Droplet Ejection and Liquid Jetting by Visible Laser Irradiation in Pyro‐Photovoltaic Fe‐Doped LiNbO₃ Platforms

Abstract

Controlling liquid dispensing and jetting from a reservoir drop or a liquid film require strong electric fields. One efficient method proposed some years ago is based on the high pyroelectric‐electrohydrodynamic (EHD) effect presented by lithium niobate when it undergoes a high temperature change. Additionally, first experiments generating droplets using the photovoltaic effect of Fe‐doped lithium niobate crystal (LiNbO3:Fe) have been recently reported. Here, it is shown how the excitation of the photovoltaic and pyroelectric effects of LiNbO3:Fe by visible light irradiation allows droplet dispensing and jetting. A basic characterization of the process, including the important role of the excitation light intensity, is reported. The experimental investigation demonstrates that efficient droplet ejection and liquid jetting can be easily achieved in different optical configurations and with various liquid solutions (water, alcohol, aqueous suspension of particles or polymers). This new explored method is analyzed by discussing some of its intrinsic and attractive advantages, namely the flexible and versatile control offered by light excitation and the activation of the photovoltaic and pyroelectric effects. The results let us to foresee that this strategy will have very good chances to become a viable inkjet printing method for addressing new challenges in directed liquid dispensing and patterning.

Optical manipulation of sessile droplets of nematic liquid crystalline materials on the surface of a photovoltaic crystal

“…Similar effects were widely investigated with droplets of conventional liquids, such as water, exposed to strong electric fields and are known as Taylor cones, electrohydrodynamic tip-streaming, cone-jetting, Rayleigh jets, etc. 23,[37][38][39][40][41] Granda et al 42 recently demonstrated that subcritical electric fields do not only stretch the liquid drops into filaments but can also cause their fingering into trilobite-like configurations, very similar to the one shown in Fig. 8(c).…”

“…Similar effects were widely investigated with droplets of conventional liquids, such as water, exposed to strong electric fields and are known as Taylor cones, electrohydrodynamic tip-streaming, cone-jetting, Rayleigh jets, etc 23 , 37 – 41 Granda et al 42 .…”

“…The results reported before 2018 are reviewed in the paper of García-Cabañes et al 22 . From papers published after 2018, we would like to point out the work of Puerto et al 23 . on droplet ejection and liquid jetting induced by laser irradiation of a LN:Fe platform, and the work of Zaltron et al 24 .…”

“…Most research on the manipulation of sessile liquid droplets on the LN surface was performed with pure water and aqueous dispersions of different mostly organic materials. The results reported before 2018 are reviewed in the paper of García-Cabañes et al 22 From papers published after 2018, we would like to point out the work of Puerto et al 23 on droplet ejection and liquid jetting induced by laser irradiation of a LN:Fe platform, and the work of Zaltron et al 24 on actuation and guiding of motion, merging and splitting of droplets by the LN:Fe-based optofluidic platform. In contrast to standard liquids, reports on experiments with droplets of standard (non-ferroelectric) NLC compounds are very rare.…”

Determination of the Dielectrophoretic Force Induced by the Photovoltaic Effect on Lithium Niobate

“…However, it requires the realization of electrodes and their cumbersome connection to voltage suppliers. A promising alternative to the presence of metallic electrodes is based on the photovoltaic effect exhibited inside certain ferroelectrics, such as lithium niobate, LiNbO 3 [16][17][18]. Upon appropriate illumination, an electric field is generated within the material with a strength that can be as high as 200 kV/cm and photoinduced charges are redistributed on the surface [19].…”