Bio-inspired Approach Research Articles

Controlled engineering of tunable 3D-BiOX (X = Cl, Br) hierarchical nanostructures via dopamine-mediated synergetic interactions for efficient visible-light absorption photocatalysis

Integration of surface tunable 3D-BiOX hierarchical nanostructures (HNS) from size and facet controlled ultra thin 2D-nanosheets in aqueous solutions under an environmental benign process is remains a challenge. Because of their visible light response is highly depending on structural characteristics and yet most fabrications are involved hydrothermal methods. Herein, a simple dopamine-mediated bioinspired approach is proposed to integrate surface tunable 3D-BiOCl, 3D-BiOBr and 3D-BiOCl0.875Br0.125 hierarchical microspheres assembled by ultra thin 2D-nanosheets in aqueous solutions under mild conditions. The biomolecule dopamine (DA.HX) here played a multiple role as reactant, template and halogen source for 3D-BiOX materials, and its amount precisely controlled surface textural properties and nanosheets thickness with exposed (001) facets. Interestingly, the interfacial surface chelate interactions of dopamine facilitated the band-edge shift towards visible range along with surface induced oxygen defect impurities, which effectively reduced their forbidden bandwidth for extended visible light absorptions and photoluminescence quenching with an efficient charge separations. The photocatalytic activities of resulting 3D-BiOX HNS have shown excellent Rhodamine B degradation provided by highly oxidative h+ and surface induced oxygen vacancies acted as e- trapping centers to generate highly active O2− radicals for selective benzyl alcohol oxidation with high photostability and recyclability than their bare BiOX materials.

(Invited) Targeting Sustainability in Bioelectrochemical Systems for Water Quality Monitoring

Bioelectrochemical systems provide a sustainable approach to perform in-situ water quality monitoring, enabling the on-line detection of harmful contaminants in water samples. Specifically, interfacing intact microorganisms with abiotic electrodes allows developing bioelectrochemical systems for the early monitoring of several heavy metals and organic contaminants. Reports of microbial electrochemical sensors showed that a great number of contaminants can be monitored, achieving relevant sensitivity and stability.1 However, the sustainability of the utilized approaches, from biosensor setup to the choice of electrode materials, is not always considered, potentially limiting the applicability of the technology in the field.Here, focus is posed on the importance of targeting sustainability from the development to the application of microbial electrochemical sensors. Accordingly, a bio-inspired and bio-compatible approach for bacteria immobilization and redox mediation, as well as a bio-compatible route for electrode material development will be presented. Anoxygenic photosynthetic purple bacteria are utilized as the biophotocatalyst of choice, thanks to their extremely versatile metabolism where solar energy powers the oxidation of a broad variety of organic compounds. The use of these photosynthetic organisms is further motivated by their capability to cope and adapt to various environmental conditions (i.e., saline and non-saline environments, variable illumination conditions, presence of heavy metals)2, 3, making them of particular interest for applications in the field.4 Inspired by the natural approach utilized by mussels to obtain adhesive plaques, we explored an engineered deposition of polydopamine (PDA) for bacteria immobilization. The bio-inspired approach ensured firmly anchored purple bacteria on abiotic electrode surfaces while providing exogenous redox mediators to enhance photoexcited electrons harvesting. Focusing on the electrode material, we investigated the use of polyhydroxylkanoates (PHAs), biopolymers accumulated by a number of microorganisms, as biopolymer matrix to obtain homogeneous, flexible and free-standing electrodes. The coupling of these electrodes with photosynthetic bacteria for biophotoanodes development will be discussed, presenting advantages as well as future possibilities and challenges. References Chen, H.; Simoska, O.; Lim, K.; Grattieri, M.; Yuan, M.; Dong, F.; Lee, Y. S.; Beaver, K.; Weliwatte, S.; Gaffney, E. M.; Minteer, S. D. Chem. Rev. 2020, 120, 12903-12993.Giotta, L.; Agostiano, A.; Italiano, F.; Milano, F.; Trotta, M. Chemosphere 2006, 62, 1490-9.Gaffney, E. M.; Grattieri, M.; Beaver, K.; Pham, J.; McCartney, C.; Minteer, S. D. Electrochim. Acta 2020, 337, 135731.Grattieri, M. Photochem. Photobiol. Sci. 2020, 19, 424-435.

InsideOut: A Bio-Inspired Machine Learning Approach to Estimating Posture in Robots Driven by Compliant Tendons.

