Aquatic Devices Research Articles

A Renew Microbial Degradation and Valorisation of Plastic Wastes Management in the Environment

Abstract: A developing accumulation of plastic wastes has turn out to be a severe environmental and social issue. It’s far urgent to expand innovative processes for the disposal of plastic wastes. In recent years, reports on biodegradation of synthetic plastics by using microorganisms or enzymes have sprung up, and those offer a opportunity to broaden biological treatment generation for plastic wastes. on this assessment, we've comprehensively summarized the microorganisms and enzymes which are able to degrade an expansion of normally used artificial plastics, which includes polyethylene (PE), polystyrene (PS), polypropylene (PP), polyvinyl chloride (%), polyurethane (PUR), and polyethylene terephthalate (pet). further, we have highlighted the microbial metabolic pathways for plastic depolymerization merchandise and the modern-day attempts in the direction of usage of such products as feedstock’s for microbial manufacturing of chemical substances with excessive fee. Taken together, these findings will contribute to building a theory of bio-up biking plastic wastes through connecting the biodegradation of plastic wastes to the biosynthesis of treasured chemical compounds in microorganisms. Closure, but not least, we've discussed the demanding situations in the direction of microbial degradation and valorization of plastic wastes. Plastics are found everywhere in the area and grow into a hot topic in educational circles. Big studies have focused on analytical techniques, source, abundance, transport, fate, degradation of plastics inside the environment and threats to herbal surroundings, wildlife or even human fitness. However, characteristics of plastic pollution, which might be important to recognize this rising problem, continue to be unknown to this point. Here, this paper opinion the essential characteristics of plastic pollutants within the environment to beautify present knowledge of this problem. Those traits, inclusive of diversity, persistence, global problems, mixed pollution and threats to organisms and human fitness, are severely summarized in this work. In addition, “plastic cycle” inside the environment, particularly, aquatic, atmospheric, and terrestrial device is also mentioned in this assessment. Sooner or later, we highlight current demanding situations of plastic pollution posed to the public and also suggest the studies developments in destiny paintings.

Propaedeutic Study of Biocomposites Obtained With Natural Fibers for Oceanographic Observing Platforms

In response to the pervasive anthropogenic pollution of the ocean, this manuscript suggests the use of biodegradable elastomers in marine applications. The present study characterizes 25 samples of highly biodegradable polymers, obtained blending a base elastomer with natural fibers. Mechanical analysis and Scanning Electron Microscope imaging, reveal how base polymers behave differently depending on the plant fiber chosen, on the external forcing—exposure to water—and on the doses that constitute the final biocomposite. Results suggest that EcoflexTM 00-30 and EcoflexTM 00-50, mixed with potato starch, perform best mechanically, maintaining up to 70% of their maximum tensile strain. Moreover, early signs of degradation are visible on polysiloxane rubber blended with 50% vegetable fibers after 19 hours in distilled water. Analyses demonstrate that highly biodegradable elastomers are good candidates to satisfy the requirements of aquatic devices. Furthermore, the discussed materials can improve the dexterity and biodegradability of marine technology.

Learning swimming escape patterns for larval fish under energy constraints

Swimming organisms can escape their predators by creating and harnessing unsteady flow fields through their body motions. Stochastic optimization and flow simulations have identified escape patterns that are consistent with those observed in natural larval swimmers. However, these patterns have been limited by the specification of a particular cost function and depend on a prescribed functional form of the body motion. Here, we deploy reinforcement learning to discover swimmer escape patterns for larval fish under energy constraints. The identified patterns include the C-start mechanism, in addition to more energetically efficient escapes. We find that maximizing distance with limited energy requires swimming via short bursts of accelerating motion interlinked with phases of gliding. The present, data efficient, reinforcement learning algorithm results in an array of patterns that reveal practical flow optimization principles for efficient swimming and the methodology can be transferred to the control of aquatic robotic devices operating under energy constraints.

