Multiple forces facilitate the aquatic acrobatics of grasshopper and bioinspired robot.

Aquatic locomotion is challenging for land-dwelling creatures because of the high degree of fluidity with which the water yields to loads. We surprisingly found that the Chinese rice grasshopper Oxya chinensis, known for its terrestrial acrobatics, could swiftly launch itself off the water's surface in around 25 ms and seamlessly transition into flight. Biological observations showed that jumping grasshoppers use their front and middle legs to tilt up bodies first and then lift off by propelling the water toward the lower back with hind legs at angular speeds of up to 18°/ms, whereas the swimming grasshoppers swing their front and middle legs in nearly horizontal planes and move hind legs less violently (~8°/ms). Force measurement and model analysis indicated that the weight support could be achieved by hydrostatics which are proportionate to the mass of the grasshoppers, while the propulsions for motion are derived from the controlled limb-water interactions (i.e., the hydrodynamics). After learning the structural and behavioral strategies of the grasshoppers, a robot was created and was capable of swimming and jumping on the water surface like the insects, further demonstrating the effectiveness of decoupling the challenges of aquatic locomotion by the combined use of the static and dynamic hydro forces. This work not only uncovered the combined mechanisms responsible for facilitating aquatic acrobatics in this species but also laid a foundation for developing bioinspired robots that can locomote across multiple media.

Soap Film Transfer Printing for Ultrathin Electronics.

Flexible and stretchable electronics have attractive applications inaccessible to conventional rigid electronics. However, the mainstream transfer printing techniques have challenges for electronic films in terms of thickness and size and limitations for target substrates in terms of curvature, depth, and interfacial adhesion. Here a facile, damage-free, and contamination-free soap film transfer printing technique is reported that enables the wrinkle-free transfer of ultrathin electronic films, precise alignment in a transparent manner, and conformal and adhesion-independent printing onto various substrates, including those too topographically and adhesively challenging by existing methods. In principle, not only the pattern, resolution, and thickness of transferred films, but also the curvature, depth, and adhesion of target substrates are unlimited, while the size of transferred films can be as high as meter-scale. To demonstrate the capabilities of soap film transfer printing, pre-fabricated ultrathin electronics with multiple patterns, single micron resolution, sub-micron thickness, and centimeter size are conformably integrated onto the ultrathin web, ultra-soft cotton, DVD-R disk with the minimum radius of curvature of 131 nm, interior cavity of Klein bottle and dandelion with ultralow adhesion. The printed ultrathin sensors show superior conformabilities and robust adhesion, leading to engineering opportunities including electrocardiogram (ECG) signal acquisition and temperature measurement in aqueous environments.

Tree frogs (Polypedates dennysi) landing on horizontal perches: the effects of perch diameter.

Secure landing is indispensable for both leaping animals and robotics. Tree frogs, renowned for their adhesive capabilities, can effectively jump across intricate 3D terrain and land safely. Compared with jumping, the mechanisms underlying their landing technique, particularly in arboreal environments, have remained largely unknown. In this study, we focused on the landing patterns of the tree frog Polypedates dennysi on horizontally placed perches, explicitly emphasizing the influence of perch diameters. Tree frogs demonstrated diverse landing postures, including the utilization of: (1) single front foot, (2) double front feet, (3) anterior bellies, (4) middle bellies, (5) posterior bellies, (6) single hind foot, or (5) double hind feet. Generally, tree frogs favoured bellies on slimmer targets but double front feet on large perches. Analysis of limb-trunk relationships revealed their adaptability to modify postures, including body positions and limb orientations, for successful landing. The variations in the initial landing postures affected the subsequent landing procedures and, consequently, the dynamics. As the initial contact position switched from front foot back to the hind foot, the stabilization time decreased at first, reaching a minimum in middle belly landings, and then increased again. The maximum vertical forces showed an inverse trend, whereas the maximum fore-aft forces continuously increased as the initial contact position switched. As the perch diameter increased, the time expended dropped, whereas the maximum impact force increased. These findings not only add to our understanding of frog landings but also highlight the necessity of considering perch diameters and landing styles when studying the biomechanics of arboreal locomotion.

Magnetic-field induced shape memory hydrogels for deformable actuators.

