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Continuous tremor monitoring in Parkinson's disease: A wristwatch-inspired triboelectric sensor approach
(2024-12-20)
Ukasi, Sirinya
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Pongampai, Satana
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Panigrahi, Basanta Kumar
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Panda, Swati
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Hajra, Sugato
Parkinson's disease (PD) prevalence is projected to reach 12 million by 2040. Wearable sensors offer a promising approach for comfortable, continuous tremor monitoring to optimize treatment strategies. Here, we present a wristwatch-like triboelectric sensor (WW-TES) inspired by automatic watches for unobtrusive PD tremor assessment. The WW-TES utilizes a free-standing design with a surface-modified polytetrafluoroethylene (PTFE) film and a stainless-steel rotor within a biocompatible polylactic acid (PLA) package. Electrode distance is optimized to maximize the output signal. We propose and discuss the WW-TES working mechanism. The final design is validated for activities of daily living (ADLs), with varying signal amplitudes corresponding to tremor severity levels (“normal” to “severe”) based on MDS-UPDRS tremor frequency. Wavelet packet transform (WPT) is employed for signal analysis during ADLs. The WW-TES demonstrates the potential for continuous tremor monitoring, offering an accurate screening of severity and comfortable, unobtrusive wearability.
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Modified energy storage properties of lead-free Sr0.3Bi0.35Na0.335Li0.015TiO3 ceramics with La3+ substitution via the solid-state combustion technique
(2024-12-01)
Sinkruason, Thanapon
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Luangpangai, Anupong
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Julphunthong, Phongthorn
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Rittidech, Aurawan
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Suthapintu, Aekasit
In this study, the influence of La3+ substitution on the phase structure, microstructure, electrical and energy storage properties of (Sr<inf>0.3</inf>Bi<inf>0.35</inf>Na<inf>0.335</inf>Li<inf>0.015</inf>)<inf>1-x</inf>La<inf>x</inf>TiO<inf>3</inf> (SBNLT-xLa) ceramics with x = 0–0.05, using the solid-state combustion technique, was investigated. X-ray diffraction (XRD) patterns indicated a pure perovskite structure formed, along with coexisting rhombohedral and tetragonal phases in all ceramics. The Rietveld refinement analysis showed the tetragonal phase increased while the rhombohedral phase decreased with increased La3+ content. The morphology of the SBNLT-xLa ceramics displayed polygonal grain shapes and anisotropic grain growth. Average grain sizes increased from 2.01 to 2.43 μm as x increased from 0 to 0.01 and afterwards decreased as x increased further. Both the measured density and maximum dielectric constant (ɛ<inf>m</inf>) decreased from 5.48 to 5.29 g/cm3 and from 4667 to 2313, respectively, when x increased from 0 to 0.05. A decrease in the dielectric properties caused by the phase ratio shifting away from a morphotropic phase boundary (MPB) condition, poor microstructure and low density was produced with La3+ replacement. The maximum polarization (P<inf>max</inf>), remnant polarization (P<inf>r</inf>) and coercive field (E<inf>c</inf>) decreased with increased La3+ content. A decline in P<inf>r</inf> and E<inf>c</inf> improved the energy storage efficiency (ƞ) and energy storage loss (W<inf>loss</inf>), resulting in enhanced energy storage properties. At x = 0.02, the ceramic showed good energy storage properties (W<inf>total</inf> of 0.781 J/cm3, W<inf>rec</inf> of 0.624 J/cm3, W<inf>loss</inf> of 0.157 J/cm3 and ƞ of 79.8%), measured at 60 kV/cm.
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High-performance flexible lead-free piezo-antiferroelectric based on NaNbO3/PDMS composites for energy harvesting application
(2024-12-01)
Sumang, Rattiphorn
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Charoonsuk, Thitirat
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Vittayakorn, Naratip
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Panpho, Phakakorn
To bring the rapidly advancing technology of energy harvesters into commercial use, further development is required for devices that can enhance output performance, flexibility, ease of fabrication, and low cost. A hybrid concept is a promising method. It combines between the piezoelectric nanogenerator (PENG) and the triboelectric nanogenerator (TENG) to provide a high-performance nanogenerator. This study introduced a high-performance hybrid PENG and TENG device that operates using a NN-BNT/PDMS composite film. The NN-BNT/PDMS composite based nanogenerators were fabricated with varying NN-BNT content. Then, dielectric test and electrical properties were investigated. Adding NN-BNT into the PDMS composite film resulted in a higher dielectric constant compared to pure PDMS, leading to increase of electrical output. Under the optimal condition of a 3 wt%. NN-BNT composite based hybrid nanogenerator, the electrical output was significantly enhanced, reaching 40 V, 0.95 μA/cm2, and 200 μW/cm2 compared to pure PDMS. This nanogenerator further used to the charging of a capacitor to a voltage of around 1 V within 5 s and also powered multiple LEDs. The successful development of this highly efficient NN-BNT/PDMS composite film-based hybrid concept sheds light on energy harvesting devices.