Research Report: Efficacy and Safety of a Novel Aquatic Device for Children With Postural Dysfunction

Background and Purpose: Children with postural dysfunction often enjoy aquatic activities but are limited in their ability to play and interact in the water due to limited motor control and safety concerns. The purpose of this study was to explore the benefits of postural contexts provided by a novel aquatic device (Water Strider) in children with postural dysfunction. Providing stable vertical support is hypothesized to improve overall environmental interactions/social engagement and increase safety, autonomy, and motivation for movement (kicking and reaching). Methods: The proposed device provided external support that could be modified on the basis of user-specific level of head and trunk control. Feasibility, safety, and efficacy of the device were tested for 9 children (aged 2-8 years) with postural dysfunction (7 with cerebral palsy). For this purpose, a 10-minute aquatic trial for baseline aquatic activities along with use of the Water Strider was performed for comparison with video behavior coding to quantify arm and leg movements, assistance, and hazardous events (water in eyes or water in mouth). Results: Total assistance required significantly decreased from baseline (100%) to the Water Strider (21%; F 1,8 = 384.4, P ≤ .001), and significantly fewer instances where children were found to have water in their mouth occurred across all participants (baseline: 12 events; Water Strider: 0 events). Significant increase in total leg movement/reciprocal kicking (F 1,8 = 8.84, P < .001; F 1,8 = 11.1, P = .003) and decrease in arm movements (F 1,8 = 0.036, P < .001) with relation to the level of trunk control were also observed.

Green Method for Fabrication of an Underwater Superoleophobic Phosphor-Copper Mesh and Transportation of Oily Liquids.

Sea cucumber-shaped Cu2O nanostructures are constructed on a phosphor-copper mesh by employing a one-step immersion process accomplished in distilled water without introducing any additional reagent. The phosphor-copper mesh with a Cu2O structure thereon exhibits significant hydrophilicity and induces a large superoleophobic force at the oil/water interface. The method used for preparing the Cu2O nanostructures represents an inexpensive, fast, and environmentally friendly approach, along with satisfying the requirements of large-scale preparation. It is found that the pickling degree of the phosphor-copper mesh during surface cleaning plays a major role in the oxidation process of the surface for the growth of Cu2O nanostructures. Nanostructures with different morphologies can be achieved by accurately controlling the surface pickling degree. Interestingly, an underwater superoleophobic "pipe" developed using the as-prepared phosphor-copper mesh can realize gravity (buoyancy)-driven oily liquid transport in an aqueous environment, with no associated contamination by the oil. This study provides a simple method to realize surface-functionalization and demonstrates a new route for achieving liquid transportation without external energy and would help to design smart aquatic devices for diverse liquid transport thereby, enabling oil handling and oil spill cleanup.

Environment-responsive coatings with recoverable in-air superamphiphobicity and underwater superoleophobicity

Creating a surface that is simultaneously amphiphobic in air and oleophobic in water is energy unfavorable. To overcome this counterintuitive scientific problem, we demonstrate a general approach for construction of environment-responsive coatings made of perfluorinated surfactant substituted polyelectrolyte multilayers (PEMs). Sum frequency generation (SFG) vibrational spectroscope indicates that in an air environment, the film coatings orderly protrude their hydrophobic perfluorinated tails into air to decrease surface energy, giving rise to amphiphobicity with water and hexadecane contact angles (CAs) of ~114° and ~65° respectively on flat substrates. When the coated substrates are placed in water, the coatings will undergo a reconfiguration, the perfluorinated chains of the coatings instantaneously migrate and embed themselves into the film bulk to optimize their surface energy, leaving hydrophilic portions and positively charged groups exposed at the film-water interface (confirmed by surface zeta potential, XPS and SFG), which leads to an underwater oleophobicity with hexadecane CA of ~147°. By applying the coatings on roughed substrates, e.g., fabrics, both superamphiphobicity and underwater superoleophobicity were achieved with in-air water and hexadecane CAs of ~155° and ~152°, and underwater hexadecane CA of ~169°, respectively. Moreover, the coatings with these special wettabilities exhibit a good self-healing performance upon both plasma-induced surface decomposition and salt treatment. These coatings may bring in new insights of surface wettability and offer great potential in self-cleaning, anti-oil-fouling both in air and water (especially for aquatic devices working in oil spill situations).

Highly Floatable Superhydrophobic Metallic Assembly for Aquatic Applications.