Magnetic hydrogel actuators exhibit promising applications in the fields of soft robotics, bioactuators, and flexible sensors owing to their inherent advantages such as remote control capability, untethered deformation and motion control, as well as easily manipulable behavior. However, it is still a challenge for magnetic hydrogels to achieve adjustable stiffness and shape fixation under magnetic field actuation deformation. Herein, a simple and effective approach is proposed for the design of magnetic shape memory hydrogels to accomplish this objective. The magnetic shape memory hydrogels, consisting of methacrylamide, methacrylic acid, polyvinyl alcohol and Fe3O4 magnetic particles, which crosslinked by hydrogen bonds, are facilely prepared via one-pot polymerization. The dynamic nature of noncovalent bonds offers the magnetic hydrogels with excellent mechanical properties, precisely controlled stiffness, and effective shape fixation. The presence of Fe3O4 particles renders the hydrogels soft when subjected to an alternating current field, facilitating their deformation under the influence of an actuation magnetic field. After the elimination of the alternating current magnetic field, the hydrogels stiffen and attain a fixed actuated shape in the absence of any external magnetic field. Moreover, this remarkable magnetic shape memory hydrogel is effectively employed as an underwater soft gripper for lifting heavy objects. This work provides a novel strategy for fabricating magnetic hydrogels with non-contact reversible actuation deformation, tunable stiffness and shape locking.

Efficient fabrication of bioinspired soft, ridged-slippery surfaces with large-range anisotropic wettability for droplet manipulation.

The droplet lossless directional motion control on slippery surfaces holds immense promise for applications in microfluidic chips, hazardous substance detection, chemical dispensing, etc. However, a significant challenge in this domain lies in efficiently developing soft, slippery surfaces with large-range anisotropic wettability and compatibility for curved scenarios. This study addressed this challenge through a quick 3D printing-assisted method to produce soft, ridged-slippery surfaces (SRSSs) as the droplet manipulation platform. The SRSSs demonstrated substantial anisotropic rolling resistances, measuring 116.9 µN in the perpendicular direction and 7.7 µN in the parallel direction, exhibiting a ratio of 15.2. Combining several extents of anisotropic wettability on a soft substrate could realize diverse reagent manipulation functions. Furthermore, these SRSSs showcased high compatibility with various droplet constituents, impressive liquid impact resistance, self-repair capability, and mechanical durability and thermal durability, ensuring exceptional applicability. As proofs of concept, the SRSSs were successfully applied in droplet control and classification for heavy metal ion detection, mechanical arm-based droplet grab and release, and cross-species transport, showcasing their remarkable versatility, compatibility, and practicality in advanced droplet microfluidic chips and water harvesting applications.

A Systematic Review and Meta-Analysis of Efficacy and Safety of Cilostazol Prescription in Patients With Femoropopliteal Peripheral Artery Disease After Endovascular Therapy.

