Miso Kim

An electromechanically coupled model for a cantilevered piezoelectric energy harvester with a proof mass is presented. Proof masses are essential in microscale devices to move device resonances towards optimal frequency points for harvesting. Such devices with proof masses have not been rigorously modeled previously; instead, lumped mass or concentrated point masses at arbitrary points on the beam have been used. Thus, this work focuses on the exact vibration analysis of cantilevered energy harv

Phononic crystals (PnCs) have been utilized to amplify the amount of input energy transferred to a piezoelectric energy harvesting (PEH) device by manipulating elastic wave propagation. When introducing a defect that has material properties and/or geometry different from a unit cell, mechanical resonance of the defect leads to localizing elastic waves inside the defect. This is called a defect mode. Several prior studies have explored a defect mode for PEH purpose; however, they have focused onl

Gradient-index (GRIN) refers to a system where the refractive index changes spatially within a specific region. GRIN phononic crystals are capable of not only amplifying the magnitude of wave energies but also controlling the directional nature of the wave propagation, thus offering substantial benefits with regard to energy harvesting (EH) improvements. Here, we propose a systematic design method for GRIN phononic crystals which combine the two-dimensional Reissner–Mindlin plate model and a gen

Harvesting efficiency of a piezoelectric vibration energy harvesting system is investigated to provide design guidelines for harvesting devices with optimal performance. Harvesting power efficiency (η), defined as the ratio of device output power (Pout) to mechanical input power (Pin), is an essential but unexplored metric for comparison of harvesters operating in different power-input environments. Power extracted from piezoelectric harvesters has been of primary interest and proper accounting

Electrospun piezoelectric polymer fibers, which offer mechanical flexibility, light weight, and relatively low temperature processing, have emerged as a strong solution to shape-adaptive energy harvesting and sensing applications for smart electronics at multi-scales. In this work, we aim to enhance the electrospun fiber-based piezoelectric energy harvesting performance by elucidating the role of the solvent in crystallization kinetics and fiber formation during electrospinning as well as its in

Electrospun polymeric piezoelectric fibers have a considerable potential for shape-adaptive mechanical energy harvesting and self-powered sensing in biomedical, wearable, and industrial applications. However, their unsatisfactory piezoelectric performance remains an issue to be overcome. While strategies for increasing the crystallinity of electroactive β phases have thus far been the major focus in realizing enhanced piezoelectric performance, tailoring the fiber morphology can also be a promis

Abstract This study aims to investigate elastic wave localization that leverages defect band splitting in a phononic crystal with double defects through in-depth analysis of comparison of numerical and experimental results. When more than one defect is created inside a phononic crystal, these defects can interact with each other, resulting in a distinctive physical phenomenon from a single defect case: defect band splitting. For a phononic crystal consisting of circular-hole type unit cells in a

Abstract Piezoelectric polymer fibers offer a fundamental element in intelligent fabrics with their shape adaptability and energy‐conversion capability for wearable activity and health monitoring applications. Nonetheless, realizing high‐performance smart polymer fibers faces a technical challenge due to the relatively low piezoelectric performance. Here, we demonstrate high‐performance piezoelectric yarns simultaneously equipped with structural robustness and mechanical flexibility. The key to