Water-repellent superhydrophobic (SH) surfaces promise a wide range of applications, from increased buoyancy to drag reduction, but their practical use is limited. This comes from the fact that an SH surface will start to lose its efficiency once it is forced into water or damaged by mechanical abrasion. Here, we circumvent these two most challenging obstacles and demonstrate a highly floatable multifaced SH metallic assembly inspired by the diving bell spiders and fire ant assemblies. We study and optimize, both theoretically and experimentally, the floating properties of the design. The assembly shows an unprecedented floating ability; it can float back to the surface even after being forced to submerge under water for months. More strikingly, the assembly maintains its floating ability even after severe damage and piercing in stark contrast to conventional watercrafts and aquatic devices. The potential use of the SH floating metallic assembly ranges from floating devices and electronic equipment protection to highly floatable ships and vessels.

Integrated CNTs/SiO2 nano-additives on SBS polymeric superhydrophobic coatings for self-cleaning

ABSTRACTStyrene–butadiene-styrene triblock copolymers were blended with carbon nanotubes (CNTs)/SiO2 nano-additives to fabricate superhydrophobic coatings for self-cleaning. When the loading of nano-additives is 20 wt-% and the mass ratio of CNTs to SiO2 is 4:1, the nanocomposite coatings show the best self-cleaning property with water contact angle of 152.5° and contact angle hysteresis of 3.2°. In addition, the superhydrophobic coatings exhibited good thermal stability and high mechanical stability. The superhydrophobic coatings might be extended to the design of novel superfloating and drag-reducing aquatic devices. Owing to its flexibility and simplicity, the method is not only a facile and inexpensive way to achieve the lotus effect but could also create coatings with high values in practical application.

Buoyant and durable oil/water separation mesh for continuous and efficient collection of both oil slick and underwater oil leakage

Oil/water separation has aroused widespread concern owning to the severeenvironmental pollution and energy waste result from the frequent oil spill accidents and a great deal of discharged oily sewage. Thus, an efficient oil/water separation method is highly demanded but remains a challenge. To this respect, a specific mesh with super water repellency, good durability, excellent corrosion resistance and buoyant property has been developed in this work via a facile strategy. By virtue of the above superior properties, the resultant superhydrophobic mesh exhibits ultrahigh permeation flux (>22000 L·m−2·h−1) and high separation efficiency (>98.5%) for gravity-induced oil-water separation. Moreover, the resultant mesh can be designed as an oil-collecting device to continuously separate both oil slick and underwater oil leakage from bulk water under the driving of negative pressure, showing a prominent collection capability. It’s worth noting that the effective continuous collection of flowing oils underwater has been rarely reported in the emerging works. Moreover, the obtained mesh also possesses excellent load carrying capacity by buoyancy testing. With the advantages of the attractive property, the as-prepared superwetting mesh will hold great potential in developing of aquatic devices that can move freely on water with great water repellency, which is helpful for large-scale oil spill cleanup.

Multifunctional Superwettable Material with Smart pH Responsiveness for Efficient and Controllable Oil/Water Separation and Emulsified Wastewater Purification.

Developing multifunctional superwettable materials is highly demanded in the oil/water separation field but remains challenging due to the critical limitations of complex fabrication strategy and high cost. Herein, based on the cost-effective kaolin nanoparticles, we present a convenient and mild strategy for fabricating a smart superwettable material with multiple excellent performances, such as pH-responsive water wettability, self-cleaning property, favorable buoyancy, and air purification performance. By virtue of the dual rough surface structure and special chemical composition, the resultant material surface exhibits a superior pH-dependent wettability, which can be reversibly switched between superamphiphobicity and superhydrophilicity-superoleophobicity for many times in accordance with the pH value of the corresponding aqueous solution. As a result, the obtained superwettable material with reversible and controllable water wettability can be applied in efficient and continuous separation of multiple types of oil/water mixtures, especially the highly emulsified oil/water emulsions, via in situ or ex situ wettability change. To our knowledge, the smart material with the wetting property of superamphiphobicity that can be used for continuous emulsified wastewater purification has been rarely discussed in the emerging research works. In addition, the as-prepared material presents universal applicability to diversiform substrates and exhibits robust durability and stability against high-concentration salt solutions and rigorous mechanical abrasion. All of these above-mentioned advantages indicate that the as-prepared superwettable material will hold great potential in various practical applications, including oily wastewater remediation, smart aquatic device fabrication, liquid droplet manipulation, guiding liquid movement, and optimizing multiple operations in industrial fields.

