scale hole diameters were obtained even when the PNJ position in the propagation direction was changed by 3 μm. In conclusion, the long depth of focus of a photonic nanojet in water medium enable to create sub-micrometer scale structures.

Generation of Surfaces with Isotropic and Anisotropic Wetting Properties by Curved Water Jet Guided Laser Micro-Machining

This experimental work utilizes a newly developed method, curved water jet guided laser micro-machining, to generate micro features on metallic surfaces. During the process, material is removed by a high-power nanosecond laser beam which is transmitted through a high-pressure micro water jet via total internal reflection. To achieve intricate texturing patterns, a secondary motion component is superimposed on the XY motion of the workpiece provided by the motion stage. The secondary motion is generated by deflecting the water jet trajectory by a controllable dielectrophoretic force. The induced secondary motion of the water jet cuts the processing time to one half when generating texture patterns for isotropic wetting as compared to processes with only XY motion. The ability to alter the water jet's trajectory by tens of microns at high frequencies, which is beyond the capability of conventional CNC machines, allows a wide range of different micro patterns to be generated, profoundly increasing the flexibility and efficiency of the process as compared to conventional approaches. As a demonstration, surface textures for isotropic and anisotropic behaviors are generated on stainless steel surfaces. The influence of feature spacing, motion speed (frequency) and texturing patterns on surface wettability are studied.

Sub-Micrometer Scale Laser Machining Using Position Controlled Photonic Nanojet

A photonic nanojet (PNJ) is a fine and high intensity light beam that is generated from a dielectric microsphere irradiated by a laser. A PNJ has a smaller beam diameter than the wavelength of the incident laser and can propagate for longer than 1 μm with high intensity and minimal divergence. In other words, a PNJ has a long depth of focus. Due to its outstanding optical properties, PNJ is suitable for laser micro machining. In this paper, we theoretically and experimentally investigated machining characteristics of laser micro machining using a PNJ. First, electromagnetic simulations were conducted to estimate hole diameter when PNJ is irradiated to a sample by changing a distance from the microsphere to the sample. The simulation demonstrated that sub-micrometer scale hole diameter could be obtained even when PNJ is defocused by 1 μm due to the long depth of focus. Next, machining experiments were also conducted on a silicon substrate. A femtosecond laser was used as the machining laser. By holding the microsphere with a micropipette and controlling its position, the position of the PNJ can be controlled in the z direction. Micrometer and sub-micrometer scale hole diameters were obtained even when the position of PNJ in the z direction was changed by 1 μm. The hole diameters obtained in the experiment were consistent with the hole diameter estimated by the simulation. In conclusion, the long depth of focus of a photonic nanojet enable to create sub-micrometer scale structure.

Generation of Surfaces With Isotropic and Anisotropic Wetting Properties by Curved Water Jet Guided Laser Micro-Machining

This experimental work utilizes a newly developed method, curved water jet guided laser micro-machining, to generate micro features on metallic surfaces. During the process, material is removed by a high-power nanosecond laser beam which is transmitted through a high-pressure micro water jet via total internal reflection. To achieve intricate texturing patterns, a secondary motion component is superimposed on the XY motion of the workpiece provided by the motion stage. The secondary motion is generated by deflecting the water jet trajectory by a controllable dielectrophoretic force. The induced secondary motion of the water jet cuts the processing time to one half when generating texture patterns for isotropic wetting as compared to processes with only XY motion. The ability to alter the water jet’s trajectory by tens of microns at high frequencies, which is beyond the capability of conventional CNC machines, allows a wide range of different micro patterns to be generated, profoundly increasing the flexibility and efficiency of the process as compared to conventional approaches. As a demonstration, surface textures for isotropic and anisotropic behaviors are generated on stainless steel surfaces. The influence of feature spacing, motion speed (frequency) and texturing patterns on surface wettability are studied.