Estimates of limb posture are critical for controlling robotic systems. This is generally accomplished with angle sensors at individual joints that simplify control but can complicate mechanical design and robustness. Limb posture should be derivable from each joint's actuator shaft angle but this is problematic for compliant tendon-driven systems where (i) motors are not placed at the joints and (ii) nonlinear tendon stiffness decouples the relationship between motor and joint angles. Here we propose a novel machine learning algorithm to accurately estimate joint posture during dynamic tasks by limited training of an artificial neural network (ANN) receiving motor angles and tendon tensions, analogous to biological muscle and tendon mechanoreceptors. Simulating an inverted pendulum—antagonistically-driven by motors and nonlinearly-elastic tendons—we compare how accurately ANNs estimate joint angles when trained with different sets of non-collocated sensory information generated via random motor-babbling. Cross-validating with new movements, we find that ANNs trained with motor angles and tendon tension data predict joint angles more accurately than ANNs trained without tendon tension. Furthermore, these results are robust to changes in network/mechanical hyper-parameters. We conclude that regardless of the tendon properties, actuator behavior, or movement demands, tendon tension information invariably improves joint angle estimates from non-collocated sensory signals.

Nonmonotonic Coupled Dissolution‐Precipitation Reactions at the Mineral–Water Interface

AbstractDissolution is inherent to fluid‐mineral systems. Yet its impact on minerals reacting with electrolytes is overlooked. Here, a novel nonmonotonic behavior for the surface interactions of carbonates (calcite and Mg‐calcite) with organic acids is reported. Applying a bioinspired approach, Mg‐calcite sensors via amorphous precursors, avoiding any preconditioning with functional groups are synthesized. A quartz crystal microbalance is used to study the mass changes of the mineral on contact with organic acids under varying ionic conditions, temperatures, and flow velocities. Supported by confocal Raman microscopy and potentiometric titrations, nonmonotonous mass developments are found as a function of Ca2+concentration and flowrate, and attributed to three coupled chemical reactions: i) carbonate dissolution via Ca2+ion complexation with organic molecules, and the formation of organo‐calcium compounds as ii) a surface phase at the mineral–water interface, and iii) particles in the bulk fluid. These processes depend on local ion contents and the precipitation onset (i.e., saturation index) of organo‐calcium salts, both of which substantially differ in the bulk fluid and in the fluid boundary layer at mineral interfaces. This continuum between dissolution and precipitation provides a conceptual framework to address reactions at mineral interfacial across disciplines including biomineralization, ocean acidification and reservoir geochemistry.

Fumaria officinalis-assisted synthesis of Manganese nanoparticles as an anti-human gastric cancer agent

Regarding applicative, facile, green chemical research, a bio-inspired approach is being reported for the synthesis of Mn nanoparticles by Fumaria officinalis as a natural reducing/stabilizing and solid support agent without using any toxic and harmful reagent. The MnNPs were synthesized using an aqueous extract of Fumaria officinalis. The formation and morphology of the nanoparticles were evaluated using different techniques including fourier-transform infrared spectroscopy (FTIR), UV–Visible spectroscopy, X-ray diffraction analysis (XRD), scanning electron microscope (SEM), and energy dispersive X-ray analysis (EDX) analysis. The properties of Fumaria officinalis leaf aqueous extract and MnNPs against common human gastric cancer cell lines i.e. KATOIII, NCI-N87, and SNU-16 were studied. The results show the successful formation of MnNPs with a spherical morphology with an average size of 50.05 nm. The viability of malignant human gastric cell line reduced dose-dependently in the presence of Fumaria officinalis leaf aqueous extract and MnNPs. After the clinical study, MnNPs can be utilized as an efficient drug in the treatment of human gastric cancer in humans.

Adjustable Compliance and Force Feedback as Key Elements for Stable and Efficient Hopping

Achieving efficient and human-like hopping motions with consistent consecutive patterns requires proper mechanical design and control. In this regard, we introduce a new bioinspired design and control approach comprised of a hybrid actuation system and force-based compliance control. Combining an electric motor with a pneumatic artificial muscle makes up the so-called Electric-Pneumatic Actuation (EPA) system which enables presetting the leg compliance. Using the ground reaction force for online adjustment of EPA allows controlling the leg stiffness. This approach combines a simplified version of reflex-based control and physical impedance adjustment, that resembles the human neuromuscular system in a parsimonious way. By optimizing PAM pressures and control gains for different targeted hopping heights using Bayesian optimization, we show experimentally that the proposed approach generates various stable hopping motions and yields efficient performance. Moreover, our method is shown to be capable of creating more human-like hopping patterns compared to the previous studies on the same robot.

