Plants are ideal for soft robot design due to their favourable ability to adapt and respond to the environment. Here, three different motile plants, bird of paradise (Strelitzia reginae), the waterwheel plant (Aldrovanda vesiculosa), and the Venus flytrap (Dionaea muscipula), are introduced. They may deform following the physics predetermined by the structure. As a decentralised species, plants respond under environmental stimulation without a controlling unit like a brain and motor-like muscles. The mechanism behind the movement of the plant should enlighten more intelligent robotics. In this study, movable plants are compared for their actuating principle, and, based on their deformation model, three pneumatic actuators are designed. The bird of paradise opens its petals when the sunbirds sit on another petal, which inspires the structure utilising the bending of the midrib to open lobes. Similarly, the waterwheel plant stores energy in the bending midrib and releases it when it closes. But, the Venus flytrap takes advantage of snapping to achieve rapid closure. Using three-dimensional (3D) printing, pneumatic actuators, which are ruled by the mechanism of plants with silicon rubber surfaces, are fabricated and tested. Under air pressure, the actuator deforms, mimicking the plant cells expanding under the turgor pressure. The hingeless actuator performs well while interacting with dedicated projects.

Tooth enamel, vulnerable to various harmful factors, often undergoes demineralization. Combating enamel destruction typically involves replenishing demineralized areas with non-native calcium sources, which poses challenges for effective remineralization. Aspartic acid (Asp) can participate in the crystallization process of hydroxyapatite, improving its structural order and thereby helping to restore and strengthen enamel. The aim of the investigations was to determine the effect of Asp on the remineralization of a bovine enamel block in vitro. Enamel blocks were sectioned from bovine teeth, and the baseline surface microhardness (SMHR) of the samples was measured. After demineralization in a solution at pH 4.5 for 60 minutes, SMHR was remeasured. Ten enamel samples per group were treated with respective solutions for 16 hours at pH 6.5. The percentage of SMHR achieved through the treatments was calculated and used to compare the ability to repair demineralized enamel samples. Three investigations with the same design were conducted. The initial experiment indicated that 1% hydroxyapatite facilitated enamel remineralization, achieving a significant mean increase in surface microhardness (22.99±10.43; p<0.05) compared with that of the negative control, deionized water, which showed a mean decrease (-1.87±17.11; p<0.05). However, this remineralization was not superior to that induced by the fluoride positive control (35.56±23.41; p<0.05). Subsequently, the second experiment established that 0.5% aspartic acid significantly reduced enamel microhardness (-37.32±24.64; p<0.05), indicating a pronounced demineralizing effect when compared with both deionized water (-17.52±23.54; p<0.05) and fluoride (14.12±13.40; p<0.05). The third experiment demonstrated that the combination of 0.5% aspartic acid with 1% hydroxyapatite significantly enhanced remineralization (33.08±14.84; p<0.05), outperforming the fluoride-positive control (5.15±4.84; p<0.05) as well as deionized water (-29.21±18.38; p<0.05). In conclusion, while aspartic acid alone may lead to enamel demineralization, its combination with hydroxyapatite shows promise in surpassing fluoride's remineralizing efficacy, highlighting a potential synergistic approach for dental treatments.

In our work, we chose chitosan (polysaccharide) as a template for the synthesis of mesoporous silica-based material (ZChM). Both acidic and slightly alkaline synthesis conditions were tested. In the acidic method, we varied the molecular weight of chitosan (200 and 500 Da) and the time of TEOS addition.

Biomimetic silica samples (ZChM-series) were characterized using TEM, XRD, BET, and TG/DTA methods. According to the obtained data, a material with a more ordered structure was achieved by using an acidic type of synthesis with chitosan 200Da and a controlled rate of TEOS addition. This material has a surface area of around 790 m2/g, which is only is 30% less than the surface area of MCM-41-type materials. The material synthesized in alkaline conditions has a significantly lower specific surface area. In addition to the surface area, the synthesis conditions also affected the pore size of the resulting materials—the material obtained under alkaline conditions has the largest pore diameter (6,64 nm), while the second sample synthesized in an acidic environment (ZChM-2a) has a slightly lower pore diameter than MCM-41, 2.73 vs. 3.3 nm, respectively.