PURPOSE: The purpose of this study is to assess the efficacy and safety of cilostazol prescription in patients with femoropopliteal peripheral artery disease (PAD) after endovascular therapy (EVT). MATERIALS AND METHODS: We conducted a systematic review and meta-analysis of all studies reporting the outcomes of cilostazol after femoropopliteal EVT of PAD up to September 2022. Clinical outcomes of interest included primary patency, in-stent restenosis (ISR), vessel re-occlusion, freedom from target lesion revascularization (TLR), repeat revascularization, all-cause mortality, amputation, major adverse cardiovascular events (MACEs) and major adverse limb events (MALEs), and bleeding complication. RESULTS: A total of 4 randomized controlled trials (RCTs) and 8 observational studies containing a total of 4898 patients met the inclusion criteria and were included in this systematic review and meta-analysis. We found that the use of cilostazol was associated with higher primary patency after femoropopliteal artery EVT (odds ratio [OR]=1.67, 95% confidence interval [CI]=1.50-1.87, p<0.001, I2=33.2%), a lower risk of ISR (OR=0.43, 95% CI=0.29-0.63, p<0.001, I2=37.6%), repeat revascularization (OR=0.43, 95% CI=0.24-0.76, p<0.005, I2=27.4%), and vessel re-occlusion (OR=0.59, 95% CI=0.38-0.93, p<0.05, I2=0%). There was an increase in freedom from TLR rate (OR=2.19, 95% CI=1.58-3.05, p<0.001, I2=0%), as well as a reduction in the occurrence of MALEs (OR=0.50, 95% CI=0.29-0.85, p<0.05, I2=0%). However, there was no significant difference in amputation, MACEs, all-cause mortality, and major bleeding complications. Subgroup analysis showed that cilostazol treatment in patients with femoropopliteal drug-eluting stents (DES) implantation remained associated with higher primary patency and a lower risk of ISR. CONCLUSIONS: After EVT of femoropopliteal artery lesions, additional oral cilostazol enhances primary patency, reduces the occurrences of ISR and vessel re-occlusion, diminishes the risks associated with MALEs, lowers the need for repeat revascularization, and increases freedom from TLR rates. However, it does not impact amputation, MACEs, all-cause mortality, or major bleeding complications. These findings suggest cilostazol as a potentially safe and effective adjunct therapy in patients with femoropopliteal PAD after EVT. CLINICAL IMPACT: After undergoing endovascular therapy (EVT) for femoropopliteal artery lesions, the addition of cilostazol to antiplatelet therapy can significantly improve primary patency, reducing the incidence of in-stent restenosis, repeat revascularization, vessel re-occlusion, and major adverse limb events while increasing freedom from target lesion revascularization rate. The simultaneous use of drug-eluting stents in the femoropopliteal artery lesions, combined with cilostazol, potentially results in a synergistic anti-stenotic effect. This therapeutic approach does not appear to be associated with an increased risk of major bleeding events or all-cause mortality. These findings provide additional evidence supporting the treatment of anti-stenosis in patients with femoropopliteal artery lesions after EVT.

Efficacy and Safety of Covered Stents Versus Bare-Metal Stents for Aortoiliac Occlusive Disease: A Systematic Review and Meta-Analysis.

PURPOSE: This study aimed to assess the efficacy and safety outcome of covered stents (CSs), as compared with bare-metal stents (BMSs), for the treatment of patients with aortoiliac occlusive disease (AIOD). MATERIALS AND METHODS: A systematic literature search was conducted in PubMed, Embase, and Cochrane Library up to August 2023 to identify all studies comparing efficacy and safety outcomes of CSs versus BMSs for treating AIOD. Our outcome was primary patency, secondary patency, technical success, ankle-brachial index (ABI) variation, target lesion revascularization (TLR), limb salvage, complications, and long-term survival. Dichotomous outcomes were pooled as relative risks (RR) or hazard ratio with the 95% confidence interval (CI). Continuous outcomes were pooled as weighted mean differences and 95% CI. Model selection was based on the heterogeneity of the included studies. RESULTS: There were 10 studies (2 randomized controlled trials, 8 retrospective cohort studies), comprising 1676 sample size. Compared with BMSs, CSs use was associated with better primary patency of patients with a Trans-Atlantic Inter-Society Consensus II (TASC) D lesion (RR, 1.15, 95% CI, 1.04 to 1.27, p=0.007), TLR (RR, 0.39, 95% CI, 0.27 to 0.56, p<0.001), technical success (RR, 1.01, 95% CI, 1.00 to 1.02, p=0.010), and long-term survival (RR, 1.06, 95% CI, 1.01 to 1.11, p=0.020). There is no difference between CSs and BMSs regarding primary patency of all patients, secondary patency, variation in ABI, limb salvage, and complications. CONCLUSIONS: Compared with BMSs, CSs used in AIOD was associated with more favorable primary patency in patients with TASC D lesions, TLR, technical success rates, and patient long-term survival. These results provide evidence of the advantages of using CSs for AIOD treatment. Future studies focusing on long-term variations in ABI, primary patency of different degrees of calcification, vascular segments, and TASC classification are warranted. CLINICAL IMPACT: Although several studies evaluated the clinical efficacy of CS in the context of AIOD treatment, the significance and consistency of these findings were not determined to date. We found that CS was used in AIOD associated with better technical success rate, long-term patient survival, lower target lesion revascularization, and higher primary patency of patients with a Trans-Atlantic Inter-Society Consensus II D lesion when compared with BMSs. Our study provides evidence supporting the superiority of CSs over BMSs in the treatment of AIOD, and furnishing clinicians with guidance for treatment decisions.