Engineering nanocluster arrays on lotus leaf as free-standing high areal capacity Li-ion battery anodes: A cost-effective and general bio-inspired approach

Bio-inspired materials have received broad attention for energy-storage systems owing to their special properties and low cost. Here, a cost-effective and general strategy is developed for preparing nanocluster arrays on leaves as three-dimensional free-standing Li-ion battery anodes. As a demonstrating case study, an FeCo2O4 nanocluster array is constructed on lotus leaf, which displays a high areal capacity of 2.4 mAh cm−2 after cycling 100 times, and a stable Coulombic efficiency of 99.9%. After long-term 900 cycles at 10 ºC, capacity remains 1.15 mAh cm−2. At a high temperature of 45 ºC, capacity keeps 1.95 mAh cm−2 after cycling 150 times. A recoverable rate-performance after three-rounds measurements is also achieved, enabling the anode to be potentially used at different conditions. In addition, the preparation approach is successfully used for making many other composites including ZnCo2O4, NiCo2O4, CuCo2O4 nanocluster arrays on lotus leaves, and ZnCo2O4, NiCo2O4, CuCo2O4, FeCo2O4 nanocluster arrays on bamboo leaves, displaying a good applicability.

Contact and Physical Interaction

This article reviews approaches to controlling robots undergoing physical contact and dynamic interaction with objects in the world. Conventional motion control is compared with a hybrid combination of position and force control. Several challenges are reviewed, most importantly the problems of instability: dynamic instability due to coupling, and static instability due to exerting force. Energetically passive interactive dynamics addresses the former; a minimum stiffness proportional to the force exerted addresses the latter. Actuators, which dominate the robot's interactive dynamics, are briefly surveyed, including series elastic, variable-stiffness, and emerging designs. A comparison with human performance is made. A bioinspired approach to controlling interactive dynamics (mechanical impedance or admittance) is reviewed. Robot configuration profoundly modulates apparent inertia, whereas force feedback control has minimal influence. Superimposing first-order mechanical impedances simplifies controlling many degrees of freedom. It manages redundancy while preserving passivity (unlike null-space projection methods) and enables seamless operation into and out of singular configurations.

Auto-QCLF: A Quick and Reliable EEG Lead Field Quality Control for Big Databases

With regards to applied, facile, green chemical research, a bio-inspired approach is being reported for the synthesis of Au NPs by using Tribulus terrestris extract. The innate oxygenated phytochemicals facilitated the green reduction of Au3+ ions to corresponding NPs and also stabilized them by encapsulating them. This modification prevented the as-synthesized Au NPs towards agglomeration and tiny NPs were obtained in uniformly spherical in shape and in the range of 10–15 nm dimension. Physicochemical characteristics of the green synthesized Au NPs were evaluated by advanced physicochemical techniques like UV–Vis and FT-IR spectroscopy, SEM, TEM, EDX and XRD study. Catalytic performance of the biomolecule functionalized Au NPs was investigated in the controlled and selective oxidation of sulfides to sulfoxides using hydrogen peroxide as green oxidant at room temperature. Aromatic, aliphatic and heterocyclic sulfides were oxidized to their corresponding sulfoxides with high yields without formation of over oxidized sulfones. The catalyst was easily recovered and recycled for 8 successive times without noticeable decrease in catalytic activity. In addition, the biosynthesized Au NPs indicated suitable antioxidant and anti-acute leukemia properties against THP-1 cell line. Tribulus terrestris extract and the green synthesized Au NPs exhibited a maximum DPPH scavenging activity of 78% and 29.37%, respectively. Again, in the anticancer studies over THP-1 cell line following MTT assay, the Au NP exhibited gradual reduced % cell viability with increase in its concentration. At an Au NPs concentration of 2000 µg/mL, the % toxicity became maximum suggesting efficient inhibition of cancer invasion. Based on the above results, Au NPs-Tribulus could be administered as a potential anti-leukemia drug for the treatment of acute leukemia following the clinical trial studies in humans.

Bioinspiration as a method of problem-based STEM education: A case study with a class structured around the COVID-19 crisis.

