Dynamics of a piezoelectric beam subjected to water droplet impact with water layer formed on the surface

Wong, Voon‐Kean; Ho, Jee-Hou; Yap, Eng Hwa

doi:10.1177/1045389x14549871

Cited by 18 publications

(18 citation statements)

References 24 publications

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“…Furthermore, while the stiffer cantilever oscillated at its natural eigenfrequency ( f 0 = 112 Hz), the softer substrate showed an additional higher order oscillation ( f 0 = 11 and f 1 = 68 Hz). The time scales of droplet spreading and recoil (~10 ms) were much shorter than the first order oscillation timescale (~100 ms) for the low stiffness substrate, resulting in the inability to accelerate the droplet upwards (see Supplementary Video S6 ), and enabling full droplet recoil before lift-off with similar contact times as those on a rigid superhydrophobic surface 21 22 . To enable contact time reduction, our results show that the substrate oscillation and droplet impact timescales must be on the same order of magnitude.…”

Section: Resultsmentioning

confidence: 99%

Water droplet impact on elastic superhydrophobic surfaces

Weisensee

Tian

Miljkovic

et al. 2016

Sci Rep

155

149

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Water droplet impact on surfaces is a ubiquitous phenomenon in nature and industry, where the time of contact between droplet and surface influences the transfer of mass, momentum and energy. To manipulate and reduce the contact time of impacting droplets, previous publications report tailoring of surface microstructures that influence the droplet - surface interface. Here we show that surface elasticity also affects droplet impact, where a droplet impacting an elastic superhydrophobic surface can lead to a two-fold reduction in contact time compared to equivalent rigid surfaces. Using high speed imaging, we investigated the impact dynamics on elastic nanostructured superhydrophobic substrates having membrane and cantilever designs with stiffness 0.5–7630 N/m. Upon impact, the droplet excites the substrate to oscillate, while during liquid retraction, the substrate imparts vertical momentum back to the droplet with a springboard effect, causing early droplet lift-off with reduced contact time. Through detailed experimental and theoretical analysis, we show that this novel springboarding phenomenon is achieved for a specific range of Weber numbers (We >40) and droplet Froude numbers during spreading (Fr >1). The observation of the substrate elasticity-mediated droplet springboard effect provides new insight into droplet impact physics.

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Section: Resultsmentioning

confidence: 99%

Water droplet impact on elastic superhydrophobic surfaces

Weisensee

Tian

Miljkovic

et al. 2016

Sci Rep

155

149

View full text Add to dashboard Cite

show abstract

“…The water layer increases until it reaches the edges of the harvester and there is a spill. This unsteady behavior has some important effects on harvester dynamics [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…When there is a water layer of sufficient depth on the harvester surface, the impact of raindrops generates water ripples that causes additional gravity loads on the harvester surface [17].…”

Section: Introductionmentioning

confidence: 99%

Development of a Novel Piezoelectric Harvester Excited by Raindrops

Doria

Fanti

Filipi

et al. 2019

Sensors

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The impact of raindrops on a dry surface leads to a splashing phenomenon that dissipates a lot of energy. To improve energy collection, a novel piezoelectric raindrop energy harvester equipped with a spoonful of water was developed. The advantages and the drawbacks of this solution were analyzed with the aid of numerical simulations. A series of experimental tests were carried out in a laboratory with simulated raindrops. Experimental results showed that the negative effect of the added water mass was exceeded by the positive effects related to the impact of the raindrop on a liquid surface. Tests carried out connecting the harvester to a resistive load showed that the prototype was able to collect more energy than a simple cantilever harvester.

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“…In this case, a distributed parameter model is advantageous which allows to accurately predict the electromechanical behaviors of the beam by means of accurate strain distribution. Based on the model developed by Sodano et al [ 30 ] using Rayleigh–Ritz theorem and Hamilton’s principle, Wong et al [ 31 ] tried to model both the impact force of droplet and the force generated by the water ripple on a PZT cantilever through applying the distributed parameter method. Results showed that the presence of water layer on an untreated beam surface decreased the dominant frequency so as the voltage output.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Response of PVDF Cantilever Due to Droplet Impact Using an Electromechanical Model

Hao

Dong

et al. 2020

Sensors

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The dynamic response of a polyvinylidene fluoride (PVDF) cantilever beam under excitation of water droplet impact is investigated by developing an electromechanical model. In the model, the governing equations of beam motion and output voltage are derived in the theoretical way, such that the voltage across the PVDF layer and the cantilever deflection can be predicted. The motion of the beam is described by the multi-mode vibration model through which more accurate results can be obtained. The predicted results of the model are validated by the experiment. Combined with the experiment and the model, the effect of surface wettability on droplet-substrate interaction mechanisms is investigated, which provides an insight into the improvement of mechanical-to-electrical energy conversion efficiency in raindrop energy harvesting (REH) applications. Results show: (1) the droplet splash on a super-hydrophobic beam surface has a positive effect on voltage generation. The splash limit that affects the reaction force of the impacting droplet is experimentally determined and greatly dominant by the Weber number. (2) Small-scaled droplets in splash regime allow generating higher voltage output from a super-hydrophobic beam surface than from an untreated hydrophilic beam surface. (3) Tests of successive droplet impacts also show that a super-hydrophobic surface performs better over a hydrophilic surface by producing constant peak voltage and higher electrical energy harvested. In this case, the voltage measured from the hydrophilic surface decreases gradually as the water layer is accumulated. Overall, the electromechanical behaviors of a super-hydrophobic PVDF cantilever sensor can be well predicted by the model which shows a great potential in energy harvesting by maximizing the inelastic collision upon droplet-substrate interactions.

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Dynamics of a piezoelectric beam subjected to water droplet impact with water layer formed on the surface

Cited by 18 publications

References 24 publications

Water droplet impact on elastic superhydrophobic surfaces

Water droplet impact on elastic superhydrophobic surfaces

Development of a Novel Piezoelectric Harvester Excited by Raindrops

Dynamic Response of PVDF Cantilever Due to Droplet Impact Using an Electromechanical Model

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