Electrophoretic versus dielectrophoretic nanoparticle patterning using optoelectronic tweezers

Currently, there is increasing interest from many scientific disciplines in the development of systems that are able to sort and arrange many objects in parallel at the nano-and micrometric scale. Among others, photovoltaic tweezers (PVT) are an optoelectronic technique for trapping and patterning nano-and micro-objects in accordance with an arbitrary light profile. In this work, the differential features of electro-and dielectrophoretic (EP and DEP) nanoparticle (NP) patterning using PVT are deeply investigated. The study is carried out through theory and experiments. The developed theory extends the applicability of a previously reported model to be able to compute EP potentials and to obtain numerical values for the EP and DEP potential energies. Two-dimensional patterns of charged and neutral aluminum NPs are fabricated on top of Fe:LiNbO3 crystals, and different light distributions and other experimental parameters (crystal thickness and NP concentration) are compared. Patterns of charged and neutral NPs show remarkable differences in both particle density distribution and fidelity to the original light profile. The observed different features between EP and DEP trapping are satisfactorily explained by the theoretical analysis. The results provide routes for the optimization of the NP arrangements for both regimes.This work is supported by the Spanish Ministerio de Economía y Competitividad under Grant No. MAT201457704-C3. J.F.M.-M. is partially supported by a fellowship of the Universidad Politécnica de Madrid (Grant No. RR01/2016

Light-assisted patterning of salt precipitation on photovoltaic LiNbO3 substrates

The control of salt crystallization on a surface has important implications in many technological and industrial applications. In this work, we propose and demonstrate an optoelectrical method to define and control the spatial distribution of salt crystallization on a lithium niobate photovoltaic substrate. It is based on the bulk photovoltaic effect that generates an electric field on the illuminated regions of the crystal. The salt only crystallizes on these illuminated regions of the substrate. Single salt spots or more complicated spatial patterns, defined by the light intensity spatial distribution, have been achieved. In particular, some results have been obtained using scanning/moving laser beams, i.e., “drawing” the saline patterns. The role of light exposure time and salt concentration in the aqueous solution has been studied. The method has been checked with several salts with successful results showing its general applicability. A discussion on the possible physical mechanisms behind the method and their implication for the operation of photovoltaic platforms in other applications is also include

Combinatorial nanoparticle patterns assembled by photovoltaic optoelectronic tweezers

Photovoltaic optoelectronic tweezers (PVOTs) have been proven to be an efficient tool for the manipulation and massive assembly of micro/nano-objects. The technique relies on strong electric fields produced by certain ferroelectric materials upon illumination due to the bulk photovoltaic effect (customarily LiNbO3:Fe). Despite the rapid development of PVOTs and the achievement of high-quality 1D and 2D particle patterning, research efforts aimed at the fabrication of combinatorial structures made up of multiple types of particles have been scarce. Here, we have established the working principles of three different methods to tackle this pending challenge. To that end, dielectrophoresis and/or electrophoresis acting on neutral and charged particles, respectively, have been suitably exploited. Simple mixed structures combining metallic and dielectric nanoparticles of different sizes have been obtained. The results lay the groundwork for future fabrication of more complex combinatorial structures by PVOT, where micro/nanoparticles are the basic building blocks of miniaturized functional device

Droplet ejection and liquid jetting by visible laser irradiation in pyro-photovoltaic Fe-doped LiNbO3 platforms

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 patterningThis work was sponsored by Ministerio de Ciencia, Innovación y Universidades of Spain under grant MAT2017-83951-R. A.P. acknowledges the grant no. PEJ2018-003989 from the Iniciativa de Empleo Juvenil y Fondo Social Europeo, and was supported by the MIUR project “Piattaforma Modulare Multi Missione” (PM3), ARS01_01181. Open Access Funding provided by Consiglio Nazionale delle Ricerche within the CRUI-CARE Agreemen

All-optical domain inversion in LiNbO3 crystals by visible continuous-wave laser irradiation