Removal of Oil Spills through a Self-Propelled Smart Device.

Oil/water separation through superhydrophobic/superoleophilic materials has attracted considerable interest over the past decades; however, dealing with oil spills on broad waters through an active way remains a challenge. Herein, we report a self-propelled smart device driven by the decomposition of hydrogen peroxide that can spontaneously move on the water surface and collect floating oil droplets inside with superhydrophobic and superoleophilic properties. Moreover, the self-propelled smart device exhibits excellent stability and high efficiency for oil/water separation. We believe this study may provide a promising strategy for fabricating smart aquatic devices that have potential applications in water remediation.

Controlled Movement of a Smart Miniature Submarine at Various Interfaces.

Smart miniaturized aquatic devices have many important applications, but their locomotion at different interfaces remains a challenge. Here, we report a smart miniaturized submarine moving at various air/liquid or oil/water interfaces. The microsubmarine is fabricated by a CO2-responsive superhydrophobic copper mesh and is driven by the Marangoni effect. The microsubmarine can not only transfer among different interfaces reversibly but also move horizontally at the interfaces freely. The unique locomotion of the device is attributed to a CO2-triggered switch between superhydrophobicity and underwater superoleophobicity. Moreover, the microsubmarine exhibits good stability and excellent oil repellence at the oil/water interface. Our study provides a strategy for fabricating smart aquatic devices that have potential applications in environment monitoring, water purification, channel-free microfluidics, and so on.

Serially Connectable Sediment Microbial Fuel Cells using Dipole Graphite Solids and Voltage Reversal Suppression

AbstractSediment microbial fuel cells (SMFCs) are installed in natural water systems for the on‐site power source of aquatic devices; however, the power generated from single unit is not enough to operate certain devices. To overcome this drawback, the series connection of SMFCs is indispensable. We describe a dipole‐electrode‐containing stacked SMFC system operated in series connection mode. Two SMFC units were fabricated, which produced maximum current densities of 492 and 302 mA m−2, respectively. They were connected in series and operated at 1.45 V, which is close to the sum of the individual voltages. Even though voltage reversal inevitably occurred in the connected mode, it was suppressed by adjusting the internal resistance of each SMFC to be very close within a few Ω. We achieved a maximum power density at a high voltage over 123 mW m−2 at 0.6 V and enhanced the available maximum current density (i.e., no voltage reversal) by 269 to 320 mA m−2. We have developed a serially connectable SMFC system with an improved maximum power at a higher voltage than that of a single SMFC and we suggest a method for voltage reversal control for the further test of multistacked SMFCs.

Enzymes Confinement in Gold Nanospikes Electrodes Fabricated By Metal-Assisted Chemical Etching for Enhanced Electron Transfer

