Wearable and implantable devices require conductive, stretchable and biocompatible materials. However, obtaining composites that simultaneously fulfil these requirements is challenging due to a ...trade-off between conductivity and stretchability. Here, we report on Ag-Au nanocomposites composed of ultralong gold-coated silver nanowires in an elastomeric block-copolymer matrix. Owing to the high aspect ratio and percolation network of the Ag-Au nanowires, the nanocomposites exhibit an optimized conductivity of 41,850 S cm
(maximum of 72,600 S cm
). Phase separation in the Ag-Au nanocomposite during the solvent-drying process generates a microstructure that yields an optimized stretchability of 266% (maximum of 840%). The thick gold sheath deposited on the silver nanowire surface prevents oxidation and silver ion leaching, making the composite biocompatible and highly conductive. Using the nanocomposite, we successfully fabricate wearable and implantable soft bioelectronic devices that can be conformally integrated with human skin and swine heart for continuous electrophysiological recording, and electrical and thermal stimulation.
Biomolecular piezoelectric materials are considered a strong candidate material for biomedical applications due to their robust piezoelectricity, biocompatibility, and low dielectric property. The ...electric field has been found to affect tissue development and regeneration, and the piezoelectric properties of biological materials in the human body are known to provide electric fields by pressure. Therefore, great attention has been paid to the understanding of piezoelectricity in biological tissues and its building blocks. The aim herein is to describe the principle of piezoelectricity in biological materials from the very basic building blocks (i.e., amino acids, peptides, proteins, etc.) to highly organized tissues (i.e., bones, skin, etc.). Research progress on the piezoelectricity within various biological materials is summarized, including amino acids, peptides, proteins, and tissues. The mechanisms and origin of piezoelectricity within various biological materials are also covered.
The piezoelectricity of the various elements constituting the human body has attracted intensive attention, due to the strong piezoelectricity, biocompatibility, low dielectric, and tissue regeneration effects. Research progress in the various biological piezoelectric materials from the basic building blocks to organized tissues are summarized. The mechanisms and origins of piezoelectricity are discussed, and challenges and perspectives for developing biological piezoelectric materials are presented.
In this work, a sulfur (S) vacancy passivated monolayer MoS2 piezoelectric nanogenerator (PNG) is demonstrated, and its properties before and after S treatment are compared to investigate the effect ...of passivating S vacancy. The S vacancies are effectively passivated by using the S treatment process on the pristine MoS2 surface. The S vacancy site has a tendency to covalently bond with S functional groups; therefore, by capturing free electrons, a S atom will form a chemisorbed bond with the S vacancy site of MoS2. S treatment reduces the charge‐carrier density of the monolayer MoS2 surface, thus the screening effect of piezoelectric polarization charges by free carrier is significantly prevented. As a result, the output peak current and voltage of the S‐treated monolayer MoS2 nanosheet PNG are increased by more than 3 times (100 pA) and 2 times (22 mV), respectively. Further, the S treatment increases the maximum power by almost 10 times. The results suggest that S treatment can reduce free‐charge carrier by sulfur S passivation and efficiently prevent the screening effect. Thus, the piezoelectric output peaks of current, voltage, and maximum power are dramatically increased, as compared with the pristine MoS2.
Piezoelectricity of sulfur vacancy passivated MoS2 nanosheets is much higher than that of pristine MoS2 nanosheets. Sulfur vacancies can be filled through a sulfur treatment and the resulting output power of the device generates a 10‐times higher power. This result offers a new approach to realize a MoS2 nanosheet‐based high‐performance piezoelectric nanogenerator for self‐powered wearable electronics.
Paper‐based electronics has attracted growing interest owing to many advantages of papers including low‐cost, abundance, flexibility, biocompatibility, and environmental friendliness. Despite recent ...progress in paper electronics, however, development of a high‐performance paper‐based triboelectric nanogenerator (TENG), which is a power‐generating device that converts mechanical energy into electric energy by coupling triboelectrification and electrostatic induction, remains a challenge mainly due to weak electron‐donating tendency of cellulose‐based papers. In this work, highly conductive ferroelectric cellulose composite papers containing silver nanowires and BaTiO3 nanoparticles are fabricated, and their successful application for realizing a large‐area TENG with enhanced electrical output performance is demonstrated. It is found that triboelectric charge generation on the ferroelectric cellulose composite paper can be promoted by simple poling treatment, which significantly enhances TENG performance. The ferroelectric cellulose composite paper–based TENG exhibits an electrical output performance that surpasses those of aluminum‐based and pristine cellulose–based TENGs by more than two times, as well as outstanding output stability without a noticeable degradation in performance during 10 000 cycles of a repeated pushing test. The work demonstrates the great potential of multifunctional cellulose‐based papers for TENG and other self‐powered electronic applications.
