An Integrated Power Pack of Dye-Sensitized Solar Cell and Li Battery Based on Double-Sided TiO₂ Nanotube Arrays

We present a new approach to fabricate an integrated power pack by hybridizing energy harvest and storage processes. This power pack incorporates a series-wound dye-sensitized solar cell (DSSC) and a lithium ion battery (LIB) on the same Ti foil that has double-sided TiO₂ nanotube (NTs) arrays. The solar cell part is made of two different cosensitized tandem solar cells based on TiO₂ nanorod arrays (NRs) and NTs, respectively, which provide an open-circuit voltage of 3.39 V and a short-circuit current density of 1.01 mA/cm². The power pack can be charged to about 3 V in about 8 min, and the discharge capacity is about 38.89 μAh under the discharge density of 100 μA. The total energy conversion and storage efficiency for this system is 0.82%. Such an integrated power pack could serve as a power source for mobile electronics

Piezotronic Effect on the Output Voltage of P3HT/ZnO Micro/Nanowire Heterojunction Solar Cells

We report the first observation of piezotronic effect on the output voltage of a flexible heterojunction solar cell. The solar cell was fabricated by contacting poly(3-hexylthiophene) (P3HT) with one end of a ZnO micro/nanowire to form a p–n heterojunction on a flexible polystyrene (PS) substrate. The open-circuit voltage <i>V</i>_oc of the solar cell was characterized by tuning the strain-induced polarization charges at the interface between ZnO and P3HT. The experimental data were understood based on the modification of the band structure at the p–n junction by the piezopotential, which is referred as a result of the piezotronic effect. This study not only provides an in-depth understanding about the effect but also is useful for maximizing the output of a solar cell using wurtzite structured materials

Piezo-phototronic Effect Enhanced Visible/UV Photodetector of a Carbon-Fiber/ZnO-CdS Double-Shell Microwire

A branched ZnO-CdS double-shell NW array on the surface of a carbon fiber (CF/ZnO-CdS) was successfully synthesized <i>via</i> a facile two-step hydrothermal method. Based on a single CF/ZnO-CdS wire on a polymer substrate, a flexible photodetector was fabricated, which exhibited ultrahigh photon responsivity under illuminations of blue light (1.11 × 10⁵ A/W, 8.99 × 10^–8 W/cm², 480 nm), green light (3.83 × 10⁴ A/W, 4.48 × 10^–8 W/cm², 548 nm), and UV light (1.94 × 10⁵ A/W, 1.59 × 10^–8 W/cm², 372 nm), respectively. The responsivity of this broadband photon sensor was enhanced further by as much as 60% when the device was subjected to a −0.38% compressive strain. This is because the strain induced a piezopotential in ZnO, which tunes the barrier height at the ZnO–CdS heterojunction interface, leading to an optimized optoelectronic performance. This work demonstrates a promising application of piezo-phototronic effect in nanoheterojunction array based photon detectors

Rectangular Bunched Rutile TiO₂ Nanorod Arrays Grown on Carbon Fiber for Dye-Sensitized Solar Cells

Because of their special application in photovoltaics, the growth of one-dimensional single-crystalline TiO₂ nanostructures on a flexible substrate is receiving intensive attention. Here we present a study of rectangular bunched TiO₂ nanorod (NR) arrays grown on carbon fibers (CFs) from titanium by a “dissolve and grow” method. After a corrosion process in a strong acid solution, every single nanorod is etched into a number of small nanowires. Tube-shaped dye-sensitized solar cells are fabricated by using etched TiO₂ NRs-coated CFs as the photoanode. An absolute energy conversion efficiency of 1.28% has been demonstrated under 100 mW cm^–2 AM 1.5 illumination. This work demonstrates an innovative method for growing bunched TiO₂ NRs on flexible substrates that can be applied in flexible devices for energy harvesting and storage

Triboelectric-Generator-Driven Pulse Electrodeposition for Micropatterning

By converting ambient energy into electricity, energy harvesting is capable of at least offsetting, or even replacing, the reliance of small portable electronics on traditional power supplies, such as batteries. Here we demonstrate a novel and simple generator with extremely low cost for efficiently harvesting mechanical energy that is typically present in the form of vibrations and random displacements/deformation. Owing to the coupling of contact charging and electrostatic induction, electric generation was achieved with a cycled process of contact and separation between two polymer films. A detailed theory is developed for understanding the proposed mechanism. The instantaneous electric power density reached as high as 31.2 mW/cm³ at a maximum open circuit voltage of 110 V. Furthermore, the generator was successfully used without electric storage as a direct power source for pulse electrodeposition (PED) of micro/nanocrystalline silver structure. The cathodic current efficiency reached up to 86.6%. Not only does this work present a new type of generator that is featured by simple fabrication, large electric output, excellent robustness, and extremely low cost, but also extends the application of energy-harvesting technology to the field of electrochemistry with further utilizations including, but not limited to, pollutant degradation, corrosion protection, and water splitting

Tough, Freeze-Resistant, Pressure-Response Gel Polymer Electrolytes with Redox Pairs for Flexible Supercapacitors