Bioinspiration is a promising lens for biology instruction as it allows the instructor to focus on current issues, such as the COVID‐19 pandemic. From social distancing to oxygen stress, organisms have been tackling pandemic‐related problems for millions of years. What can we learn from such diverse adaptations in our own applications? This review uses a seminar course on the COVID‐19 crisis to illustrate bioinspiration as an approach to teaching biology content. At the start of the class, students mind‐mapped the entire problem; this range of subproblems was used to structure the biology content throughout the entire class. Students came to individual classes with a brainstormed list of biological systems that could serve as inspiration for a particular problem (e.g., absorptive leaves in response to the problem of toilet paper shortages). After exploration of relevant biology content, discussion returned to the focal problem. Students dug deeper into the literature in a group project on mask design and biological systems relevant to filtration and transparency. This class structure was an engaging way for students to learn principles from ecology, evolution, behavior, and physiology. Challenges with this course design revolved around the interdisciplinary and creative nature of the structure; for instance, the knowledge of the participants was often stretched by engineering details. While the present class was focused on the COVID‐19 crisis, a course structured through a bioinspired approach can be applied to other focal problems, or subject areas, giving instructors a powerful method to deliver interdisciplinary content in an integrated and inquiry‐driven way.

Global optimisation in Hilbert spaces using the survival of the fittest algorithm

Global optimisation problems in high-dimensional and infinite-dimensional spaces arise in various real-world applications such as engineering, economics and finance, geophysics, biology, machine learning, optimal control, etc. Among stochastic approaches to global optimisation, biology-inspired methods are currently very popular in the literature. Bio-inspired approaches imitate natural ecological and evolutionary processes and are reported to be efficient in a large number of practical study cases. However, many bio-inspired methods can possess some vital drawbacks. For example, due to their semi-empirical nature, convergence to the globally optimal solution cannot always be guaranteed. Another major obstacle is that the existing methods often struggle with higher dimensionality of the space of parameters, which results in a slow convergence. Moreover, it is often difficult to adjust the dimensionality of the space of parameters in the corresponding computer code for a practical realisation of the optimisation method. Here, we present a bio-inspired global stochastic optimisation method applicable in Hilbert function spaces. The proposed method is an evolutionary algorithm inspired by the Darwin’s famous idea of survival of the fittest and is, therefore, referred to as the ‘Survival of the Fittest Algorithm’ (SoFA). Mathematically, the convergence of SoFA is a consequence of the fundamental property of localisation of probabilistic measure in a Hilbert space and we rigorously prove the convergence of the introduced algorithm for a generic class of functionals. The approach is simple in terms of practical coding. As an insightful, real-world problem, we apply our method to find the globally optimal trajectory for the daily vertical migration of zooplankton in the ocean and lakes, this phenomenon is considered to be the largest synchronised movement of biomass on Earth. We maximise fitness in a function space derived from a von-Foerster stage-structured population model with biologically realistic parameters. We show that for problems of fitness maximisation in high-dimensional spaces, SoFA provides better performance as compared to some other stochastic global optimisation algorithms. We highlight the links between the new optimisation algorithm and natural selection processes in ecosystems occurring within a population via gradual exclusion of competitive con-specific strains.

The Fruit of Gold: Biomimicry in the Syntheses of Lankacidins.

