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Piezoelectric polymers have been known to exist for more than 40 years, but in recent years they have been recognized as smart materials for the fabrication of microsensors, microactuators and other micro-electro-mechanical systems (MEMS). In this work, femtosecond laser micromachining of a polyvinylidene fluoride (PVDF) film, coated with NiCu on both sides, has been studied to understand selective patterning mechanisms of NiCu layers and ablation characteristics of PVDF films. A detailed characterization of morphological changes of the laser-irradiated areas has been investigated using scanning electron microscopy. Through morphological analysis, the multiple shot damage thresholds of a 28 µm thick PVDF film and 40 nm thick NiCu layer have been determined. Surface morphology examination indicates that NiCu layers are removed from the PVDF film through a sequence of cracking-peeling off-curling. In addition, the NiCu layer on the rear side was also removed by the partially transmitted laser energy. The PVDF film was removed in forms of bundles of filaments and solid fragments by a combination of pure ablation and explosive removal of material by bursting of bubbles; the role of the explosive removal becomes more dominant with the increase of laser fluence. Optimal process conditions for cutting of the PVDF film and patterning of the NiCu coating without damaging the PVDF polymer have been established and applied to fabricate a vibration microsensor prototype that shows significant potential in using PVDF-based functional microdevices for telecommunications, transportation and biomedical applications.

The topography, radial spread, and chemical composition of the slag produced during percussion and trepanning hole drilling techniques using femtosecond laser were investigated. Results of analyses by optical microscopy, scanning electron microscopy, and energy dispersion spectroscopy are presented. While there were no significant differences in the average ablation rates observed when a near infrared femtosecond laser was used, when compared with the ultraviolet nanosecond laser ablation of alumina (Al 2 O 3 ) ceramics, that of the femtosecond laser provided much cleaner holes. There was an absence of particulates due to re-solidification of molten material around the periphery of the hole. The slag consisted of ultrafine powders formed during condensation of the supersaturated ablation plume. This slag can easily be removed in an ultrasonic bath with a mixture of acetone and water. In combination with trepanning hole drilling, the femtosecond laser produced micro-via holes, in alumina wafers, that were free of cracks and re-cast molten material.

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