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Maskless Arrayed Nanofiber Mats by Bipolar Pyroelectrospinning
摘要： The numerous advantages of micro and nanostructures produced by electrospinning (ES) have stimulated enormous interest in this technology with potential application in several fields. However, ES has still some limitations in controlling the geometrical arrangement of the fibre mats so that expensive and time-consuming technologies are usually employed for producing ordered geometries. Here we present a technique that we call 'bipolar pyro-electrospinning' (b-PES) for generating ordered-arrays of fibre mats in a direct manner by using the bipolar pyroelectric field produced by a periodically poled lithium niobate crystal (PPLN). The b-PES is free from expensive electrodes, nozzles and masks because it makes use simply of the structured pyroelectric field produced by the PPLN crystal used as collector. The results show clearly the reliability of the technique in producing a wide variety of arrayed fibre mats that could find application in bioengineering or many others field. Preliminary results of live cells patterning under controlled geometrical constraints is also reported and discussed in order to show potential exploitation as scaffold in tissue engineering.
关键词： PDLLA,pyro-electrospinning,arrayed mats,pyroelectric effect,polymer fibres
更新于2025-09-23 15:22:29
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The Generated Entropy Monitored by Pyroelectric Sensors
摘要： Entropy generation in irreversible processes is a critical issue that affects the failure and aging of electrical, chemical or mechanical systems. The promotion of energy conversion ef?ciency needs to reduce energy losses, namely to decrease entropy generation. A pyroelectric type of entropy detector is proposed to monitor energy conversion processes in real time. The entropy generation rate can be derived from the induced pyroelectric current, temperature, thermal capacity, pyroelectric coef?cient and electrode area. It is pro?table to design entropy detectors to maintain a small thermal capacity while pyroelectric sensors minimize geometrical dimensions. Moreover, decreasing the electrode area of the PZT cells could avoid affecting the entropy variation of the measured objects, but the thickness of the cells has to be greatly reduced to promote the temperature variation rate and strengthen the electrical signals. A commercial capacitor with a capacitance of 47 μF and a maximum endured voltage of 4 V were used to estimate the entropy to act as an indicator of the capacitors’ time-to-failure. The threshold time was evaluated by using the entropy generation rates at about 7.5 s, 11.25 s, 20 s and 30 s for the applied voltages of 40 V, 35 V, 30 V and 25 V respectively, while using a PZT cell with dimensions of 3 mm square and a thickness of 200 μm.
关键词： sensor,entropy,energy conversion,pyroelectric effect,failure
更新于2025-09-23 15:21:21
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One-Structure-Based Multi-Effects Coupled Nanogenerators for Flexible and Self-Powered Multi-Functional Coupled Sensor Systems
摘要： The simultaneous monitoring of multi-physical signals is essential for future sensor systems, but is currently only realized by integrating a variety of sensor types into a single device. However, the ability to use a single sensor structure that shares common electrodes can provide a route to multi-functional sensing while also decreasing device size and increasing spatial resolution. Here we report a ferroelectric barium titanate film-based multi-effect coupled nanogenerator for scavenging light, mechanical, and thermal energies to realize a self-powered multi-functional coupled sensor system without using any external power source. The coupled nanogenerator exhibits a strong coupling enhancement with detection sensitivities of 0.42 nA/(mW/cm2) during illumination by 405 nm light, 1.43 nA/kPa for pressure detection, and -8.85 nA/K for temperature sensing, where both the light and pressure sensing performances have the highest sensitivities during a cooling temperature variation of ~19.5 K and the largest temperature detection sensitivity can be achieved during strong light illumination of 83.2 mW/cm2. Moreover, the coupled nanogenerator array can be integrated into flexible forms for tactile pressure, temperature, and light sensors, and enabling coupled sensing for the development of electronic skins.
关键词： photovoltaic effect,pyroelectric effect,piezoelectric effect,electronic skin
更新于2025-09-23 15:19:57
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Optimization of pyroelectric conversion of thermal energy through the PZT ceramic buzzer and natural convection
摘要： The main purpose of this work is to take advantage of the pyroelectric e?ect to produce electricity. We propose the use of the PZT ceramic buzzer, which possesses pyroelectric properties, to convert thermal energy into electrical energy by pyroelectric e?ect. We take advantage of natural convection to create temperature variation from a ?xed thermal source. The amount of power harvested by this technique is su?cient to supply low-power systems. Our experiment consists in subjecting the PZT ceramic buzzer to a temperature variation insured only by natural convection created in an oil bath. In order to verify the existence of thermal ?uctuations and con?rm the e?ciency of our technique, we use thermal imaging which shows that the temperature changes as a function of time. We propose in this paper an optimization of our energy-harvesting system by studying the e?ect of the convection system geometry on the pyroelectric response: the e?ect of volume on the pyroelectric response and the e?ect of the distance between the oil surface and the pyroelectric ceramic. It appears from our study that the harvested power increases when the distance between the buzzer and the ?uid decreases but it increases slightly with the volume of liquid.