The new bioinspired silica samples were tested as adsorbents of water-soluble amino acids, and both kinetics and adsorption equilibrium were studied. It was found that synthesis conditions can significantly affect the sorption properties of mesoporous silica. The biomimetic silica synthesized with chitosan as a template in an acidic medium (ZChM-1a) can sorb tryptophan and phenylalanine. Otherwise, material ZChM-1s (synthesized in an alkaline medium) does not practically sorb these amino acids.

Thus, chitosan can be successfully used as a template for the synthesis of mesoporous silica. By varying the medium conditions, the molecular weight of chitosan, and the rate of addition of TEOS, it is possible to obtain mesoporous materials with different surface and adsorption properties.

We use electrochemical additive manufacturing method to combine cicada-inspired nanostructures and fluoridated hydroxyapatite (FHA) solutions, and give full play to their physical and chemical antibacterial advantages. We prepared cicada-inspired fluoridated hydroxyapatite nanostructured surfaces on the surface of acid etched titanium for the first time. It consists of closely aligned single FHA nanopillars. The diameter of a single FHA nanopillar is about 65-95 nm, the height is about 380-510 nm, and the aspect ratio is about 4.5-7. It has high crystallinity, long-range regularity and defect free lattice with the [0001] (i.e. [001], c-axis) crystallographic orientation. It is expected to be applied to orthopedic and dental implant surgery in the future.

Introduction: With the rapid development of modern medicine, implant surgery has gradually become more important. However, due to the use of antibiotics, the bacterial infection of implantation becomes difficult to overcome. Therefore, we urgently need to find non-antibiotic antibacterial methods. Recently, cicada-inspired nanostructures and fluoridated hydroxyapatite (FHA) solutions have attracted great interest for their remarkable bactericidal ability. But cicada-inspired nanostructures are not resistant to Gram-positive bacteria. In this study, we aimed to develop fabricating nano-structures with bioactive and biocompatible properties.

Results & Discussion: The cicada-inspired FHA nanostructure deposition layer was successfully formed on an AETi plate of which size is 9 × 9 × 1 mm. It consists of closely aligned single FHA nanopillars. The diameter of a single FHA nanopillar is about 65-95 nm, the height is about 380-510 nm, and the aspect ratio is about 4.5-7. The fluorine concentration (2.22 at.%) and Ca/P ratio (1.61) are similar to those of the Ca₁₀(PO₄)₆(OH)F (fluorine concentration = 2.33 at.%, Ca/P = 1.67).

Conclusions: This study provide a novel, economical and time-saving method to prepare cicada-inspired nanostructured surfaces, which may enhance the antibacterial activity of orthopedic and dental implants and lay the foundation for better biological applications in the future.

1. Introduction. For attachment and propulsion generation during locomotion, different surface adaptations have been evolved in the course of animal evolution. Some of these structures have been well structurally studied, but their functional mechanisms, based on the interplay between the ultrastructure, material properties and physical interactions remained unresolved until recently. The reason for this is that such research requires approaches of several disciplines: zoology, structural biology, biomechanics, physics, and surface science. In addition to the use of a wide variety of microscopy techniques, we established a set of experimental designs that allows obtaining information about adhesive and frictional properties, as well as local and global mechanical properties of materials of animal attachment devices (part 1) and belly surface of the snake skin (part 2), in order to understand tribological mechanisms behind these biological surfaces.

2. Attachment: flies, spiders, geckos on the ceiling. In order to show different functional principles, we experimentally tested about 600 different locomotory attachment devices on legs of insects (Figure 1), spiders and geckos and tried to outline general rules of the interrelationship between their structure and function. Since these broad comparative studies include a wide variety of organisms, some questions about the evolution of these systems could be resolved.