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Flexible hybrid piezo/triboelectric energy harvester based on a lead-free BNT-BT-KNN ceramic-polymer composite film
(2024-12-01)
Panpho, Phakakorn
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Charoonsuk, Thitirat
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Vittayakorn, Naratip
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Bongkarn, Theerachai
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Sumang, Rattiphorn
Environment-friendly piezoelectric micro/nanogenerators have attracted tremendous attention due to the increasing demand for portable self-power devices. Here, the [(0.94−x)Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf>–0.06BaTiO<inf>3</inf>–xK<inf>0.5</inf>Na<inf>0.5</inf>NbO<inf>3</inf>; BNT-BT-xKNN] lead-free ceramic, at x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 mol%, was prepared via the solid-state method. The doping concentration x = 0.02 mol% shows the highest dielectric properties and the lowest dielectric loss. The active layer of the hybrid device is made by mixing BNT-BT-2KNN into the PDMS to form a series of polymer-ceramic composite films ranging from 7 to 19 wt% of BNT-BT-2KNN. The electrical response of the composite film is systematically studied with the addition of different weight percentages of the particles to the PDMS matrix. It was found that incorporating BNT-BT-2KNN at 11 wt% into the PDMS matrix exhibited the optimum harvesting performance, resulting in an output voltage and current density of about 30 V and 0.28 μA/cm2, respectively. The hybridized PENG and TENG devices could operate in a long-term cyclic mode, charge the capacitor for energy storage, and also light up LEDs. This research proposed a simple device fabrication and provided a guideline for the development of high-performance microgenerators, which is crucial for device development and practical use in the future.
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Tribovoltaic performance of the Schottky contact between metal and PZT ceramic
(2024-12-01)
Sriphan, Saichon
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Worathat, Supakarn
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Pakawanit, Phakkhananan
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Hajra, Sugato
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Kim, Hoe Joon
The sliding contact between a metal or semiconductor with another semiconductor can lead to a new charge generation mechanism known as the tribovoltaic effect. This effect has several advantage over the more common triboelectric effect, such as a higher rate of charge transfer and the ability to produce a direct current (DC) output directly via the junction interface. During operation, the junction interface produces a built-in electric field. In this study, we investigate the tribovoltaic effect on sliding between copper and unpoled lead zirconate titanate (PZT) ceramic. It was found that the contact between the metal and semiconducting oxide ceramic leads to the Schottky junction effect, which can effectively drive frictionally excited charges to an external load. By increasing the applied stress to PZT, we observed different current-voltage characteristic curves. The proposed electronic band behavior determines the electrical output direction in the tribovoltaic nanogenerator (TVNG). This direction depends on the built-in electric fields formed at the junction. The performance of the TVNG was tested in both series and parallel connections, observing clearly improved electrical outputs for both. The proposed TVNG can efficiently power small electronic devices, such as LEDs, and charge capacitors in a short period of time. This work expands the understanding of unconventional transport mechanisms through the Schottky contact of PZT and metal, and provides fundamental knowledge for the future development of tribovoltaic devices.
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Exploring liquid-solid interface based triboelectrification, structures, and applications
(2024-12-01)
Kaja, Kushal Ruthvik
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Hajra, Sugato
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Panda, Swati
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Belal, Mohamed A.
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Pharino, Utchawadee
In recent years, there has been a quest to accelerate the search for efficient and sustainable energy harvesting technologies due to challenges from fossil fuel depletion and environmental concerns. There is also a continous demand for autonomous sensing in our growing connected world. The liquid-solid triboelectric nanogenerator (L-S TENG) has emerged as a viable alternative, notably for generating mechanical energy from water. Despite extensive study into liquid-solid contact electrification techniques, a significant need remains to improve energy harvesting efficiency in L-S TENG systems. This comprehensive analysis delves into recent advances in energy harvesting from water, with a particular emphasis on understanding the interaction dynamics between liquid-solid interfaces when using triboelectric nanogenerators for energy conversion. This review summarizes recent developments in the structural design and applications of liquid-solid triboelectrification, focusing on improving TENG output performance. In addition, new insights are provided on the potential impact and future technical hurdles facing L-S TENG technologies. By offering new insights into current knowledge and future research directions, this review aims to guide progress in the field of L-S TENG energy harvesting.