Natural products are constructed by organisms in impressive ways through various highly selective enzyme-catalyzed chemical reactions. Over the past century, there has been considerable interest in understanding and emulating the underlying biosynthetic logic for the target molecule. The successful implementation of a biomimetic strategy usually has some uniquely valuable benefits over other abiotic routes in total synthesis by (1) corroborating the chemical feasibility of a given biogenetic hypothesis and further unraveling some insightful implications for future biosynthetic studies and (2) providing remarkably more concise access to not only the original synthetic target but also diversified biogenetically related congeners, which may result in either the structural reassignment of previously disclosed natural products or the anticipation of undiscovered natural products. However, for the devised essential biomimetic transformation, fine-tuning the optimization of the substrates and the reaction conditions can sometimes be painstakingly challenging. Turning to nature for inspiration can provide additional impetus for methodological innovations.Previously used as oral veterinary drugs, lankacidins have potential as next-generation antibiotics to tackle the problems caused by multidrug-resistant bacteria with novel modes of action (MoAs). The hypersensitive and densely functionalized lactonic core within this family of macrocyclic polyketides poses a formidable challenge for chemical total synthesis and derivatization. In this account, we summarized the evolution of a unified biomimetic approach toward 10 lankacidin antibiotics and their linear biosynthetic intermediates in the longest linear 7-12 steps from readily available starting materials. Our endeavor commenced with an intermolecular bioinspired amido sulfone-based Mannich reaction approach to assemble 2 advanced fragments under mild biphasic organocatalytic conditions. It successfully gave rise to stereodivergent access to 4 C2/C18-isomeric lankacyclinols but failed to efficiently deliver lactone-containing congeners through Stille macrocyclization. Facilitated by the thermolysis chemistry of N,O-acetal to generate the requisite N-acyl-1-azahexatriene species, we realized the projected Mannich macrocyclization and eight macrocyclic lankacidins can be produced by orchestrated desilylative manipulations. In this process, we were able to perform structural reassignments of isolankacidinol (7 to 50) and isolankacyclinol (104 to 83) and, for the first time, elucidate the natural occurrence of 2,18-bis-epi-lankacyclinol (84). Moreover, the inability of the current biomimetic route to cofurnish the reported structure of 2,18-seco-lankacidinol A (15) triggered a proposed structural revision that is rooted in reconsidered biogenesis and was confirmed by a divergent synthesis that enabled us to identify the correct isomer (116). Finally, the modular, diversity-oriented design also provided streamlined entries to acyclic 2,18-seco-lankacidinol B (120) and the biosynthetic intermediate LC-KA05 (17) together with its C7-O-deacetylated congeners in all C4/C5-stereochemical variations (18, 127-129), culminating in a need for structural revision to the six-membered lactonic segment in LC-KA05-2. The selection and execution of biomimetic strategies in lankacidin total synthesis give rise to all the previously mentioned advantages at the current stage. The modular-based, late-stage diversified complex construction offers an exceptionally high level of synthetic flexibility for future synthetic forays toward newly isolated or chemically modified congeners within the lankacidin family.

A bioinspired approach to fabricate fluorescent nanotubes with strong water adhesion by soft template electropolymerization and post-grafting

HypothesisIn this original work, we aim to control both the surface wetting and fluorescence properties of extremely ordered and porous conducting polymer nanotubes prepared by soft template electropolymerization and post-grafting. For reaching this aim, various substituents of different hydrophobicity and fluorescence were post-grafted and the post-grafting yields were evaluated by surface analyses. We show that the used polymer is already fluorescent before post-grafting while the post-grafting yield and as a consequence the surface hydrophobicity highly depend on the substituent. ExperimentsHere, we have chosen to chemically grafting various fluorinated and aromatic substituents using a post-grafting in order to keep the same surface topography. Flat conducting polymer surfaces with similar properties have been also prepared for determining the surface energy with the Owens-Wendt equation and estimating the post-grafting yield by X-ray Photoemission Spectroscopy (XPS) and Time of Flight Secondary Emission Spectrometry (ToF-SIMS). For example, using fluorinated chains of various length (C4F9, C6F13 and C8F17), it is demonstrated that the surface hydrophobicity and oleophobicity do not increase with the fluorinated chain length due to the different post-grafting yields and because of the presence of nanoroughness after post-grafting. FindingsThese surfaces have high apparent water contact angle up to 130.5° but also strong water adhesion, comparable to rose petal effect even if there are no nanotubes on petal surface. XPS and ToF-SIMS analyses provided a detailed characterisation of the surface chemistry with a qualitative classification of the grafted surfaces (F6 > F4 > F8). SEM analysis shows that grafting does not alter the surface morphology. Finally, fluorescence analyses show that the polymer surfaces before post-treatment are already nicely fluorescent. Although the main goal of this paper was and is to understand the role of surface chemistry in tailoring the wetting properties of these surfaces rather than provide specific application examples, we believe that the obtained results can help the development of specific nanostructured materials for potential applications in liquid transport, or in stimuli responsive antimicrobial surfaces.