Highly conductive ferroelectric cellulose composite papers containing silver nanowires and BaTiO3 nanoparticles are prepared to fabricate high‐performance paper‐based triboelectric nanogenerators. Poling treatment of this ferroelectric paper leads to dipole alignment, which promotes triboelectric charge generation on the paper and thus enables enhanced electrical output performance.
Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal‐boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated ...monolayer MoS2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal‐stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)‐grown WSe2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD‐grown WSe2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe2 for which the device performance becomes degraded above a strain of 0.63%.
WSe2 bilayers with turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a WSe2 monolayer. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources.
The preparation of ferroelectric polymer–metallic nanowire composite nanofiber triboelectric layers is described for use in high‐performance triboelectric nanogenerators (TENGs). The electrospun ...polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite and nylon nanofibers are utilized in the TENGs as the top and bottom triboelectric layers, respectively. The electrospinning process facilitates uniaxial stretching of the polymer chains, which enhances the formation of the highly oriented crystalline β‐phase that forms the most polar crystalline phase of PVDF. The addition of AgNWs further promotes the β‐phase crystal formation by introducing electrostatic interactions between the surface charges of the nanowires and the dipoles of the PVDF chains. The extent of β‐phase formation and the resulting variations in the surface charge potential upon the addition of nanowires are systematically analyzed using X‐ray diffraction (XRD) and Kelvin probe force microscopy techniques. The ability of trapping the induced tribocharges increases upon the addition of nanowires to the PVDF matrix. The enhanced surface charge potential and the charge trapping capabilities of the PVDF–AgNW composite nanofibers significantly enhance the TENG output performances. Finally, the mechanical stability of the electrospun nanofibers is dramatically enhanced while maintaining the TENG performances by applying thermal welding near the melting temperature of PVDF.
High‐performance triboelectric nanogenerators (TENG) are successfully demonstrated using electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite nanofibers. It is found that an electrospinning process and the addition of AgNWs to the PVDF promote the effective formation of the polar crystalline β‐phase. The enhanced surface charge potential and charge trapping properties of the PVDF–AgNW composite nanofibers significantly enhance the TENG performances.
Nanomaterials with antioxidant properties are promising for treating reactive oxygen species (ROS)‐related diseases. However, maintaining efficacy at low doses to minimize toxicity is a critical for ...clinical applications. Tuning the surface strain of metallic nanoparticles can enhance catalytic reactivity, which has rarely been demonstrated in metal oxide nanomaterials. Here, it is shown that inducing surface strains of CeO2/Mn3O4 nanocrystals produces highly catalytic antioxidants that can protect tissue‐resident stem cells from irradiation‐induced ROS damage. Manganese ions deposited on the surface of cerium oxide (CeO2) nanocrystals form strained layers of manganese oxide (Mn3O4) islands, increasing the number of oxygen vacancies. CeO2/Mn3O4 nanocrystals show better catalytic activity than CeO2 or Mn3O4 alone and can protect the regenerative capabilities of intestinal stem cells in an organoid model after a lethal dose of irradiation. A small amount of the nanocrystals prevents acute radiation syndrome and increases the survival rate of mice treated with a lethal dose of total body irradiation.
Inducing surface strains of CeO2/Mn3O4 nanocrystals produces highly catalytic antioxidants that are powerful enough to protect intestinal stem cells from irradiation‐induced reactive oxygen species damage. Only a small dose of the CeO2/Mn3O4 nanocrystals prevents acute radiation syndrome in a human intestinal organoid model and increases survival rate of mice treated with a lethal dose of total body irradiation.