LiNbO3 is a distinguished multifunctional materialwhere ferroelectric domain engineering is of paramount impor-tance. This degree of freedom of the spontaneous polarizationremarkably enhances the applicability of LiNbO3, for instance, inphotonics. In this work, we report the first method for all-opticaldomain inversion of LiNbO3 crystals using continuous-wave visiblelight. While we focus mainly on iron-doped LiNbO3, theapplicability of the method is also showcased in undoped congruentLiNbO3. The technique is simple, cheap, and readily accessible. Itrelies on ubiquitous elements: a light source with low/moderateintensity, basic optics, and a conductive surrounding medium, e.g.,water. Light-induced domain inversion is unequivocally demon-strated and characterized by combination of several experimentaltechniques: selective chemical etching, surface topography profilometry, pyroelectric trapping of charged microparticles, scanningelectron microscopy, and 3D Čerenkov microscopy. The influence of light intensity, exposure time, laser spot size, and surroundingmedium is thoroughly studied. To explain all-optical domain inversion, we propose a novel physical mechanism based on ananomalous interplay between the bulk photovoltaic effect and external electrostatic screening. Overall, our all-optical method offersstraightforward implementation of LiNbO3 ferroelectric domain engineering, potentially sparking new research endeavors aimed atnovel optoelectronic applications of photovoltaic LiNbO3 platformsPID2020-116192RB-I0, TED2021-129937B−I00, S2018/NMT-4291 TEC2SPAC

Compuesto para la elaboración de un medicamento de fototerapia

Compuesto para la elaboración de un medicamento de fototerapia. La presente invención se refiere al uso de un compuesto con efecto fotovoltaico en volumen para la elaboración de un medicamento de fototerapia para la prevención o el tratamiento de un proceso patológico como, por ejemplo, un tumor o un cáncer, una enfermedad inflamatoria y/o autoinmune, un proceso patológico asociado a angiogénesis o a proliferación mio-endotelial anormal o no deseada, una fibrosis o un proceso patológico asociado a fibrosis; para la prevención o el tratamiento de una afección o una enfermedad dermatológica o para el tratamiento de una enfermedad infecciosa de origen vírico, fúngico, bacteriano o parasitario.Peer reviewedUniversidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, Consejo Superior de Investigaciones Científicas (España)A1 Solicitud de patentes con informe sobre el estado de la técnic

Optoelectronic manipulation, trapping, splitting, and merging of water droplets and aqueous biodroplets based on the bulk photovoltaic effect

Optical and optoelectronic techniques for micro- A nd nano-object manipulation are becoming essential tools in nano- A nd biotechnology. The use of photovoltaic optoelectronic tweezers is a remarkable optoelectronic technique that has undergone rapid development in recent years, with excellent results and widespread potential applications. It is based on light-induced electric fields generated by the bulk photovoltaic effect in certain ferroelectrics, such as LiNbO3. The technique is simple and versatile, enabling the successful manipulation of a large variety of micro- A nd nano-objects with only optical control, without the need for electrodes or power supplies. However, the handling of objects in aqueous solutions remains a challenge for this tool, due to the electric-screening effects of polar liquids. This has hindered their application in biotechnology and biomedicine, where most processes occur in aqueous solution. Here, an efficient route to overcome this problem is proposed and demonstrated. It uses photovoltaic optoelectronic tweezers to manipulate aqueous droplets, immersed in a nonpolar oil liquid, but hanging at the air-oil interface. In this singular configuration, the high electric fields generated by the bulk photovoltaic effect in the LiNbO3 substrate allow simple and flexible manipulation of aqueous droplets controlled by the light. Droplet guiding, trapping, merging, and splitting are achieved and efficient operation with water and a variety of biodroplets (DNA, sperm, and phosphate-buffered saline solutions) is demonstrated. A discussion on the physical mechanisms responsible for the manipulation processes is also provided. The reported results overcome the main limitation of these tweezers to handle biomaterials and promise high potential for biotechnological and biochemistry applications, including their implementation in optofluidic devicesFinancial support from Ministerio de Ciencia, Innovación y Universidades of Spain (MAT2017-83951-R) is gratefully acknowledged. A. Puerto acknowledges the funding under Iniciativa de Empleo Juvenil y Fondo Social Europeo (PEJ2018-003989

Fabrication of Periodically Poled Swift Ion-irradiation Waveguides in LiNbO3

Periodically poled swift-ion irradiated waveguides have been prepared following two different methods: i) Ion irradiation of two types of periodically poled lithium niobate (PPLN), that is, Czochralski off-centred grown PPLN and external electrical field PPLN. After the ion irradiation, the domain structure of the original PPLN was preserved and the waveguides were also proved functional. ii) Electric periodical poling of previously fabricated swift-ion irradiated waveguides. The periodic polarization of the ion irradiated waveguide was achieved for the first time to our knowledge. In both cases, the combination of PPLN with optical waveguide structures created by swift-ion irradiation, which have good nonlinear and electrooptical properties, and high optical confinement, gives rise to quite good candidates for nonlinear optical devices. © Taylor & Francis 2009Peer Reviewe