Structural and chemical study of complex silver patterns additively manufactured by multi-photon reduction.

Multi-photon reduction (MPR) based on femtosecond laser makes rapid prototyping and molding in micro-nano scale feasible, but is limited in material selectivity due to lack of the understanding of the reaction mechanism in MPR process. In this paper, additively manufacturing of complex silver-based patterns through MPR is demonstrated. The effects of laser parameters, including laser pulse energies and scanning speeds, on the structural and chemical characteristics of the printed structures are systematically investigated. The results show that the geometric size of printed cubes deviates from the designed size further by increasing laser pulse energy or decreasing scanning speed. The reaction mechanism of MPR is revealed by studying the elemental composition and chemical structures of printed cubes. The evolution of Raman spectra upon the laser processing parameters suggests that the MPR process mainly includes two processes: reduction and decomposition. In the MPR process, silver ions are reduced and grow into particles by accepting the electrons from ethonal molecules; meanwhile carboxyl groups in polyvinylpyrrolidone are decomposed and form amorphous carbon that is attached on the surface of silver particles. The conductivity of silver wires fabricated by MPR reaches 2 × 105S m-1and stays relatively constant as varying their cross section area, suggesting excellent electrical conduction. The understanding of the MPR process would accelerate the development of MPR technology and the implementation of MPR in micro-electromechanical systems could therefore be envisioned.

Mosaic Patterned Surfaces toward Generating Hardly-Volatile Capsular Droplet Arrays for High-Precision Droplet-Based Storage and Detection.

Precise detection involving droplets based on functional surfaces is promising for the parallelization and miniaturization of platforms and is significant in epidemic investigation, analyte recognition, environmental simulation, combinatorial chemistry, etc. However, a challenging and considerable task is obtaining mutually independent droplet arrays without cross-contamination and simultaneously avoiding droplet evaporation-caused quick reagent loss, inaccuracy, and failure. Herein, a strategy to generate mutually independent and hardly-volatile capsular droplet arrays using innovative mosaic patterned surfaces is developed. The evaporation suppression of the capsular droplet arrays is 1712 times higher than the naked droplet. The high evaporation suppression of the capsular droplet arrays on the surfaces is attributed to synergistic blocking of the upper oil and bottom mosaic gasproof layer. The scale-up of the capsular droplet arrays, the flexibility in shape, size, component (including aqueous, colloidal, acid, and alkali solutions), liquid volume, and the high-precision hazardous substance testing proves the concept's high compatibility and practicability. The mutually independent capsular droplet arrays with amazingly high evaporation suppression are essential for the new generation of high-performance open-surface microfluidic chips used in COVID-19 diagnosis and investigation, primary screening, in vitro enzyme reactions, environmental monitoring, nanomaterial synthesis, etc.

Comparison of Operative Time Between Robotic and Laparoscopic Low Anterior Resection for Rectal Cancer:A Systematic Review and Meta-Analysis.

Background. Previous studies have shown that the robotic approach has better perioperative outcomes but longer operative time than the laparoscopic approach for patients undergoing low anterior resection. However, the impact of the learning curve on operative time is controversial. This study aimed to evaluate operative time and associated outcomes by comparing robotic low anterior resection (R-LAR) with laparoscopic low anterior resection (L-LAR). Methods. Pubmed, Embase, Cochrane Library, Ovid, Web of Science, and CNKI databases were interrogated from the inception to April 2021. Two authors screened all records through full-text reading and extracted and synthesized the data using a structured table. A random-effect model was used to evaluate heterogeneity. Meta-analysis was implemented by R 4.1.1 meta-package. Results. Twelve studies (1684 patients) were included in the present review. R-LAR compare to L-LAR approach has significant differences in operative time (min) (MD = 23.14, 95% CI: 6.89-39.40, P < .01), blood loss (mL) (MD = -42.66, 95% CI: [-68.51, -16.81], P < .01), number of lymph nodes harvested (MD = 1.06, 95% CI: [.16; 1.97], P < .05). Sensitivity analysis of the number of lymph nodes harvested indicated that the overall effect might not be stable. Subgroup analysis showed that mean age and sample size of R-LAR were 2 important factors affecting the estimation. Conclusions. Our results presented a prolonged operative time with the robotic approach compared to laparoscopy, but this gap diminished as the sample size increased. It might be more timesaving once surgeons are familiar with surgical robots.