The field of enzyme based biofuel cells (EBFC) which utilize enzymes that can consume complex fuels (i.e. sucrose, fructose, etc.) and fuel mixtures to produce electrical energy has expanded over the last 3 decades, and it is now possible to consider applications for implantable fuel cells, bio-battery and aquatic device power source. The last three decades have seen major advancements in the field to enhance the open circuit potentials, current and power densities, fuel efficiency and biocatalyst stability. These advances have resulted in open circuit potentials increasing from 175 mV to almost 1 V and current densities increasing from μA/cm2 to mA/cm2. These increases come from enhanced electrochemically assessable surface areas with nanomaterials, increasing the oxidation reaction activity of anodes with enzyme cascades, metabolons, and optimal cell design to minimize internal resistance. However, further researches into improving power density over 1~5 mW are still needed to supply the power for stable operation of target devices. In this situation, the stable power output is hampered by a low level of electron transfer rate since electron transfer is known as crucial factor that determines performance of EBFC systems. The low level of electron transfer rate is resulted from several reasons that are related to protein structure and enzyme-layer formation. In detail, the redox center where electron is generated is often buried inside the protein matrix and moreover, enzymes are randomly oriented or forms multi-layers of enzymes during loaded on electrode, all of which attribute to long distance of electron transfer and degrade the performance of enzymatic electrode as well. To alleviate these problems, many groups have studied to develop the methods to enhance the electron transfer in these circumstances. Especially, construction of nanostructured high surface electrodes has been spotlighted because it could facilitate the electron transfer and thus performance of enzymatic electrode. In this research, we attempted to fabricate the nanostructured bioanode, optimizing the electron transfer from enzymes to electrode by control of enzyme layer thickness on the electrode surface. Genetically expressed FAD-dependent glucose dehydrogenase is immobilized on Au electrode modified by metal assisted chemical etching (MaCE). Recently, the fabrication of silicon (Si) subwavelength structure (SWS) by means of metal-assisted chemical etching (MaCE) has received increasing attention for its several merits during the modification of electrode surface that low-cost, fast, and scalable. Through this methodology, we fabricated nanospikes in pyramidal structure on the electrode surface, in which the nanospikes exist periodically with a sub-wavelength pitch all over the electrode surface. The effect of nanofabrication in this study is that immobilized enzyme on electrode surface are facilitated to be evenly distributed on the electrode surface. The periodically inclined structure grants equal opportunity of enzyme loading for unit area of electrode surface. By achieving the uniform distribution of enzymes, the distance between enzyme redox center and electrode surface can be reduced by excluding enzyme multilayers. Here, we experimentally studied the effect of pyramidal structure on enzymatic behaviors. During the experiment, the silicon (Si) wafer was selected with high conductive type for eliminating the possible overpotential that could be occured from the support material. Ag nanoparticles were used to assist the etching process of Si substrate, providing catalytic sites. The fabrication utilizing various diameter of Ag nanoparticles and etching times were conducted for having electrode candidates with different periodicities and pitch sizes. The optimized structure was confirmed by testing with electrochemical method, cyclic voltammetry (CV), and the optical slope which includes periodicity and pitch size was determined. Based on this research, it was concluded that electrode morphology is parameter that determines the performance of EBFC. Therefore, electrode structure for EBFC should be constructed in consideration of bio-electrode compatibility, not just of high surface area. Figure 1

Three-dimensional topographies of water surface dimples formed by superhydrophobic water strider legs

A water strider has a remarkable capability to stand and walk freely on water. Supporting forces of a water strider and a bionic robot have been calculated from the side view of pressed depth of legs to reconstruct the water surface dimples. However, in situ measurements of the multiple leg forces and significantly small leg/water contact dimples have not been realized yet. In this study, a shadow method was proposed to reconstruct the in situ three-dimensional topographies of leg/water contact dimples and their corresponding supporting forces. Results indicated that the supporting forces were affected by the depth, width, and length of the dimple, and that the maximum dimple depth was not proportional to the supporting forces. The shadow method also has advantages in disclosing tiny supporting force of legs in their subtle actions. These results are helpful for understanding the locomotion principles of water-walking insects and the design of biomimetic aquatic devices.

Effects of 8 Weeks Water Cure with Aquatic Devices on Static Balance and Velocity of Gait among Elderly Men

Background: Aging is a stage of life that increases the risk of physical diseases, some of which are chronic and can affect different dimensions of life’s quality. Hydrotherapy is used to treat rheumatic, orthopedic and neurological disorders. It has been the subject of investigations regarding balance and gating recovery in elderly people. Objective: To evaluate the effect 8 weeks water cure program with aquatic devices on static balance and velocity of gait in elderly men.Methods: : Fifteen old men were chosen purposely by age mean and Std 58±6.5, length 167.12±7.35 cm, weight 75.64±7.64. . We used the Sharpened Romberg test (static balance with eyes open and close) and Timed Up & Go (for evaluating velocity of gait). we used a selected program in water with aquatic devices in 8 weeks. Water exercise session included of three parts warm up, main part of exercise, and cool down. we analyzed the achieved data by a correlated t-test at a meaningful level (p≤0.05).Results: Among the post-test and pre-test Romberg test ( p≤013) and the velocity of gait (p≤005) were recovered meaningfully after the program.Conclusions: The results showed that participating in an exercise in water program with aquatic devices on a regular basis can be considered as an effective and reliable method to increase balance, and it can promote quality and velocity of gait among these aged men.

