In spite of the recent successful demonstrations of flexible and transparent film heaters, most heaters with high optical transmittance and low applied direct current （DC） voltage are silver nanowire ...（Ag NW）-based or silver grid-based. In this study, flexible and stretchable copper nanowire （Cu NW）-based transparent film heaters were fabricated through a solution-based process, in which a thin layer of hydrophobic polymers was encapsulated on the Cu NW films. The thin polymer layer protected the films from oxidation under harsh testing conditions, i.e., high temperature, high humidity, and acidic and alkaline environments. The films exhibited remarkable performance, a wide operating temperature range （up to 150 ℃）, and a high heating rate （14 ℃/s）. Defrosting and wearable thermotherapy demonstrations of the Cu NW film heaters were carried out to investigate their practicality. The Cu NW-based film heaters have potential as reliable and low-cost film heaters.
Three etchants are used to synthesize three different Ti3C2Tx (MXene) samples. The difference in chemical components, morphology and surface terminations of Ti3C2Tx and their influences on the ...conductivity, stability and flexibility are comprehensively analyzed. The underlying mechanism is investigated simultaneously. Besides, favorable annealing treatments and storage conditions are also proposed to optimize the properties of Ti3C2Tx.
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•Three typical etchants HF, LiF/HCl, TMAOH are used to synthesize three different Ti3C2Tx (MXene) samples.•The difference in chemical components, morphology and surface terminations of Ti3C2Tx are comprehensively analyzed.•Favorable annealing treatments and storage conditions are also proposed to optimize the properties of Ti3C2Tx.
Two-dimensional transition metal carbides or/and nitrides (MXenes) exhibit great development prospects in energy storage, catalysis, sensing and other fields due to their good properties. However, MXenes obtained from different etching conditions show great discrepancy on their electrical and mechanical properties, which will affect their applications to a certain degree. Unfortunately, few reports have systematically investigated such discrepancy and the underlying mechanism. Herein, three etchants and corresponding subsequent operations were used to synthesize three different Ti3C2Tx (MXene) samples. The difference in chemical components, morphology and surface terminations of Ti3C2Tx and their influences on the conductivity, stability and flexibility were comprehensively analyzed. The underlying mechanism has been investigated simultaneously. Based on this, favorable annealing treatments and storage conditions are also proposed to optimize the properties of Ti3C2Tx, which is believed of great meaning to the practical applications of Ti3C2Tx.
Copper nanowires (Cu NWs) hold great promise for the fabrication of low-cost transparent electrodes. However, the instability of Cu NWs has limited their application into commercial devices. Herein, ...CVD-grown graphene is transferred onto Cu NW films and the stability of the hybrid films over long time scale under different conditions is investigated systematically. The results reveal that the graphene-Cu NW films can maintain their efficacy (
R
/
R
0
< 2) after 180 days of exposure in an ambient atmosphere. Furthermore, a two-step oxidation kinetic mechanism of Cu NWs can be proposed by using Raman and X-Ray photoelectron spectroscopy. The protecting mechanism of graphene on Cu NW films is disclosed to preventing the oxygen species permeation, decelerating the oxidation from Cu to Cu
2
O and hindering the oxidation of Cu
2
O to CuO. These results are of referring significance to make metal nanowire based transparent electrodes with both high optical-electrical performance and excellent stability.
Cu nanowire oxidation kinetics is proposed, and the protecting mechanism of transferred graphene on Cu nanowires is proved by stability investigation.
Copper nanowires （Cu NWs） have attracted increasing attention as building blocks for electronics due to their outstanding electrical properties and low cost. However, organic residues and oxide ...layers ubiquitously existing on the surface of Cu NWs impede good inter-wire contact. Commonly used methods such as thermal annealing and acid treatment often lead to nanowire damage. Herein, hydrogen plasma treatment at room temperature has been demonstrated to be effective for simultaneous surface cleaning and selective welding of Cu NWs at junctions. Transparent electrodes with excellent optical-electrical performance （19 ff）-sq-1 @ 90% T） and enhanced stability have been fabricated and integrated into organic solar cells. Besides, Cu NW conductors with superior stretchability and cycling stability under stretching speeds of up to 400 mm-min-＇ can also be produced by the nanowelding process, and the feasibility of their application in stretchable LED circuits has been demonstrated.
Bioelectric electrodes with low modulus and high adhesion have been intensively pursued, as they afford conformal and strong bonding at skin‐electrode interface to improve the fidelity and stability ...of electrophysiological signals. However, during detachment, tough adhesion can cause pain or skin allergy; worse still, the soft electrodes can suffer damage due to excessive stretch/torsion, hampering long‐term, dynamic, and multiple uses. Herein, a bioelectric electrode is proposed by transferring silver nanowires (AgNWs) network to the surface of bistable adhesive polymer (BAP). The phase transition temperature of BAP is tuned to be slightly below skin temperature at 30 °C. Triggered by skin heat, the BAP electrode achieves low modulus and high adhesion within seconds, allowing robust skin‐electrode interface under dry, wet, and body‐moving conditions. Ice bag treatment can dramatically stiffen the electrode and reduce the adhesion, which allows painless detachment and avoids electrode damage. Meanwhile, the AgNWs network with biaxial wrinkled microstructure remarkably promotes the electro‐mechanical stability of the BAP electrode. The BAP electrode successfully combines long‐term (7 days) and dynamic (body movements, sweat, underwater) stability, reusability (at least ten times), and minimized skin irritation during electrophysiological monitoring. The high signal‐to‐noise ratio and dynamic stability are demonstrated in the application of piano‐playing training.