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The apparent PTCR effect in layered alkali titanates - A correlation between temperature dependent electrical properties and thermal analyses
(2024-12-01)
Pulphol, Phieraya
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Chaithaweep, Kanokwan
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Vittayakorn, Naratip
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Maluangnont, Tosapol
Adsorbed water promotes proton conduction in ceramics at ambient conditions prior to its evaporation, apparently leading to the positive temperature coefficient of resistivity (PTCR) effect. Using surface water-containing Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> (1.8 mol water/mol titanate) as an example, the static conductivity (at 50 °C) of ∼10−5 S cm−1 is one thousand times that at 200 °C due to the enhanced proton conduction. At 50–150 °C, the conductivity decreases by 4 orders of magnitude because water evaporation decreases the number of charge carriers. At 150–400 °C, the conduction in water-free Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> is thermal-activated with the apparent activation energy E<inf>a</inf> ∼58–72 kJ mol−1, depending on the formalisms. We show clearly that an endothermic DSC peak (water evaporation) in Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> coincides with all eight presentations of AC properties examined. Similar correlations are obtained from the TG/DTG curves in Cs<inf>2</inf>Ti<inf>5</inf>O<inf>11</inf>·H<inf>2</inf>O containing mostly intercalated water. The correlation between thermal analyses and AC properties points out that water molecules essentially contribute to the charge transport at ambient conditions of layered alkali titanates. This scenario might be potentially extended to other humidity-sensitive ceramics.
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Equivalent circuit model and simulation for dynamic sliding droplet-based triboelectric nanogenerators
(2024-11-01)
Sriphan, Saichon
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Pharino, Utchawadee
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Chaithaweep, Kanokwan
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Vittayakorn, Naratip
Recently, there has been an increase of attention to employing liquid-solid contact to harvest or sense energy from water flow. Water's considerable deformability, however, makes it challenging to investigate how water moves dynamically in relation to a water-based triboelectric nanogenerator's (TENG) output characteristic. There are a few studies examining the fundamental mechanism of a droplet-based energy generator (DEG). In addition, such an electrical model has been established based on the consideration of instantaneous output at a specific period in a saturated state. Here, we first propose the circuit model and governing equations for simulating the double-electrode DEG's electrical output, comprehensively covering the L-S contact's dynamic process. Four essential stages of charge generation of the DEG are considered in unsaturated and saturated stages. The proposed model is verified systematically with the experimental data. The relationship between structural parameters and output performance of the DEG, such as internal capacitance, residual charge, dielectric constant, droplet spreading size, and dielectric thickness, has emerged. In summary, our model effectively establishes theoretical guidance, which paves the way for high-performance supply and sensor applications based on the L-S interface.
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Enhancing Performance of Composite-Based Triboelectric Nanogenerators Through Laser Surface Patterning and Graphite Coating for Sustainable Energy Solutions
(2024-11-01)
Amorntep, Narong
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Siritaratiwat, Apirat
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Srichan, Chavis
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Sriphan, Saichon
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Wiangwiset, Thalerngsak
The performance of composite-based triboelectric nanogenerators (C–TENGs) was significantly enhanced through laser surface patterning and graphite coating. The laser etching process produced accurate and consistent patterns, increasing surface area and improving charge accumulation. SEM imagery confirmed the structural differences and enhanced surface properties of the laser-etched C–TENGs. Graphite fibers further augmented the contact surface area, enhancing charge accumulation and diffusion. Experimental results demonstrated that the optimized C–TENGs, especially those with line patterns and graphite coating, achieved a maximal 98.87 V open-circuit voltage (V<inf>OC</inf>) and a 0.10 µA/cm2 short-circuit current density (J<inf>SC</inf>) under a 20 N external force. Environmental tests revealed a slight decrease in performance with increased humidity, while long-term stability tests indicated consistent performance over three weeks. Practical application tests showed the potential of C–TENGs integrated into wearable devices, generating sufficient energy for low-power applications, thereby highlighting the promise of these devices for sustainable energy solutions.
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Sodium-Poor, Hydroxyl-Rich, Defective Na2Ti3O7 Prepared by γ-Irradiation and Its Enhanced Proton Conductivity
(2024-09-30)
Maluangnont, Tosapol
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Sangtawesin, Tanagorn
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Pulphol, Phieraya
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Khamman, Orawan
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Reunchan, Pakpoom
The use of γ-irradiation to tailor the physicochemical properties of materials is not widely applied to layered alkali metal oxides. Herein, we show that γ-irradiation (up to 400 kGy) of Na<inf>2</inf>Ti<inf>3</inf>O<inf>7</inf> leads to a sodium-poor, hydroxyl-rich analogue where the layered structure, plate-like morphology, and textural properties are preserved. The deintercalation of sodium ions modifies the Ti-O bond lengths and expands the unit cell; the latter is supported by density functional theory (DFT) calculations. 23Na solid-state NMR suggests the transport of the symmetric, 7-fold Na2 sites to an intermediate environment, which is closer to the asymmetric, 9-fold Na1 sites. An 8 wt % mass loss (1.4 mol water/mol titanate) is observed, indicating an increased concentration of protons/hydroxyls. These hydroxyl groups (i.e., lattice protons) possess higher thermal stability than solely surface-adsorbed ones in the nonirradiated sample. At 200-400 kGy, the proton conduction (50 °C and ∼70% RH) of ∼10-6 S·cm-1 is 1 order of magnitude larger than that in the nonirradiated sample; the relaxation time decreases from 30 to 2-6 μs with γ-irradiation. The γ-dose dependence of dielectric loss is also present and analyzed using the Jonscher universal power law, indicating the low-frequency dispersion behavior characteristics of high charge densities.

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