Gel polymer electrolytes are an indispensable part of flexible supercapacitors, since their various characteristics determine the device performance. Here, a composite gel electrolyte (FLPS) mainly consisting of polyvinyl alcohol (PVA), sodium alginate (SA), K3Fe(CN)6/K4Fe(CN)6, and LiCl is rationally designed, in which PVA and SA form a robust three-dimensional network, the redox pair of K3Fe(CN)6/K4Fe(CN)6 serves as a cross-linking agent with SA and even donates the oxidation–reduction reaction from the Fe3+/Fe2+ couple with additional capacitance for the device, and LiCl functions as an ion carrier and a water-retaining salt to improve the long-term stability of FLPS. Thus, the FLPS-based supercapacitor exhibits superior electrochemical characteristics, displaying impressive pseudocapacitance across all current densities and excellent cycling stability (∼99.07% of capacitance retention after 10,000 cycles). Moreover, the FLPS-based supercapacitor demonstrates great low-temperature working ability and pressure responsiveness, suggesting its freeze-resistance, flexibility, and pressure sensing potential. This work provides a promising strategy for preparing tough gel polymer electrolytes with both ion transfer and charge storage ability

Pyroelectric Nanogenerators for Harvesting Thermoelectric Energy

Harvesting thermoelectric energy mainly relies on the Seebeck effect that utilizes a temperature difference between two ends of the device for driving the diffusion of charge carriers. However, in an environment that the temperature is spatially uniform without a gradient, the pyroelectric effect has to be the choice, which is based on the spontaneous polarization in certain anisotropic solids due to a time-dependent temperature variation. Using this effect, we experimentally demonstrate the first application of pyroelectric ZnO nanowire arrays for converting heat energy into electricity. The coupling of the pyroelectric and semiconducting properties in ZnO creates a polarization electric field and charge separation along the ZnO nanowire as a result of the time-dependent change in temperature. The fabricated nanogenerator has a good stability, and the characteristic coefficient of heat flow conversion into electricity is estimated to be ∼0.05–0.08 Vm²/W. Our study has the potential of using pyroelectric nanowires to convert wasted energy into electricity for powering nanodevices

An All-Protein Multisensory Highly Bionic Skin

To achieve a highly realistic robot, closely mimicking human skin in terms of materials and functionality is essential. This paper presents an all-protein silk fibroin bionic skin (SFBS) that emulates both fast-adapting (FA) and slow-adapting (SA) receptors. The mechanically different silk film and hydrogel, which exhibited skin-like properties, such as stretchability (>140%), elasticity, low modulus (<10 kPa), biocompatibility, and degradability, were prepared through mesoscopic reconstruction engineering to mimic the epidermis and dermis. Our SFBS, incorporating SA and FA sensors, demonstrated a highly sensitive (1.083 kPa–1) static pressure sensing performance (in vitro and in vivo), showed the ability to sense high-frequency vibrations (50–400 Hz), could discriminate materials and sliding, and could even identify the fine morphological differences between objects. As proof of concept, an SFBS-integrated rehabilitation glove was synthesized, which could help stroke patients regain sensory feedback. In conclusion, this work provides a practical approach for developing skin equivalents, prostheses, and smart robots

An All-Protein Multisensory Highly Bionic Skin

To achieve a highly realistic robot, closely mimicking human skin in terms of materials and functionality is essential. This paper presents an all-protein silk fibroin bionic skin (SFBS) that emulates both fast-adapting (FA) and slow-adapting (SA) receptors. The mechanically different silk film and hydrogel, which exhibited skin-like properties, such as stretchability (>140%), elasticity, low modulus (<10 kPa), biocompatibility, and degradability, were prepared through mesoscopic reconstruction engineering to mimic the epidermis and dermis. Our SFBS, incorporating SA and FA sensors, demonstrated a highly sensitive (1.083 kPa–1) static pressure sensing performance (in vitro and in vivo), showed the ability to sense high-frequency vibrations (50–400 Hz), could discriminate materials and sliding, and could even identify the fine morphological differences between objects. As proof of concept, an SFBS-integrated rehabilitation glove was synthesized, which could help stroke patients regain sensory feedback. In conclusion, this work provides a practical approach for developing skin equivalents, prostheses, and smart robots

An All-Protein Multisensory Highly Bionic Skin

To achieve a highly realistic robot, closely mimicking human skin in terms of materials and functionality is essential. This paper presents an all-protein silk fibroin bionic skin (SFBS) that emulates both fast-adapting (FA) and slow-adapting (SA) receptors. The mechanically different silk film and hydrogel, which exhibited skin-like properties, such as stretchability (>140%), elasticity, low modulus (<10 kPa), biocompatibility, and degradability, were prepared through mesoscopic reconstruction engineering to mimic the epidermis and dermis. Our SFBS, incorporating SA and FA sensors, demonstrated a highly sensitive (1.083 kPa–1) static pressure sensing performance (in vitro and in vivo), showed the ability to sense high-frequency vibrations (50–400 Hz), could discriminate materials and sliding, and could even identify the fine morphological differences between objects. As proof of concept, an SFBS-integrated rehabilitation glove was synthesized, which could help stroke patients regain sensory feedback. In conclusion, this work provides a practical approach for developing skin equivalents, prostheses, and smart robots