Investigation of pyroelectric electron emission from monodomain lithium niobate single crystals

Investigation on the behavior of nematic liquid crystals on functionalized polar dielectric crystal substrates is accomplished. Very interesting effects can be observed in maneuvering liquid crystal droplets on the substrate surface, driven by electric fi elds generated by pyroelectric effect. Reversible drops fragmentation and self-assembling in different confi gurations can be achieved. The dynamics of the observed phenomena is studied and the repeatability of the process is full assessed.

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“…The basis of the phenomenon is, as said above, the pyroelectric effect in PPLN 69, 70. When temperature T is constant, i.e.…”

Section: Liquid Crystal's Fragmentation and Self‐patterningmentioning

confidence: 99%

Reversible Fragmentation and Self‐Assembling of Nematic Liquid Crystal Droplets on Functionalized Pyroelectric Substrates

Merola

Grilli

Coppola

et al. 2012

Adv Funct Materials

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“…, where Δ P i is the coefficient of the polarization vector and p i is the pyroelectric coefficient. At equilibrium, all P s in the crystal are fully screened by the external screening charge and no electric field exists [37]. The change of the polarization, occurring with temperature variation, perturbs such equilibrium, causing a lack or excess of surface screening charge.…”

Section: Interpretation Of the Phenomenonmentioning

confidence: 99%

“…Consequently, an electrostatic state appears and generates a high electric field at the crystal surface [38,39]. Figures 3(a) According to the pyroelectric effect [37] the heating process makes the polarization magnitude to decrease, thus leaving surface screening charges uncompensated (see Fig. 3(b) top).…”

Section: Interpretation Of the Phenomenonmentioning

confidence: 99%

Liquid micro-lens array activated by selective electrowetting on lithium niobate substrates

Grilli¹,

Miccio²,

Vespini³

et al. 2008

Opt. Express

130

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Lens effect was obtained in an open microfluidic system by using a thin layer of liquid on a polar electric crystal like LiNbO3. An array of liquid micro-lenses was generated by electrowetting effect in pyroelectric periodically poled crystals. Compared to conventional electrowetting devices, the pyroelectric effect allowed to have an electrode-less and circuit-less configuration. An interferometric technique was used to characterize the curvature of the micro-lenses and the corresponding results are presented and discussed. The preliminary results concerning the imaging capability of the micro-lens array are also reported.

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“…This is the manifestation of the spontaneous polarization change ∆P s following to a temperature variation , where ∆P i is the coefficient of the polarization vector and p i is the pyroelectric coefficient. At equilibrium, all P s in the crystal are fully screened by the external screening charge and no electric field exists [14]. The change of the polarization perturbs this equilibrium state causing a lack or excess of surface screening charge, an electric field appears at the crystal surface.…”

Section: Experimental Observationmentioning

confidence: 99%

Tunable liquid microlens array driven by pyroelectric effect: full interferometric characterization

et al. 2008

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Liquid lenses with adjustable focal length are of great interest in the field of microfluidic devices. They are, usually, realized by electrowetting effect after electrodes patterning on a hydrofobic substrate. Applications are possible in many fields ranging from commercial products such as digital cameras to biological cell sorting. We realized an open array of liquid lenses with adjustable focal length without electrode patterning. We used a z-cut Lithium Niobate crystal (LN) as substrate and few microliters of an oily substance to obtain the droplets array. The spontaneous polarization of LN crystals is reversed by the electric field poling process, thus enabling the realization of periodically poled LN (PPLN) crystals. The substrate consists of a two-dimensional square array of reversed domains with a period around 200 µm. Each domain presents an hexagonal geometry due to the crystal structure. PPLN is first covered by a thin and homogeneous layer of the above mentioned liquid and therefore its temperature is changed by means of a digitally controlled hot plate. During heating and cooling process there is a rearrangement of the liquid layer until it reaches the final topography. Lenses formation is due to the superficial tension changing at the liquid-solid interface by means of the pyroelectric effect. Such effect allows to create a two-dimensional lens pattern of tunable focal length without electrodes. The temporal evolution of both shape and focal length lenses are quantitatively measured by Digital Holographic Microscopy. Array imaging properties and quantitative analysis of the lenses features and aberrations are presented.

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Investigation of pyroelectric electron emission from monodomain lithium niobate single crystals

Cited by 26 publications

References 28 publications

Reversible Fragmentation and Self‐Assembling of Nematic Liquid Crystal Droplets on Functionalized Pyroelectric Substrates

Reversible Fragmentation and Self‐Assembling of Nematic Liquid Crystal Droplets on Functionalized Pyroelectric Substrates

Liquid micro-lens array activated by selective electrowetting on lithium niobate substrates

Tunable liquid microlens array driven by pyroelectric effect: full interferometric characterization

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