Domino Reaction Encoded Heterogeneous Colloidal Microswarm with On‐Demand Morphological Adaptability

Emulating natural swarm intelligence with group-level functionality in artificial micro/nanorobotic systems offers an opportunity to sublimate the limited functions of individuals and revolutionize their applications. However, achieving synchronous operation of microswarms with environmental adaptability and cooperative tasking capability remains a challenge. Here, an adaptive and heterogeneous colloidal magnetic microswarm with domino reaction encoded cooperative functions is presented. Through programming external magnetic fields, the system self-organizes into two swarm states, that is, vortex and ribbon microswarms, which can switch between each other reversibly within seconds, allowing to traverse tortuous, branched, and confined environments through adaptive morphological transformation. By specializing subgroups of building blocks with separate functions, cooperative tasking capability is integrated into the heterogeneous system following a "division of labor" manner. Given targeted therapy as a proof-of-concept task, the coordinated delivery of heterogeneous colloidal system across a complex environment with an access rate higher than 90% is demonstrated, and the specialization and cooperation between building blocks to disrupt multiple growth pathways of cancer cells via domino reaction are realized. The reconfigurable microswarm with hierarchical functionality presents a bioinspired approach to adapt to environmental variations and address multitasking requirements, which advances the development of microrobotic swarms and promises major benefits in biomedical fields.

Time-varying Black–Litterman portfolio optimization using a bio-inspired approach and neuronets

The Black–Litterman model is a very important analytical tool for active portfolio management because it allows investment analysts to incorporate investor’s views into market equilibrium returns. In this paper, we define and study the time-varying Black–Litterman portfolio optimization under nonlinear constraints (TV-BLPONC) problem as a nonlinear programming (NLP) problem. More precisely, the nonlinear constraints refer to transaction costs and cardinality constraints. Furthermore, a speedy weights-and-structure-determination (WASD) algorithm for the power-activation feed-forward neuronet (PFN) is presented to solve time-series modeling and forecasting problems. Inhere, the investor’s views in the TV-BLPONC problem are considered as a forecasting problem and, thus, they are produced by the WASD-based PFN. In addition, using the beetle antennae search (BAS) algorithm a computational method is introduced to solve the TV-BLPONC problem. For all we know, this is an innovative approach that integrates modern neural network and meta-heuristic optimization methods to provide a solution to the TV-BLPONC problem in large portfolios. Our approach is tested on portfolios of up to 90 stocks with real-world data, and the results show that it is more than 30 times faster than other methods. Our technique’s speed and precision are verified in this way, showing that it is an outstanding alternative to ordinary methods. In order to support and promote the findings of this work, we have constructed two complete MATLAB packages for the interested user, which are freely available through GitHub.

Thermally stimulated artificial muscles: Bio-inspired approach to reduce thermal deformation of ball screws based on inner-embedded CFRP

Abstract Ball screws are the indispensable machine tool components and, as such, influence the positional accuracy of machine tools. The accuracy stability of machine tools is affected by thermal deformation of ball screws resulting from the increase in temperature. Inspired by the distinctive artificial muscle heat behavior, a bio-inspired ball screw was proposed. The proposed ball screw was based on the inner-embedded carbon fiber-reinforced plastic (CFRP), which restrains the axial expansion through the thermal contraction of CFRP. Additionally, a thermal conductor was mounted between the screw shaft and CFRP to improve the thermal conduction condition. Furthermore, both the simulation analysis and comparative experiments were carried out to compare the bio-inspired ball screw with the standard one. Two working conditions were considered to evaluate the effectiveness of the novel design, primarily in terms of reducing thermal deformation. Both results show that the proposed approach is effective and can be applied to reduce the thermal deformation of ball screws.

Highly conjugated carbazole-based monomers for the control of nanotubular surface structures by soft template electropolymerization

Abstract In this work, a bioinspired approach is used to prepare nanotubular structures with tunable hydrophobicity and water adhesion by a soft template surfactant-free electropolymerization in organic solvent. Various highly conjugated carbazole-based molecules are used as monomer. The presence of water in the organic solvent enables the formation of porous and rough nanostructures. Their shapes depend essentially on the nature of the monomer and the way it polymerizes. Various morphologies were obtained from nanoparticles network to horizontally or vertically aligned nanotubes. The nanostructured surfaces reach superhydrophobic properties and their dynamical behavior varies with the monomer from sticky to slippery. For example, using 9,3′:6′,9″-tercarbazole (TC) very long nanotubes are observed but their number is higher at constant potential. At high deposition charge, it is observed that most of the tubes are even collapsed leading to a strong increase of surface hydrophobicity with apparent contact angle up to 143° with strong water adhesion comparable to rose petals or gecko foot.