关键词： pyroelectric effect,energy harvesting,thermal energy,PZT ceramic buzzer,natural convection
更新于2025-09-23 15:19:57
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Capabilities of GaN/AlN/GaN structures as high-intensity pyroelectric laser sensors
摘要： The use of transparent Al2O3 /GaN/AlN/GaN structures as pyrometric sensors for measuring the parameters of high-intensity laser pulses is proposed. The peculiarities of the employment of such sensors in laser fusion facilities are analysed. Post-pulse distributions of the absorbed energy density are obtained for various parameters of both GaN layers. The local maxima of these distributions are minimised by varying the ratio of donor concentration and the ratio of their thicknesses under the condition of invariance of the total absorbed energy. The optimal structure configuration is established in terms of reducing the possible negative effect of laser impact on the pyroelectric coefficient stability.
关键词： pyroelectric effect,aluminium nitride,laser thermonuclear fusion
更新于2025-09-16 10:30:52
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Understanding the Role of Ferroelastic Domains on the Pyroelectric and Electrocaloric Effects in Ferroelectric Thin Films
摘要： Temperature- and electric-field-induced structural transitions in a polydomain ferroelectric can have profound effects on its electrothermal susceptibilities. Here, the role of such ferroelastic domains on the pyroelectric and electrocaloric response is experimentally investigated in thin films of the tetragonal ferroelectric PbZr0.2Ti0.8O3. By utilizing epitaxial strain, a rich set of ferroelastic polydomain states spanning a broad thermodynamic phase space are stabilized. Using temperature-dependent scanning-probe microscopy, X-ray diffraction, and high-frequency phase-sensitive pyroelectric measurements, the propensity of domains to reconfigure under a temperature perturbation is quantitatively studied. In turn, the “extrinsic” contributions to pyroelectricity exclusively due to changes between the ferroelastic domain population is elucidated as a function of epitaxial strain. Further, using highly sensitive thin-film resistive thermometry, direct electrocaloric temperature changes are measured on these polydomain thin films for the first time. The results demonstrate that temperature- and electric-field-driven domain interconversion under compressive strain diminish both the pyroelectric and the electrocaloric effects, while both these susceptibilities are enhanced due to the exact-opposite effect from the extrinsic contributions under tensile strain.
关键词： electrocaloric effect,ferroelastic domains,ferroelectricity,pyroelectric effect,entropy
更新于2025-09-10 09:29:36
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Hybrid photosensitive structures based on nematic liquid crystals and lithium niobate substrates
摘要： Liquid crystal cells based on lithium niobate substrates have recently been proposed as good candidates for optofluidic devices and for light-induced controlled generation of defects in liquid crystal films. The peculiarity of these structures lies in the possibility of using the bulk photovoltaic effect of lithium niobate to obtain an optically induced dc field able to affect the molecular liquid crystal director. Reversible fragmentation and self-assembling of liquid crystal droplets driven by the lithium niobate pyroelectric properties have also been reported. We review the basic results obtained so far with the aim of making the point and seeing what else can be done in the framework of the realization of hybrid structures combining lithium niobate with the electro-optical and nonlinear optical properties of liquid crystals.
关键词： pyroelectric effect,optofluidic devices,lithium niobate,liquid crystals,photovoltaic effect
更新于2025-09-09 09:28:46
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Comprehensive Pyro‐Phototronic Effect Enhanced Ultraviolet Detector with ZnO/Ag Schottky Junction
摘要： As a coupling effect of pyroelectric and photoelectric effect, pyro-phototronic effect has demonstrated an excellent tuning role for fast response p–n junction photodetectors (PDs). Here, a comprehensive pyro-phototronic effect is utilized to design and fabricate a self-powered and flexible ultraviolet PD based on the ZnO/Ag Schottky junction. By using the primary pyroelectric effect, the maximal transient photoresponsivity of the self-powered PDs can reach up to 1.25 mA W?1 for 325 nm illumination, which is improved by 1465% relative to that obtained from the steady-state signal. The relative persistent secondary pyroelectric effect weakens the height of Schottky barrier, leading to a reduction of the steady-state photocurrent with an increase in the power density. When the power density is large enough, the steady-state photocurrent turns into a reverse direction. The corresponding tuning mechanisms of the comprehensive pyro-phototronic effect on transient and steady-state photocurrent are revealed based on the bandgap diagrams. The results may help us to further clarify the mechanism of the pyro-phototronic effect on the photocurrent and also provide a potential way to optimize the performance of self-powered PDs.
关键词： ultraviolet photodetector,Schottky junction,secondary pyroelectric effect,pyro-phototronic effect,self-powered
更新于2025-09-04 15:30:14