Polystyrene Petri dishes are in use in hundreds of thousands of laboratories world wide. Cell culture experiments performed in them provide fundamental information in a wide range of applications, including but not limited to testing novel biomaterials and pharmaceuticals, and stem cell research. These experiments cost billions of dollars per year. In this study we report on a potential deficiency of polystyrene Petri dishes, possibly caused by an increase in interfacial pH under relevant culture conditions and affecting cell performance. We conclude that cell performance on Petri dishes could be improved by improving the Petri dishes. As a spin-off of our study we postulate the concept that cancer cells and stem cells are social. It is impossible to validate this concept on the basis of the model established in this paper. However, the coherence of our insights may encourage further study and lead to the development of a qualitative improvement of cell culture devices, including Petri dishes and culture flasks, to the identification of potential strategies for chemotherapy and chemoprevention that could suppress progression of metastasis, and to the establishment of improved settings for tissue engineering and stem cell research. An immediate recommendation of our study is to use chemically and biologically inert substrates for important cell culture experiments, for example, nanocrystalline diamond.

Macro-/Micro-structures and mechanical properties of the elytra of beetles were studied. The Scan Electron Microscope (SEM) and optical microscopy were employed to observe the macro-/micro-structure of the surface texture and cross-section structure of elytra. Nano-indentation was carried out to measure the elastic modulus and the hardness of elytra. Tensile strengths of elytra in lateral and longitudinal directions were measured by a multifunctional testing machine. The coupling force between elytra was also measured and the clocking mechanism was studied. SEM images show the similar geometric structure in transverse and longitudinal sections and multilayer – dense epicuticle and exocuticle, followed by bridge piers with a helix structured fibers, which connect the exocuticle to the endodermis, and form an ellipse empty to reduce the structure weight. The elastic modulus and the hardness are topologically distributed and the mechanical parameters of fresh elytra are much higher than those of dried elytra. The tensile strength of the fresh biological material is twice that of dried samples, but there is no clear difference between the data in lateral and longitudinal directions. Coupling forces measured are 6.5 to 160 times of beetles’ bodyweight, which makes the scutellum very important in controlling the open and close of the elytra. The results provide a biological template to inspire lightweight structure design for aerospace engineering.

The surface properties of earthworms were studied using nitrogen adsorption/desorption isotherm and dynamic contact angle measurement with the aim to understand their non-stain behaviour. The results obtained by applying dynamic contact angle technique using water, glycerol, cooking oil and dimethylsilicone show that the surface properties of earthworms are a function of time. The critical surface energy, calculated using advancing angle, is as low as 11 ? 10−3 J•m−2. However this hydrophobic behaviour at the initial contact moment changes progressively into hydrophilic as time goes by. This behaviour together with the creeping movement of corrugated surface is believed to be responsible for the non-stain behaviour of earthworms. The nitrogen adsorption isotherm of dried skin of earthworms at 77.3 K exhibits more or less Type V isotherm with surface area of 13 m2•g−1 calculated using the ?s plot. The Type V isotherm is the indication of weak interaction between nitrogen and the worm surface.

Partially crosslinked and sulfonated poly(vinyl alcohol) (s-PVA) membranes were prepared as ion-conductive matrices of Ionic Polymer-Metal Composite (IPMC) and a new IPMC based on the s-PVA membrane was fabricated via an electroless plating procedure of platinum. PVA was reacted with sulfosuccinic acid (SSA) as a crosslinking agent with a sulfonic group and 4-(2-hydroxyethyl)piperazine-1-propanesulfonic acid (EPPS) as a side chain with a sulfonic group. The crosslinked s-PVA membranes were characterized using a FT-IR spectroscope and a scanning electron microscope-combined energy-dispersive X-ray spectrometer and were assessed in terms of water absorption, proton conductivity, and the feasibility of electroless plating. Among the prepared ionomers, the s-PVA membrane obtained at 20 wt.% SSA and 10 wt.% EPPS (S20E10 membrane) registered the highest proton conductivity of 2.9 ? 10−2 S•cm−1, which corresponds to one third of that of Nafion series, and only the S20E10 membrane was successfully plated via the electroless plating method without any crack and broken part. The s-PVA-based IPMC showed the one-directional displacement with 1-minute-long time-lapse comparable to typical Nafion-based IPMCs. However, the displacement under an AC potential was very limited due to its slow deformation response and the actuation performance was severely varied with actuation time including the short service life of several minutes in air. The short and variable actuation of the s-PVA-based IPMC was attributed to its large variation of surface and ionic resistances during air-operation, which is induced by the low ratio of bound to free water.

