Real‐Time Operation of Photovoltaic Optoelectronic Tweezers: New Strategies for Massive Nano‐object Manipulation and Reconfigurable Patterning

Sebastián‐Vicente, Carlos; Muñoz‐Cortés, Esmeralda; Garcı́a-Cabañes, A.; Agulló‐López, F.; Carrascosa, M.

doi:10.1002/ppsc.201900233

Cited by 21 publications

(13 citation statements)

References 45 publications

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“…Better knowledge of the surface structure and its properties (including oxygen vacancies) [22,52] would offer the possibility of nanoscale devices, molecular detection, and efficient catalysts [54], among other applications. This remark is of special relevance in relation to real-time operation of optoelectronic (photovoltaic) tweezers in LiNbO3 and will advance our understanding of the trapping and untrapping cycles during their operation [55]. Furthermore, recent publications can be found in the literature showing potential applications in neuromorphic computing through the production of oxygen vacancies in LiNbO3 thin films by Ar + irradiation [56].…”

Section: Discussionmentioning

confidence: 78%

Real-Time Identification of Oxygen Vacancy Centers in LiNbO3 and SrTiO3 during Irradiation with High Energy Particles

et al. 2021

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Oxygen vacancies are known to play a central role in the optoelectronic properties of oxide perovskites. A detailed description of the exact mechanisms by which oxygen vacancies govern such properties, however, is still quite incomplete. The unambiguous identification of oxygen vacancies has been a subject of intense discussion. Interest in oxygen vacancies is not purely academic. Precise control of oxygen vacancies has potential technological benefits in optoelectronic devices. In this review paper, we focus our attention on the generation of oxygen vacancies by irradiation with high energy particles. Irradiation constitutes an efficient and reliable strategy to introduce, monitor, and characterize oxygen vacancies. Unfortunately, this technique has been underexploited despite its demonstrated advantages. This review revisits the main experimental results that have been obtained for oxygen vacancy centers (a) under high energy electron irradiation (100 keV–1 MeV) in LiNbO3, and (b) during irradiation with high-energy heavy (1–20 MeV) ions in SrTiO3. In both cases, the experiments have used real-time and in situ optical detection. Moreover, the present paper discusses the obtained results in relation to present knowledge from both the experimental and theoretical perspectives. Our view is that a consistent picture is now emerging on the structure and relevant optical features (absorption and emission spectra) of these centers. One key aspect of the topic pertains to the generation of self-trapped electrons as small polarons by irradiation of the crystal lattice and their stabilization by oxygen vacancies. What has been learned by observing the interplay between polarons and vacancies has inspired new models for color centers in dielectric crystals, models which represent an advancement from the early models of color centers in alkali halides and simple oxides. The topic discussed in this review is particularly useful to better understand the complex effects of different types of radiation on the defect structure of those materials, therefore providing relevant clues for nuclear engineering applications.

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Section: Discussionmentioning

confidence: 78%

Real-Time Identification of Oxygen Vacancy Centers in LiNbO3 and SrTiO3 during Irradiation with High Energy Particles

et al. 2021

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“…First preliminary results on light-induced ejection of Ag nanoparticles from a PV crystal were presented in a previous publication, which was focused on real-time operation of PVOT. [19] Figure 3 shows several experimental results that summarize the observed behavior. After deposition of a uniform background of Ag particles dispersed in heptane on a z-cut LN:Fe crystal, the PV substrate was excited by a focused Gaussian beam (see the Experimental Section).…”

Section: Light-induced Ejection Of Particles From Linbo 3 :Fe Surfacesmentioning

confidence: 93%

“…In ref. [19], where preliminary data on the ejection phenomenon with Ag nanoparticles were reported, it was suggested that this effect might occur due to a charge transfer between the illuminated PV ferroelectric crystal and the particles. According to this proposal, particles get charged with the same sign as the corresponding polar face (negative at the +c face and positive at the −c face), leading to Coulomb repulsion and ejection (see Figure 7a).…”

Section: Charge Transfer Between the Ferroelectric Crystal And Micro-...mentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8] In particular, a great potential has been shown for electric-fieldassisted manipulation and trapping of micro-/nanoparticles and biomaterials. [1,[9][10][11][12][13][14] The electric fields can be induced by different physical stimuli, such as visible light illumination via the bulk photovoltaic (PV) effect or temperature changes via the This issue was initially addressed in a recent paper, [19] where an alternative simultaneous procedure was explored: illumination of the PV crystal and particle manipulation are performed at the same time. Unexpectedly, when using the simultaneous method, a novel feature of PVOT was observed, which consists of an efficient Ag nanoparticle untrapping and ejection effect during illumination.…”

Section: Introductionmentioning

confidence: 99%

“…[10,17,18] for PY trapping.The particle ejection phenomenon reported in this paper has been incidentally discovered during particle manipulation with PVOT. [19] The so-called PVOT are a rather recent technique that has undergone a rapid development in the last few years, [16] based on the electric fields generated by the bulk PV effect. This effect is a singular phenomenon which strongly appears in a few crystalline ferroelectric materials, [20,21] such as LiNbO 3 (LN), when properly doped (mainly Fe or Cu).…”