A bioelectric electrode is developed by incorporating a temperature‐sensitive phase‐transition polymer and a biaxially pre‐strained AgNWs percolation network. The bioelectric electrode exhibits a quick and dramatic stiffness/adhesion switch around skin temperature, which enables stable electrophysiological monitoring in long‐term and dynamic states, and allows painless and non‐destructive detachment and reusability.
Graphene transfer is a critical process in the journey from CVD-grown graphene to device application. The current transfer techniques use a chemical-etching method to oxidize the metal catalyst, ...which is heavily time-consuming and involves a high material cost. In this study, a highly efficient symmetrical bi-electrode technique has been developed to simultaneously delaminate the CVD-grown graphene from the metal catalyst at both the anode and cathode of the electrolytic cell. Raman spectra, UV-visible transmittance, and four-probe measurements confirm that this transfer process is nondestructive and can produce similar electrical properties to those produced by the conventional metal-etching transfer method. This bi-electrode transfer technique possesses the advantages of high efficiency, recyclable use of metal catalyst, and high electrical conductivity, and it can be potentially applied for industrial applications.
A high sensitivity and large stretchability are desirable for strain sensors in wearable applications. However, these two performance indicators are contradictory, since the former requires a ...conspicuous structural change under a tiny strain, whereas the latter demands morphological integrity upon a large deformation. Developing strain sensors with both a high sensitivity (gauge factor (GF) > 100) and a broad strain range (>50%) is a considerable challenge. Herein, a unique Ti3C2Tx MXene nanoparticle–nanosheet hybrid network is constructed. The migration of nanoparticles leads to a large resistance variation while the wrapping of nanosheet bridges the detached nanoparticles to maintain the connectivity of the conductive pathways in a large strain region. The synergetic motion of nanoparticles and nanosheets endows the hybrid network with splendid electrical–mechanical performance, which is reflected in its high sensitivity (GF > 178.4) over the entire broad range (53%), the super low detection limit (0.025%), and a good cycling durability (over 5000 cycles). Such high performance endows the strain sensor with the capability for full‐range human motion detection.
A strain sensor based on a Ti3C2Tx nanoparticle‐nanosheet hybrid network exhibits high sensitivity over the entire broad range due to the synergetic motion of nanoparticles and nanosheets and a constrained microcrack propagation mechanism. The migration of nanoparticles leads to a large resistance variation while the wrapping of the nanosheets bridges the nanoparticles and maintains the connectivity of the conductive pathways.
Abstract
A high sensitivity and large stretchability are desirable for strain sensors in wearable applications. However, these two performance indicators are contradictory, since the former requires ...a conspicuous structural change under a tiny strain, whereas the latter demands morphological integrity upon a large deformation. Developing strain sensors with both a high sensitivity (gauge factor (GF) > 100) and a broad strain range (>50%) is a considerable challenge. Herein, a unique Ti
3
C
2
T
x
MXene nanoparticle–nanosheet hybrid network is constructed. The migration of nanoparticles leads to a large resistance variation while the wrapping of nanosheet bridges the detached nanoparticles to maintain the connectivity of the conductive pathways in a large strain region. The synergetic motion of nanoparticles and nanosheets endows the hybrid network with splendid electrical–mechanical performance, which is reflected in its high sensitivity (GF > 178.4) over the entire broad range (53%), the super low detection limit (0.025%), and a good cycling durability (over 5000 cycles). Such high performance endows the strain sensor with the capability for full‐range human motion detection.
Recent years have witnessed significant development of flexible strain sensors in a variety of fields. Nevertheless, the challenge of integrating a broad sensing range (>50%) with high sensitivity ...gauge factor (GF) value > 100 over the entire sensing strain in one single flexible strain sensor still exists. Herein, we prepared a flexible strain sensor based on braided graphene belts (BGBs) and dragon skin. Such a BGB strain sensor exhibits an integration of a wide sensing range (up to 55.55%) and high sensitivity (GF value > 175.16 through the entire working range). Besides, this BGB strain sensor also demonstrates a minute monitoring limit (0.01%), low hysteresis and overshoot behaviors, and reliable cycling repeatability (>6000 cycles). The SEM microscopy observations reveal that the skew angle and intersection regions of graphene belts are mainly responsible for the desirable sensing performance. Finally, the successful detection of full-range human motions, from subtle actions to vigorously joint-related movements, reflects great potential of the BGB strain sensor in the application of wearable instruments.
A Cu nanowire （NW）/cuprous oxide （Cu2O）-based semiconductor-liquid junction solar cell with a greatly enhanced efficiency and reduced cost was assembled. The Cu NWs function as a transparent ...electrode as well as part of the Cu NWs/ Cu2O coaxial structures, which remarkably benefit the charge separation. The best solar cell reached a conversion efficiency as high as 1.92% under a simulated AM1.5G illumination, which is 106 times higher than that of cells based on fluorine-doped tin oxide and Cu2O.