Identification of upper GI diseases during screening gastroscopy using a deep convolutional neural network algorithm.

BACKGROUND AND AIMS: The clinical application of GI endoscopy for the diagnosis of multiple diseases using artificial intelligence (AI) has been limited by its high false-positive rates. There is an unmet need to develop a GI endoscopy AI-assisted diagnosis system (GEADS) to improve diagnostic accuracy and clinical utility. METHODS: In this retrospective, multicenter study, a convolutional neural network was trained to assess upper GI diseases based on 26,228 endoscopic images from Dazhou Central Hospital that were randomly assigned (3:1:1) to a training dataset, validation dataset, and test dataset, respectively. To validate the model, 6 external independent datasets comprising 51,372 images of upper GI diseases were collected. In addition, 1 prospective dataset comprising 27,975 images was collected. The performance of GEADS was compared with endoscopists with 2 professional degrees of expertise: expert and novice. Eight endoscopists were in the expert group with >5 years of experience, whereas 3 endoscopists were in the novice group with 1 to 5 years of experience. RESULTS: The GEADS model achieved an accuracy of .918 (95% confidence interval [CI], .914-.922), with an F1 score of .884 (95% CI, .879-.889), recall of .873 (95% CI, .868-.878), and precision of .890 (95% CI, .885-.895) in the internal validation dataset. In the external validation datasets and 1 prospective validation dataset, the diagnostic accuracy of the GEADS ranged from .841 (95% CI, .834-.848) to .949 (95% CI, .935-.963). With the help of the GEADS, the diagnosing accuracies of novice and expert endoscopists were significantly improved (P < .001). CONCLUSIONS: The AI system can assist endoscopists in improving the accuracy of diagnosing upper GI diseases.

Drying temperature regulates vigor of high moisture rice seeds via involvement in phytohormone, ROS, and relevant gene expression.

BACKGROUND: Rice is an important food crop in China. Seed drying is an important step in the production of rice seeds. However, the regulatory mechanism of the effect of drying temperature on vigor of rice seeds with high initial moisture content (IMC) has not been examined. RESULTS: This study presents hot-air drying of rice seeds with high IMC (>30%) to assess the effect of drying temperature (35, 41, and 47 °C) on drying performance and seed vigor in terms of germination capacity. The results show a significant positive correlation between the drying rate, seed temperature, and drying temperature. High-temperature drying tends to cause a large accumulation of reactive oxygen species (ROS) and increases the activity of antioxidant enzymes in rice seeds. High-temperature drying also significantly increased abscisic acid (ABA) content and decreased gibberellin (GA) content through the regulation of the activity of metabolism related-enzymes. Moreover, changes in GA and ABA metabolism during early seed germination might be an important reason for the decrease in seed vigor with high-temperature drying. High-temperature drying also significantly inhibited the activity of α-amylase during early seed germination. CONCLUSION: A drying temperature of 35 °C was safe for rice seeds with high IMC, whereas higher drying temperatures (41 and 47 °C) reduced rice seed vigor remarkably. The metabolism of ROS, antioxidant enzymes, GA, ABA, and α-amylase might be closely involved in the regulation of the effect of drying temperature on the seed vigor of rice seeds with high IMC. The results of this study, therefore, provide a theoretical basis and technical guidance for mechanical drying of rice seeds. © 2020 Society of Chemical Industry.

Combined fenestrated/chimney thoracic endovascular repair for the treatment of blunt traumatic aortic injury: A case report.