This paper describes a single-step method for the biomimetic synthesis of stably suspended magnetite nanoparticles in poly(vinyl alcohol) termed ferrofluids. The challenge is to synthesize water based stable magnetic colloids with a control over the particle size and morphology for biomedical applications. The polymer possibly plays a dual role of a surfactant and a functionalizing agent. Transmission electron microscopy, infrared spectroscopy and vibrating sample magnetometry were used to investigate the properties of the synthesized ferrofluids. It has a strong affinity towards the tryptophan residues in bovine serum albumin protein as determined from the fluorescence emission studies. For in vivo applications this could indirectly mean a resistance to immune response and thus ensure long–term circulation. The ability of the synthesized ferrofluid to bind a chemotherapeutic drug ceftriaxone and its ionic release was observed.  The polymer hydroxyl group allows drug-binding and the magnetic property allows targeting to specific sites. Magnetic hybrid fluids with combined advantages of magnetism and polymer open up new perspectives for applications.

This paper presents a novel approach to modelling carangiform fish-like swimming motion for multi-joint robotic fish so that they can obtain fish-like behaviours and mimic the body motion of carangiform fish. A given body motion function of fish swimming is firstly converted to a tail motion function which describes the tail motion relative to the head. Then, the tail motion function is discretized into a series of tail postures over time. Thirdly, a digital approximation method calculates the turning angles of joints in the tail to approximate each tail posture; and finally, these angles are grouped into a look-up table, or regressed to a time-dependent function, for practically controlling the tail motors in a multi-joint robotic fish. The paper made three contributions: tail motion relative to the head, an error function for digital approximation and regressing a look- up table for online optimization. To prove the feasibility of the proposed methodology, two basic swimming motion patterns, cruise straight and C-shape sharp turning, are modelled and implemented in our robotic fish. The experimental results show that the relative tail motion and the approximation error function are good choices and the proposed method is feasible.

A video tracking system for measuring three-dimensional kinematics of a free-swimming fish is presented. The tracking is accomplished by simultaneously taking images from the ventral view and the lateral view of the fish with two cameras mounted on two computer-controlled and mutually orthogonal translation stages. Compared to the previous system we reported, the time resolution is greatly improved. A koi carp is selected for the experiment. By processing the images caught by the video tracking system, the three-dimensional kinematics of the koi carp during a continuous swimming containing several moderate maneuvers are obtained. In particular, the pitching motion of fish body and the tail motion, including lateral excursion, variation in tail height and torsion, are revealed for burst-and-coast swimming and turning maneuver. The error analysis is also provided for the measurement results.

Vorticity control mechanisms for flapping foils play a guiding role in both biomimetic thrust research and modeling the forward locomotion of animals with wings, fins, or tails. In this paper, a thrust-producing flapping lunate tail is studied through force and power measurements in a water channel. Proper vorticity control methods for flapping tails are discussed based on the vorticity control parameters: the dimensionless transverse amplitude, Strouhal number, angle of attack, and phase angle. Field tests are conducted on a free-swimming biomimetic robotic fish that uses a flapping tail. The results show that active control of Strouhal number using fuzzy logic control methods can efficiently reduce power consumption of the robotic fish and high swimming speeds can be obtained. A maximum speed of 1.17 length specific speed is obtained experimentally under conditions of optimal vorticity control. The St of the flapping tail is controlled within the range of 0.4~0.5.