Inspired by treefrog's toe pads that show superior frictional properties, herein, an industrially compatible approach is reported to make an efficient dielectric tribosurface design using ...customizable nonclose‐packed microbead arrays, mimicking the friction pads of treefrogs, in order to significantly enhance electrification performance and reliability of triboelectric nanogenerator (TENG). The approach involves using an engineering polymer to prepare a highly ordered large‐area concave film, and subsequently the molding of a convex patterned triboreplica in which the concave film is exploited as a reusable master mold. A nature‐inspired TENG based on the patterned polydimethylsiloxane (PDMS) paired with flat aluminum (Al) can generate a relatively high power density of 8.1 W m−2 even if a very small force of ≈6.5 N is applied. Moreover, the convex patterned PDMS‐based TENG possesses exceptional durability and reliability over 25 000 cycles of contact–separation. Considering the significant improvements in power generation of TENG; particularly at very small force, together with cost‐effectiveness and possibility of mass production, the present methodology may pave the way for large‐scale blue energy harvesting and commercialization of TENGs for many practical applications.
Treefrog toe pad‐inspired micropattern arrarys of the tribo‐dielectric surface for the high‐power triboelectric nanogenerator(TENG) demonstrates an output voltage of 490 V and current density of 24.4 µA cm−2, with an instantaneous power density of 23.9 Wm−2 under a compressive force of 38 N. This study also guides a rational design for the patterned surfaces in order to produce a high‐performance reliable TENG.
Recently, research on energy harvesting has attracted great attention as a solution to energy depletion and environmental problems due to the use of fossil fuels such as coal, natural gas, and oil. ...To be precise, harvesting technology converts the energy sources around us such as solar, heat, and mechanical energy into electrical energy. It has the advantage of being able to supply and sustain energy on a permanent basis, rather than being non-renewable, and it is also eco-friendly. Among the various energy harvesting techniques, nanogenerators based on piezoelectric and triboelectric phenomena can generate electrical energy based on mechanical energy sources, which are usually ubiquitous, there are no restrictions due to weather, time, or space, and this technology is also user-friendly. Recently, two-dimensional (2D) materials have been chosen for implementing piezo/triboelectric nanogenerators. The 2D materials have transparency, flexibility, and a high surface-to-volume ratio. Owing to the very low thickness of the atomic unit, a stacking structure using 2D materials can be also made to form a very thin device, which is applicable for insertion into the body or wearable electronic devices. In this review, we summarize the characteristics and research results on piezo/triboelectric energy harvesters based on 2D layered structure materials.
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•The characteristics of 2D materials are transparency, flexibility, and high surface-to-volume ratio.•With these advantages, 2D materials with piezo/triboelectric potential can be applied as various electronic devices.•We summarize the research results on piezo/triboelectric energy harvester based on 2D layered structure materials.
Poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)), as a ferroelectric polymer, offers great promise for energy harvesting for flexible and wearable applications. Here, this paper shows that ...the choice of solvent used to dissolve the polymer significantly influences its properties in terms of energy harvesting. Indeed, the P(VDF‐TrFE) prepared using a high dipole moment solvent has higher piezoelectric and pyroelectric coefficients and triboelectric property. Such improvements are the result of higher crystallinity and better dipole alignment of the polymer prepared using a higher dipole moment solvent. Finite element method simulations confirm that the higher dipole moment results in higher piezoelectric, pyroelectric, and triboelectric potential distributions. Furthermore, P(VDF‐TrFE)‐based piezoelectric, pyroelectric, and triboelectric nanogenerators (NGs) experimentally validate that the higher dipole moment solvent significantly enhances the power output performance of the NGs; the improvement is about 24% and 82% in output voltage and current, respectively, for piezoelectric NG; about 40% and 35% in output voltage and current, respectively, for pyroelectric NG; and about 65% and 75% in output voltage and current for triboelectric NG. In brief, the approach of using a high dipole moment solvent is very promising for high output P(VDF‐TrFE)‐based wearable NGs.
High‐performance piezoelectric‐, pyroelectric‐, and triboelectric‐nanogenerators‐based P(VDF‐TrFE) with controlled crystallinity and dipole alignment have been successfully demonstrated using a higher dipole moment solvent for higher crystallinity and better dipole alignment. Therefore, a higher dipole moment solvent enhances the piezoelectric coefficient, pyroelectric coefficient, and triboelectric property of P(VDF‐TrFE) and the power output performance of P(VDF‐TrFE)‐based piezoelectric, pyroelectric, and triboelectric nanogenerators.