Water repellent Ag/Ag2O@bamboo cellulose fiber membrane as bioinspired cargo carriers

Water striders can walk on water. To mimic this function, a porous membrane consisted of bamboo cellulose fiber was hybridized with Ag/Ag2O nanoparticles through a facile in situ method to produce water repellent and well-ventilated materials. Herein, we report the sole surface roughness created by Ag/Ag2O nanoparticles could render the membrane a water contact angle (CA) of 140±3.0°. When floating on water, the hybrid membrane was able to support a heavy load more than 10 times the weight of the membrane itself. Additionally, this membrane demonstrated capabilities for oil sampling under water or oil/water separation and strong antibacterial activity against Escherichia coli. Thus we foresee that this novel hybrid membrane can be potentially utilized as drag-reducing, gas permeable and antibiotic substrates for constructing miniature aquatic devices.

A Smart “Strider” Can Float on Both Water and Oils

Aquatic devices that can work on both water and oils have great scientific and practical significance, but the challenge remains in developing novel materials with excellent repellence to both water and oils. Here, we report that an artificial "strider" can float on both water and oils by using supporting legs with ultraviolet (UV) switchable wettability. The legs were fabricated by immobilizing TiO2 nanoparticles and n-dodecanethiol onto copper foams via a simple mussel-inspired process. At ambient conditions, the strider floated freely on a water surface, but it dived in water and then stood stably at the interface of water/CHCl3 after UV illumination for 2 h. The reason for this unique behavior is that the legs changed their wettability from superhydrophobicity to underwater superoleophobicity after the illumination. It was revealed that the micro/nanohierarchical structures and photosensitivity of the immobilized TiO2 nanoparticles accounted for the switchable wettability and large supporting force of the legs. The findings of this study offer an alternative strategy for fabricating smart aquatic devices that might be used for water environment protection, water resource surveillance, oil spill cleanup, and so on.

Biomimetic mechanics behaviors of the strider leg vertically pressing water

Water striders capture the amazing feature to walk on water surface, and this phenomenon triggered extensive investigations in the past decades. We model the strider leg as a fiber vertically pressing into water surface and explore some striking mechanics behaviors in this process. First, the meniscus morphology is exactly solved by a numerical scheme. Based upon this solution, a non-dimensional parameter is defined in order to properly characterize the “capillary effect” of the objects with different volumes. The discussion of the buoyant force shows that the apparent contact angle has little impact on the variation of the water-supporting force. Besides this, there is no need for the strider leg to pierce into water, for the pinning of the triple contact line ensures a bigger buoyant force. In addition, the radius of the leg should be in an appropriate range to support the body weight. These analyses may cast light on how to design new-typed miniature aquatic devices.

Attempt toward a development of aquatic exercise device for gait disorders

Purpose: To develop an aquatic exercise device to facilitate locomotive motor output and achieve repetitive physiological gait patterns to improve movement dysfunctions. Methods: A custom designed leg movement apparatus (LMA) consisted of closed 4-linkage mechanisms and one-length changeable link using a spring. Three-dimensional motions and electromyographic (EMG) activities were recorded in eight healthy subjects to evaluate the reproducibility of the physiological gait patterns using the LMA with or without a spring apparatus in water. Results: Using the LMA with a spring apparatus compared to walking in water, the foot trajectories and the time course of the elevation angles in each lower limb joint kinematics were preserved. The time-series of the EMG showed reciprocal modulation between agonist and antagonist muscle groups in the hip and ankle joints. However, the amplitudes of the tibialis anterior muscle in the first half and rectus femoris in the last half of the movement cycle were reduced using the LMA with a spring apparatus. Conclusion: We developed a novel aquatic exercise device to reproduce physiological gait patterns. The LMA with a spring apparatus would be particularly valuable in therapy for movement dysfunctions to facilitate locomotive motor outputs.Implications for RehabilitationThe leg movement apparatus with spring for underwater use (LMA) would be effective gait training to induce the locomotor-like EMG activities.Hydrotherapy with the LMA has advantages over the partial body weight support treadmill training on land with a robotic device; (1) the LMA is electrically and mechanically safe, and (2) the LMA would require self-effort to generate the gait pattern for movement disorders, or also enable passive gait training by the physiotherapists.