Blunt traumatic thoracic aortic injury (BTAI) is an extremely serious medical condition with a high rate of associated mortality. Recent advances in techniques such as thoracic endovascular repair offer new opportunities to manage the critical BTAI patients in an efficacious yet less invasive manner. A 65 year-old-male suffered from multiple injuries after a fall, including BTAI in the aortic arch, which resulted in dissection of the descending thoracic-abdominal aorta and iliac artery, development of an intimal flap in the left common carotid artery, and dissection of the left subclavian artery. Based on the imaging information of this patient and our clinical experience, the combined treatment of fenestrated thoracic endovascular repair and a chimney technique was immediately planned to fully repair these dissections and moreover prevent further dissection of the branching vessels, additionally to ensure sufficient blood flow in the left subclavian artery and left common carotid artery. The intervention yielded satisfactory early outcomes. Follow-up assessment at six months reported no symptoms or complications associated with the stent-graft. Computed tomography angiography further confirmed adequate stent-graft coverage of the aortic injury.

Large electrostrain induced by reversible domain switching in ordered ferroelectric nanostructures with optimized geometric configurations.

Large electromechanical response of ferroelectric materials is particularly appealing for applications in functional devices, such as sensors and actuators. For conventional ferroelectric materials, however, the mechanical strain under an external electric field, i.e. the electrostrain, is often limited by the intrinsic electromechanical property of the materials. Domain engineering has been suggested as a practical way to overcome this limitation and to enhance the electrostrain. Here, we show from phase-field simulations that reversible domain switching in ordered ferroelectric nanostructures with optimized geometric configurations can enhance the electrostrain significantly. In the presence of an external electric field, the domains in such nanostructures can switch from a multi-domain state confined by the geometric configurations to a mono-domain state. It is interesting that the domains can switch back to the multi-domain state due to strong internal depolarization fields once the electric field is removed. As a result, accompanying the reversible domain switching behavior, a large and reversible electrostrain can be obtained. Going further, it is found that the temperature dependence of the large electrostrain is similar to that of polarization in such nanostructures. The present work opens a perspective to obtaining large electrostrain in nanoscale ferroelectrics, which holds great promise for designing electromechanical functional devices with high performance.

[Clinical features of coronavirus disease 2019 in children aged <18 years in Jiangxi, China: an analysis of 23 cases].

OBJECTIVE: To study the clinical features of coronavirus disease 2019 (COVID-19) in children aged <18 years. METHODS: A retrospective analysis was performed from the medical data of 23 children, aged from 3 months to 17 years and 8 months, who were diagnosed with COVID-19 in Jiangxi, China from January 21 to February 29, 2020. RESULTS: Of the 23 children with COVID-19, 17 had family aggregation. Three children (13%) had asymptomatic infection, 6 (26%) had mild type, and 14 (61%) had common type. Among these 23 children, 16 (70%) had fever, 11 (48%) had cough, 8 (35%) had fever and cough, and 8 (35%) had wet rales in the lungs. The period from disease onset or the first nucleic acid-positive detection of SARS-CoV-2 to the virus nucleic acid negative conversion was 6-24 days (median 12 days). Of the 23 children, 3 had a reduction in total leukocyte count, 2 had a reduction in lymphocytes, 2 had an increase in C-reactive protein, and 2 had an increase in D-dimer. Abnormal pulmonary CT findings were observed in 12 children, among whom 9 had patchy ground-glass opacities in both lungs. All 23 children received antiviral therapy and were recovered. CONCLUSIONS: COVID-19 in children aged <18 years often occurs with family aggregation, with no specific clinical manifestation and laboratory examination results. Most of these children have mild symptoms and a good prognosis. Epidemiological history is of particular importance in the diagnosis of COVID-19 in children aged <18 years.

Theoretical and Experimental Studies on the Controllable Pancake Bouncing Behavior of Droplets.

A droplet that impacts on a superhydrophobic surface will undergo a process of unfolding, contracting, and finally rebounding from the surface. With regards to the pancake bouncing behavior of a droplet, since the retraction process of the droplet is omitted, the contact time is greatly shortened compared to the normal type of bouncing. However, the quantitative prediction to the range of droplet pancake bouncing and the adjustment of pancake bouncing state have yet to be probed into. In this paper, we reported the controllable pancake bouncing of droplets by adjusting the size of the superhydrophobic surface with microstructures. In addition, we also discovered a dimensional effect with regards to pancake bouncing, namely, the pancake bouncing would be more likely to happen on the surfaces with large post spacing for the droplet with the larger radius. The contact time could be reduced to 2 ms by adjusting the size of the microstructures and the radius of the droplets. Based on the relationship between the droplet bouncing state and the surface microstructure size, we are able to propose reasonable dimensions for the surfaces in order to control pancake bouncing.

