Bulk micromachined energy harvesters employing (K, Na)NbO₃thin film

Abstract

In this paper, a micromachined energy harvester employing a lead-free (K, Na)NbO3 (KNN) thin film was reported. KNN is one of the lead-free piezoelectric materials. It is a promising alternative to Pb(Zr, Ti)O3 (PZT). In a micromachined energy harvester, a 2 µm thick KNN film was deposited on a silicon cantilever integrated with a proof mass. The energy harvester achieved an output power of 731 nW and a normalized power density (NPD) of 2.29 μW (g−2 mm−3) at the resonant frequency of 1509 Hz with the acceleration of 10 m s−2. The harvested energy was enhanced considerably by applying bulk micromachining, and was comparable to the PZT-based energy harvesters.

Micro-Energy Harvesters Integrated with a Quatrefoil-Shaped Proof Mass Suspended by Multiple (K,Na)NbO3Beams

“…In this step, we utilized a combination of fast atomic beam etching (FAB) using SF 6 gas and reactive ion etching (RIE) using CHF 3 /Ar gas to etch KNN film. 19,22) This method enabled us to achieve precise patterns, a smooth etching surface, and high selectivity of KNN against the Pt film. KNN properties.…”

“…The power generation from a sputtered KNN film has already been reported. 18,19) However, a practical application of the KNN film to the micromachined structure has not been adequately reported. [18][19][20] In this study, a fully micromachined energy harvester employing the KNN film and nonlinear feature of the clamped-clamped beam was fabricated and evaluated.…”

Interdependence of piezoelectric coefficient and film thickness in LiTaO3 cantilevers

“…Efficient energy harvesting can be realized by integrating piezoelectric materials in different geometries, using different methods. For example, a circular diaphragm array, 22 piezo fiber composites, 23 low‐frequency piezo QuickPack, 24 three‐axis energy harvester, 25 bistable energy harvesters with a synchronized switch harvester on inductor (SSHI) circuit, 26 and bulk micromachined energy harvesters 27 . However, applying current fabrication techniques, Microelectromechanical systems (MEMS)‐based techniques often require complex multi‐step processing, which leads to the manufacturing cost remains high 28 .…”

“…For example, a circular diaphragm array, 22 piezo fiber composites, 23 low-frequency piezo QuickPack, 24 three-axis energy harvester, 25 bistable energy harvesters with a synchronized switch harvester on inductor (SSHI) circuit, 26 and bulk micromachined energy harvesters. 27 However, applying current fabrication techniques, Microelectromechanical systems (MEMS)-based techniques often require complex multi-step processing, which leads to the manufacturing cost remains high. 28 LiTaO 3 -based devices could be an ideal choice for energy harvesting in a high-temperature environment (<723°C).…”

A High Performance Piezoelectric Micro Energy Harvester Based on Stainless Steel Substrates

“…The performance of the piezoelectric materials, the device structure design, the fabrication process, and the substrate materials are all crucial factors to optimized the output perfomance of PMEHs. Early studies of PMEHs are mostly based on silicon substrate with conventional MEMS processes [1][2][3][4], the chip area of these PMEHs are usually small and with higher resonant frequencies in around kHz range. Although the normalized power density (NPD) of silicon based PMEHs can be high, the devices are difficult to find real field applications because the mechanical vibration frequencies are usually in low frequencies.…”