Stretchable,Transparent,and Ultra-Broadband Terahertz Shielding Thin Films Based on Wrinkled MXene Architectures

With the increasing demand for terahertz(THz)technology in security inspection,medical imaging,and flexible electronics,there is a significant need for stretchable and transparent THz electromagnetic interference(EMI)shielding materials.Existing EMI shielding materials,like opaque metals and carbon-based films,face challenges in achieving both high transparency and high shielding efficiency(SE).Here,a wrinkled structure strategy was proposed to construct ultra-thin,stretchable,and transparent terahertz shielding MXene films,which possesses both isotropous wrinkles(height about 50 nm)and periodic wrinkles(height about 500 nm).Compared to flat film,the wrinkled MXene film(8 nm)demonstrates a remarkable 36.5%increase in SE within the THz band.The wrinkled MXene film exhibits an EMI SE of 21.1 dB at the thickness of 100 nm,and an average EMI SE/t of 700 dBμm^(−1)over the 0.1-10 THz.Theoretical calculations suggest that the wrinkled structure enhances the film’s conductivity and surface plasmon resonances,resulting in an improved THz wave absorption.Additionally,the wrinkled structure enhances the MXene films’stretchability and stability.After bending and stretching(at 30%strain)cycles,the average THz transmittance of the wrinkled film is only 0.5%and 2.4%,respectively.The outstanding performances of the wrinkled MXene film make it a promising THz electromagnetic shielding materials for future smart windows and wearable electronics.

Controlled fabrication of nanoscale wrinkle structure by fluorocarbon plasma for highly transparent triboelectric nanogenerator

In this paper,we report a novel nanoscale wrinkle-structure fabrication process using fluorocarbon plasma on poly(dimethylsiloxane)(PDMS)and Solaris membranes.Wrinkles with wavelengths of hundreds of nanometers were obtained on these two materials,showing that the fabrication process was universally applicable.By varying the plasma-treating time,the wavelength of the wrinkle structure could be controlled.Highly transparent membranes with wrinkle patterns were obtained when the plasmatreating time was o125 s.The transmittances of these membranes were 490%in the visible region,making it difficult to distinguish them from a flat membrane.The deposited fluorocarbon polymer also dramatically reduced the surface energy,which allowed us to replicate the wrinkle pattern with high precision onto other membranes without any surfactant coating.The combined advantages of high electron affinity and high transparency enabled the fabricated membrane to improve the performance of a triboelectric nanogenerator.This nanoscale,single-step,and universal wrinkle-pattern fabrication process,with the functionality of high transparency and ultra-low surface energy,shows an attractive potential for future applications in microand nanodevices,especially in transparent energy harvesters.

Wrinkle-crease interaction behavior simulation of a rectangular membrane under shearing

Wrinkling analysis of a rectangular membrane with a single crease under shearing is performed to understand the wrinkle-crease interaction behaviors. The crease is considered by introducing the residual stresses from creasing and the effective modulus into the baseline configuration with assumed circular cross-sectional crease geometry. The wrinkling analysis of the creased membrane is then performed by using the direct perturb-force （DP） simulation technique which is based on our modified displacement components （MDC） method. Results reveal that the crease may influence the stress transfer path in the membrane and further change the wrinkling direction. The crease appears to improve the bending stiffness of the membrane which has an effective resistance on the wrinkling evolution. The effects of the crease orientation on wrinkle-crease interaction are studied toward the end of this paper. The results show that the wrinkling amplitude, wavelength, and direction increase as the crease orientation increases, and the wrinkling number decreases with the increasing crease orientation. These results will be of great benefit to the analysis and the control of the wrinkles in the membrane structures.

Experiment and evaluation of wrinkling strain in a corner tensioned square membrane

Prediction of wrinkling characteristics is strongly correlated with the strain perpendicular to wrinkling direc- tion. In this paper, the strain field of wrinkled membrane is tested by VIC-3D system based on the digital image correlation technique. Experimental results are validated by the tension wrinkling simulation. The experimental strain perpendicular to wrinkling direction is analyzed in depth. The wrinkling strain of a square wrinkled membrane under corner tension is extracted from experimental strain perpendicular to wrinkling direction. A quantitative characterization format of the experimental wrinkling strain is proposed. A modified prediction method of wrinkling amplitude is presented based on the experimental wrinkling strain. The re- sults show that the precision of modified prediction model has improved 13.2% compared with the classical prediction model. The results reveal that the modified model can give an accurate prediction of the wrinkling amplitude.

A study on wrinkling characteristics and dynamic mechanical behavior of membrane

An eigenvalue method considering the membrane vibration of wrinkling out-of-plane deformation is introduced, and the stress distributing rule in membrane wrinkled area is analyzed. A dynamic analytical model of rectangular shear wrinkled membrane and its numerical analysis approach are also developed. Results indicate that the stress in wrinkled area is not uniform, i.e. it is larger in wrinkling wave peaks along wrinkles and two ends of wrinkle in vertical direction. Vibration modes of wrinkled membrane are strongly correlated with the wrinkling configurations. The rigidity is larger due to the heavier stress in the part of wrinkling wave peaks. Therefore, wave peaks are always located at the node lines of vibration mode. The vibration frequency obviously increases with the vibration of wave peaks.

Control of Surface Wrinkles on Shape Memory PLA/PPDO Micro‑nanofibers and Their Applications in Drug Release and Anti‑scarring

Micro-and nano-fibers of shape memory polymers(SMP)offer multiple advantages like high specific surface area,poros-ity,and intelligence,and are suitable for biomedical applications.In this study,biodegradable poly(p-dioxanone)(PPDO)materials were incorporated to improve the brittleness of shape memory polylactic acid(PLA),and plasticizers were used to reduce the transition temperature of SMP composites such that their transitions could be induced close to body temperature.Furthermore,an electrostatic spinning technology was applied to prepare SMP fibers with wrinkled structures and regulate their microstructures and morphologies such that the intelligent transition of wrinkled and smooth morphologies can be achieved on the fiber surface.The application of this controllable-morphology fiber membrane in intelligent controlled drug release and scar inhibition after Ahmed Glaucoma Valve(AGV)implantation was also studied.The drug release from the stretched and deformed drug-loaded fiber membranes was faster than those from membranes with the original shape.This membrane with micro-and nano-fibers had good anti-scarring effects that improved after drug loading.The achievement of intelligent controlled drug release and the evident anti-scarring effects of the membrane broaden the application of SMP fibers in the biomedical field.

Controllable formation of periodic wrinkles in Marangoni-driven self-assembled graphene film for sensitive strain detection

Controllable formation of microstructures in the assembled graphene film could tune the physical properties and broaden its applications in flexible electronics.Many efforts have been made to control the formation of wrinkles and ripples in graphene films.However,the formation of orderly wrinkles in graphene film remains a challenge.Here,we reported a simple strategy for the fabrication of graphene film with periodic and parallel wrinkles with a pre-stretched polydimethylsiloxane substrate.The width of the wrinkles in graphene can be controlled by changing the pre-stretched strain of the substrate.The average width of wrinkles in graphene film on the substrate with pre-stretched strain of 10%,20%,and 50%was about 3.68,2.99 and 2.01µm,respectively.The morphological evolution of wrinkled double-layered graphene under mechanical deformation was observed and studied.Furthermore,a strain sensor was constructed based on the wrinkled graphene,showing high sensitivity,large working range and excellent cyclic stability.These strain sensors show great potential in real-time motion detection,health surveillance and electronic skins.