3. Snake skin tribology. Owing to the lack of extremities, the ventral body side of snakes is in almost continuous contact with the substrate. In spite of this, snakes are one of the most successful animal groups in occupying various ecological niches. From a tribology point of view, their ventral skin surface has to fulfill two opposite functions: (1) to support body propulsion during locomotion by generating high friction in contact with the substrate and (2) to reduce skin material abrasion by generating low friction in forward sliding along the substrate.

The flying wing of the beetle exhibits unique wing spreading–flying–collecting behavior in the process of flight, which is the best bionic object for flapping wing aircraft design. In this paper, through the motion behavior observation system, the behavior analysis of beetle spreading–flying–unfolding wings is carried out, the kinematic parameters of the whole flight process are obtained, and the flow field visualization of the above behavior is studied using the smoke line method. During the flapping process, the flying wing of the beetle is spread out one by one in two stages, and the wingtip trajectory is in the shape of "W" when the wing is folded. The unique microhair structure on the sheath wing can provide sufficient friction to facilitate the folding of the flying wing. When flying, the wingtip trajectory of the beetle is in the shape of "8", and the flying wing is deformed in the process of downstroke and supination, which provides additional unsteady lift for the beetle flight. The enhanced leading edge vortex and surrounding leading edge vortex produced during the upstroke and downroke further reveal the unique high-lift mechanism of beetle flight. Based on the above research on the flight mechanism of the beetle, a flapping-wing aircraft imitating the beetle is designed.

The concept of green construction enables a revolutionary change in the construction sector in terms of design, production, and management. One such method is introducing the concept of biomimicry. Biomimicry is utilized in the field of design to solve problems. This paper mainly discusses about the mimicking of human skeleton for structural design. The idea is based on mimicking humerus bone as a tension member and femur bone as a compression member. The optimized members of compression and tension (strut and tie) were put together to form the mimicked king post truss analytically with the conventional cross section truss. Three cases were considered analytically with the average diameter, maximum diameter, and equivalent self-weight to the members of mimicked truss. Experimentally testing was also conducted with the non-destructive test and the point load test. The result shows that the ultimate load carrying capacities of the critical compression member and the tension member were 846.16 kN and 1952 kN, respectively. Meanwhile, the achieved loads were 780.30 kN and 1729 kN. Also, the ratio of analytical stiffness to self-weight was 21.83 mm^-1 and the ratio of experimental stiffness to self-weight was 19.15 mm^-1. Therefore, from the results, it was observed that the equivalent results for mimic truss can be achieved in a truss which is modeled of the equivalent self-weight. Hence, the development and use of structural elements using biomimicry is feasible and will lead to economic, green, and energy efficient structures.

It is well known that some living organisms use different adaptation mechanisms to survive and thrive¹. One of the outstanding examples of adaptation are marine gastropod mollusks Elysia marginata and Elysia atroviridis (sea slags)². After being decapitated, these living organisms have an ability not only to survive but also to revive and grow again. These invertebrates inspire us to conduct a modification of carbon nanoparticles (CNPs) containing Csp²-hybridized carbons using cyclooligosiloxanes containing redox-active metallocenes. In the CNP modification, the cyclooligosiloxanes containing redox-active metallocenes at first lose some of their parts (cyclopentadienyl ring) in the presence of the catalytic mixture, and coordinate to a wall of CNPs. Then, these cyclooligosiloxanes undergo cationic ring opening polymerization catalysis by one of the components of the catalytic mixture, and a polysiloxane chain grows.

The successful modification of CNPs using (poly)siloxanes containing redox-active metallocenes was confirmed by means of Raman and X-Ray photoelectron spectroscopies and transmission electron microscopy. The modified CNPs have good compatibility with the polysiloxane matrix and an improved distribution in it.

In this mollusk-inspired modification of CNPs, along with the grafting of the polysiloxane chain on the surface of carbon nanotubes, we introduced redox-active centers on the surface of the CNPs. This, in turn, significantly broadened the application of the modified CNPs as promising components of electrochemical sensors, biosensors³ and energy storage devices⁴.