Theoretical and Experimental Study of Reversible and Stable Wetting States of a Hierarchically Wrinkled Surface Tuned by Mechanical Strain.

The wetting behavior of hierarchically wrinkled surfaces has attracted great interest because of its broad application in flexible electronic, microfluidic chip, and biomedicine. However, theoretical studies concerning the relationship between the apparent contact angle and mechanical strain applied on the soft and flexible surface with a hierarchically wrinkled structure are still limited. We established a theoretical framework to describe and understand how prestrain and applied dynamic strain reversibly tune the wettability of the hierarchically wrinkled surface. More specifically, a direct relationship between the mechanical strain and contact angle was built through reversible tuning of the amplitude and the wavelength of the wrinkled structures caused by mechanical strain, which allowed for more precise adjustment of surface wettability. To verify the accuracy of the theoretical relationship between the contact angle and mechanical strain, a soft surface with a hierarchically wrinkled structure was prepared by combining wrinkled microstructures and strip ones. The results showed that the experimental contact angles were in agreement with the theoretical ones within a limited error range. This will be helpful for further investigation on the wettability of hierarchically wrinkled surfaces.

Wetting and Dewetting Transitions on Submerged Superhydrophobic Surfaces with Hierarchical Structures.

The wetting transition on submersed superhydrophobic surfaces with hierarchical structures and the influence of trapped air on superhydrophobic stability are predicted based on the thermodynamics and mechanical analyses. The dewetting transition on the hierarchically structured surfaces is investigated, and two necessary thermodynamic conditions and a mechanical balance condition for dewetting transition are proposed. The corresponding thermodynamic phase diagram of reversible transition and the critical reversed pressure well explain the experimental results reported previously. Our theory provides a useful guideline for precise controlling of breaking down and recovering of superhydrophobicity by designing superhydrophobic surfaces with hierarchical structures under water.

Smart design of wettability-patterned gradients on substrate-independent coated surfaces to control unidirectional spreading of droplets.

Highly adherent wettability patterns on the substrate-independent superhydrophobic surfaces of trimethoxyoctadecylsilane modified titanium dioxide (TiO2)-based coatings were prepared by using commercial photolithography. Three custom unidirectional channels with gradient wettability patterns were obtained by spatially selective wettability conversion from superhydrophobic to superhydrophilic when the coatings were exposed to ultraviolet light (∼365 nm). The movement behavior of droplets on these unidirectional channels was studied and the displacement of droplet movement was effectively controlled. Integrating the idea of gradient wettability patterns into planar microfluidic devices (microreactors), a self-driven fluid transport was achieved to realize droplet metering, merging or reaction, and rapid transport. This self-driven fluid transport with gradient wettability patterns has great potential in fabricating a new category of pump-free microfluidic systems that can be used in various conditions.

Hollow Au-Cu2O Core-Shell Nanoparticles with Geometry-Dependent Optical Properties as Efficient Plasmonic Photocatalysts under Visible Light.

Hollow Au-Cu2O core-shell nanoparticles were synthesized by using hollow gold nanoparticles (HGNs) as the plasmon-tailorable cores to direct epitaxial growth of Cu2O nanoshells. The effective geometry control of hollow Au-Cu2O core-shell nanoparticles was achieved through adjusting the HGN core sizes, Cu2O shell thicknesses, and morphologies related to structure-directing agents. The morphology-dependent plasmonic band red-shifts across the visible and near-infrared spectral regions were observed from experimental extinction spectra and theoretical simulation based on the finite-difference time-domain method. Moreover, the hollow Au-Cu2O core-shell nanoparticles with synergistic optical properties exhibited higher photocatalytic performance in the photodegradation of methyl orange when compared to pristine Cu2O and solid Au-Cu2O core-shell nanoparticles under visible-light irradiation due to the efficient photoinduced charge separation, which could mainly be attributed to the Schottky barrier and plasmon-induced resonant energy transfer. Such optical tunability achieved through the hollow cores and structure-directed shells is of benefit to the performance optimization of metal-semiconductor nanoparticles for photonic, electronic, and photocatalytic applications.