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confidence: 99%

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Light and Thermally Induced Charge Transfer and Ejection of Micro‐/Nanoparticles from Ferroelectric Crystal Surfaces

Sebastián‐Vicente

Garcı́a-Cabañes

Agulló‐López

et al. 2021

Adv Elect Materials

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pyroelectric (PY) effect, allowing handling and trapping particles being close to the ferroelectric platform. Numerous works have been reported on these techniques and their multiple applications. Some reviews or reference works are refs. [12,15,16] for photovoltaic optoelectronic tweezers (PVOT), and refs. [10,17,18] for PY trapping.The particle ejection phenomenon reported in this paper has been incidentally discovered during particle manipulation with PVOT. [19] The so-called PVOT are a rather recent technique that has undergone a rapid development in the last few years, [16] based on the electric fields generated by the bulk PV effect. This effect is a singular phenomenon which strongly appears in a few crystalline ferroelectric materials, [20,21] such as LiNbO 3 (LN), when properly doped (mainly Fe or Cu). It allows the generation of remarkably high electric fields (up to ≈1.5 × 10 5 V cm −1 ) [22] for moderate or low light excitation levels (around mW cm −2 ). The PV effect is associated with optical transitions from localized states of impurities, such as Fe 2+ /Fe 3+ or Cu + /Cu 2+ , and with a directional electron migration along the polar axis (PV current). Once displaced, the electrons are trapped in other defects and generate a spatial charge distribution and the corresponding electric field, [23] which are illustrated in Figure 1. Two crystal configurations (parallel and perpendicular), commonly used for particle manipulation, are shown. [24,25] They are defined by the orientation of the polar axis, parallel or perpendicular to the active surface, respectively. The PV electric field extends near the surface outside the crystal (evanescent PV fields), where it can act either on charged particles via electrophoretic forces, or on neutral objects polarized by the field via dielectrophoretic forces, [26,27] as illustrated in Figure 1.So far, the vast majority of the reported experimental results have been obtained by using a two-step sequential procedure: first, the PV substrate is illuminated, and then, the particles are manipulated and trapped by means of the light-induced PV electric fields. This sequential method can be employed because the PV fields remain after illumination for periods of time in the range of days to months unless they are thermally erased or externally screened. Although this method is quite convenient to trap particles and assemble permanent particle structures, other applications require real-time manipulation.During real-time operation of photovoltaic optoelectronic tweezers, a novel intriguing phenomenon has been recently observed, namely, silver nanoparticles previously deposited on ferroelectric LiNbO 3 :Fe surfaces are ejected from them by illumination. Here, it is shown that this phenomenon results from the electrical charging of the micro-/nanoparticles previously trapped on the LiNbO 3 :Fe surfaces and the subsequent Coulomb repulsion. Specific experiments are performed to determine the sign of the transferred charges, which is negative/positive for the +c/−c sample face...

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Light‐Induced Virtual Electrodes for Microfluidic Droplet Electro‐Coalescence

Zamboni,

Sebastián‐Vicente,

Denz

et al. 2023

Adv Funct Materials

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Electro‐coalescence is the fusion phenomenon between a pair or more microfluidic droplets that are immersed in an immiscible medium under an electric field. This technique is frequently used to merge confined droplets in surfactant‐stabilized microfluidic emulsions using local electric fields. Despite the necessity of miniaturized electrodes, this method has proven highly successful in microfluidics and lab‐on‐a‐chip applications. Miniaturized electrodes severely curtail the spatial and temporal flexibility of the electric potential, thus hindering real‐time and flexible operation and leading to high production costs. The current study addresses this problem with reconfigurable electric field potential by light‐driven functional virtual electrodes. These electrodes are light‐induced on a non‐centrosymmetric ferroelectric photovoltaic crystal placed below a microfluidic droplet channel. The photovoltaic effect in the crystal is responsible for the space charge distributions that act as virtual electrodes, whose evanescent field is screened by free charges into the two liquids inside the channel. A numerical model is developed to describe the evolution of the evanescent electric field causing electro‐coalescence. Based on this prediction, two coalescence processes occur at two different timescales and with different numbers of droplets involved. Controlled exposure time modulation allows either rapid on‐demand coalescence of droplet pairs or breakup of the entire emulsion.

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Real‐Time Operation of Photovoltaic Optoelectronic Tweezers: New Strategies for Massive Nano‐object Manipulation and Reconfigurable Patterning

Cited by 21 publications

References 45 publications

Real-Time Identification of Oxygen Vacancy Centers in LiNbO3 and SrTiO3 during Irradiation with High Energy Particles

Real-Time Identification of Oxygen Vacancy Centers in LiNbO3 and SrTiO3 during Irradiation with High Energy Particles

Light and Thermally Induced Charge Transfer and Ejection of Micro‐/Nanoparticles from Ferroelectric Crystal Surfaces

Light‐Induced Virtual Electrodes for Microfluidic Droplet Electro‐Coalescence

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