The authors acknowledge St Petersburg State University for a research project 95408157.

References

1. Sarabian, C., et al. "Disgust in animals and the application of disease avoidance to wildlife management and conservation." Anim. Ecol.(2023).
2. Mitoh, S., et al. "Extreme Autotomy and Whole-Body Regeneration in Photosynthetic Sea Slugs." Biol. (2021).
3. Saleem, M., et al. "Review on Synthesis of Ferrocene-Based Redox Polymers and Derivatives and Their Application in Glucose Sensing." (2015).
4. Ali, A. M., et al. Ferrocene Functionalized Multi-Walled Carbon Nanotubes as Supercapacitor Electrodes. " J. Mol. Liq. (2020).

This study analyzes the natural vibration characteristics of grid beetle elytron plates (GBEPs), a type of laminated plate inspired by the sandwich structure of beetle forewings, under different angles of rotations.

Introduction: Inspired by the forewing structure of Trypoxylus dichotomus, GBEPs have been developed, exhibiting superior mechanical properties over traditional grid plates. This research investigates the effect of layer rotation on the natural vibrational frequencies of GBEPs, a crucial consideration for engineering applications.

Methods: The study utilizes COMSOL Multiphysics 6.1 and the ARPACK solver to analyze the vibrational response of GBEPs. Two identical plates were layered and rotated at angles from 0 to 45 degrees, in 9-degree increments, to examine changes in the first 9 natural frequency modes under various rotational configurations.

Results: Rotational adjustments significantly enhanced the clarity of vibrational modes, with dual-layered GBEPs showing more defined first 9 natural vibration modes compared to non-rotated structures. Rotation induced up to a 12.87% shift in natural frequencies, demonstrating the efficacy of this method in modulating vibrational characteristics.

Conclusion: This investigation highlights the capacity of simple structural modifications in biomimetic designs to achieve desired vibrational performances. Adjusting the orientation of layers in GBEPs allows for flexible vibrational properties, paving the way for their versatile application in different engineering contexts. The study leverages biomimetic principles to offer a novel approach for precise vibrational tuning in material design.

This study investigates the flexural mechanical properties of aluminum middle-trabecular beetle elytron plates (MBEP_N) with a significant height-to-thickness ratio core to understand how varying numbers of trabeculae (N) influence their bending resistance.

Introduction: Inspired by the natural world's engineering marvels, this study delves into the biomimetics of materials and structures, focusing on the remarkable structural mimicry of beetle elytron plates. Beetles, among Earth's most ancient organisms, have evolved lightweight yet robust elytra that conceal secrets of structural efficiency and durability. Mimicking the beetle elytron, we explore its analogous sandwich structure, akin to man-made aircraft wings, and its core's unique configuration—a honeycomb network reinforced with strategically placed trabeculae. This bio-inspired approach not only pays homage to the beetle's evolutionary refinement but also seeks to harness these natural designs for advanced engineering applications, embodying the essence of biomimetics in materials and structures.

Methods: This study employed a two-fold approach: quasi-static three-point bending tests on traditional honeycomb plates (MBEP₀) and bio-inspired MBEP₂ plates, followed by finite element analysis for MBEP variants (N = 2, 4, 6).

Results: MBEP₂ exhibited a notable 41.4% increase in flexural strength over traditional honeycomb plates. Contrary to expectations, higher N did not correspond to improved bending performance; instead, MBEP₂ outperformed others, including MBEP₆, with a distinct upward plateau on the load-displacement curve. Weak bending resistance was particularly noted near the upper plate of the first honeycomb wall across configurations, with deformation patterns varying with N. These findings suggest a complex relationship between trabeculae quantity and flexural performance, challenging simple linear assumptions.

Conclusions: This research uncovers previously unknown aspects of MBEP's flexural performance, highlighting its potential for engineering applications. The variation in trabeculae numbers and distributions offers insights into optimizing the material's mechanical properties for broader utilization in design and manufacturing.