Green synthesis of gold nanoparticles (Au NPs) using Tribulus terrestris extract: Investigation of its catalytic activity in the oxidation of sulfides to sulfoxides and study of its anti-acute leukemia activity

With regards to applied, facile, green chemical research, a bio-inspired approach is being reported for the synthesis of Au NPs by using Tribulus terrestris extract. The innate oxygenated phytochemicals facilitated the green reduction of Au3+ ions to corresponding NPs and also stabilized them by encapsulating them. This modification prevented the as-synthesized Au NPs towards agglomeration and tiny NPs were obtained in uniformly spherical in shape and in the range of 10–15 nm dimension. Physicochemical characteristics of the green synthesized Au NPs were evaluated by advanced physicochemical techniques like UV–Vis and FT-IR spectroscopy, SEM, TEM, EDX and XRD study. Catalytic performance of the biomolecule functionalized Au NPs was investigated in the controlled and selective oxidation of sulfides to sulfoxides using hydrogen peroxide as green oxidant at room temperature. Aromatic, aliphatic and heterocyclic sulfides were oxidized to their corresponding sulfoxides with high yields without formation of over oxidized sulfones. The catalyst was easily recovered and recycled for 8 successive times without noticeable decrease in catalytic activity. In addition, the biosynthesized Au NPs indicated suitable antioxidant and anti-acute leukemia properties against THP-1 cell line. Tribulus terrestris extract and the green synthesized Au NPs exhibited a maximum DPPH scavenging activity of 78% and 29.37%, respectively. Again, in the anticancer studies over THP-1 cell line following MTT assay, the Au NP exhibited gradual reduced % cell viability with increase in its concentration. At an Au NPs concentration of 2000 µg/mL, the % toxicity became maximum suggesting efficient inhibition of cancer invasion. Based on the above results, Au NPs-Tribulus could be administered as a potential anti-leukemia drug for the treatment of acute leukemia following the clinical trial studies in humans.

Bio-inspired cluster–based optimal target identification using multiple unmanned aerial vehicles in smart precision agriculture

Farming is the major profession in several republics for centuries. However, due to the immigration of individuals from rural to urban, there is prevention in farming. The use of modern technology in the precision agriculture field increases productivity and also improves the exports of a country. The productivity may suffer due to different environmental factors, diseases and insects attacks on the crops, especially tomatoes. The target area (i.e. the affected crops area due to environmental factors) identification and delivery of timely information about diseases in the crops to the ground station are mandatory to make the precautionary measurements. In flying sensor networks, the localization and clustering of multiple unmanned aerial vehicles for target areas identification is a challenging task due to energy constraints, communication range, frequent change in topology, link expiration and high mobility. In this article, we proposed the localization and clustering of multiple unmanned aerial vehicles for the identification of affected target areas in the tomato crop field. The localization of unmanned aerial vehicles depends on the weights of environmental factors, that is, relative humidity, soil moisture, temperature, light intensity, NPK (nitrogen (n), phosphorus (p) and potassium (k)) and power of hydrogen (pH). A honey bee optimization approach is used for the localization and formation of multiple unmanned aerial vehicles’ cluster to accurately identify the target areas. The performance of our bio-inspired approach is compared in terms of communication overhead, packet delivery ratio, mean end-to-end delay and energy consumption with the existing swarm intelligence–based schemes and validated via a simulation. The simulation result shows that the bio-inspired approach performs better among the selected approaches.

Use of a MEMS Differential Pressure Sensor to Detect Ground, Ceiling, and Walls on Small Quadrotors

Effective autonomous indoor flight requires an ability to sense and navigate ground, ceiling, and walls. While this can be accomplished in many ways including vision, one bio-inspired approach that is not well studied uses the detection of pressure changes when flying close to surfaces. As an example, an increase in pressure can be detected when a quadrotor flies close to the ground, a phenomenon known as ‘ground effect’. This work evaluates the viability of differential pressure measurements as a means of sensing ground, ceilings, and walls for small quadrotors. Extending existing models for thrust in ground effect, a model is derived to predict pressure changes due to ground effect in hover and tilt. The pressure response with ground effect is characterized across a range of distances, thrust levels, sensor locations, and quadrotor tilts using a Crazyflie 2.0 quadrotor and a small MEMS differential pressure sensor. Characterization experiments are also used to evaluate pressure measurements at varying distances from ceilings and walls, as well as the pressure behavior due to step changes in ground height. Manually controlled free flight tests are used to validate ground sensing in both nominal and visually challenging environments, as well as wall sensing in free flight.