Undulation fishes, whose propulsion is mainly achieved by undulating ribbon fins, are good at maneuvering or stabilizing at low speeds. This paper suggests and proposes a two-dimensional approximate computational model, which is used to conduct an initial analysis on undulation propulsion scheme. It is believed that this undulating mode has a better potential for exploitation in artificial underwater systems. Hydrodynamics of two-dimensional undulating fins under a series of kinematical parameter sets is explored via numerical simulation. The periodicity of undulation forces and moments is studied. The effects of inlet velocity, wavelength, undulation frequency, and undulation amplitude are investigated. Furthermore, a dimensionless two-parameter model for undulation surge force is established with a given wavelength (in terms of, a single wavelength or a dual wavelength) using statistical method. The work in this paper is able to provide studies on bionic undulation mode. It has also formed a meaningful basis for three-dimensional (3D) hydrodynamics and corresponding control methods in bionic undulation robots.

In this work, we first present a method to experimentally capture the free flight of a beetle (Allomyrina dichotoma), which is not an active flyer. The beetle is suspended in the air by a hanger to induce the free flight. This flight is filmed using two high-speed cameras. The high speed images are then examined to obtain flapping angle, flapping frequency, and wing rotation of the hind wing. The acquired data of beetle free flight are used to design a motor-driven flapper that can approximately mimic the beetle in terms of size, flapping frequency and wing kinematics. The flapper can create a large flapping angle over 140? with a large passive wing rotation angle. Even though the flapping frequency of the flapper is not high enough compared to that of a real beetle due to the limited motor torque, the flapper could produce positive average vertical force. This work will provide important experience for future development of a beetle-mimicking Flapping-Wing Micro Air Vehicle (FWMAV).

Inspired by the fact that a high flexible wing in nature generates high aerodynamic performance, we investigated the aerodynamic performance of the flapping wing with different chord flexures. The unsteady, incompressible, and viscous flow over airfoil NACA0012 in a plunge motion was analyzed by using Navier-Stokes equation. Grid deformation, in which finite element and interpolation ideas are mixed, was introduced for computing large grid deformation caused by the chord flexures. We explored the optimal phase angle for thrust force and propulsive efficiency by varying the chord flexure from 0.05 to 0.7 when reduced frequency and plunge amplitude were fixed. Throughout parametric study on the phase angle and chord flexure amplitude, the maximum thrust force is achieved near at 0? in all given conditions, meanwhile, it is found that the optimal phase angle has dependency of chord flexure amplitude, which achieves higher aerodynamic performance compared to previous studies. These findings will provide a useful guideline for determining wing flexibility in design of a bio-mimetic air vehicle.

Using a sophisticated aerodynamic method, the effects of extremely large dihedral on the aerodynamic characteristics of birds are determined. With this method, it is possible to generate solutions for the addressed aerodynamic problem, which shows a high complexity due to interference effects caused by dihedral and pronounced 3-dimensional flow properties as well as due to complex wing geometries. From the obtained results it follows that extremely large dihedral has substantial effects on the aerodynamic force characteristics. There are significant changes in the lift, the drag and the side force, thus affecting the flight performance. Furthermore, the obtained results show that the aerodynamic rolling and yawing moment characteristics are influenced by extremely large dihedral to a high degree. This is a significant outcome for lateral-directional stability because the aerodynamic rolling and yawing moment characteristics have a determinative influence here.

This paper introduces a flight simulation of an ornithopter (flapping-wing air vehicle) based on the flexible multi-body dynamics, a refined flapping-wing aerodynamic model and the fluid-structure interaction approach. A simulated ornithopter was modeled using the multi-body dynamics software, MSC.ADAMS, where the flexible parts can be included by importing a finite element model built in the finite element analysis software, ANSYS. To model the complex aerodynamics of flapping-wing, an improved version of modified strip theory was chosen. The proposed integrative simulation framework of ornithopter was validated by the wind tunnel test data reported in the literature. A magpie-sized model ornithopter was numerically designed and simulated to have the longitudinal trim flight condition. We observed a limit-cycle-oscillation of flight state variables, such as pitch attitude, altitude, flight speed, during the trimmed flight of the model ornithopter. Under the trimmed condition of free flight of the model ornithopter, we fixed all the degrees of freedom at the center of gravity to measure the constraint forces and moment. The concept of the “zero moment point” is introduced to explain the physics of ornithopter trimmed longitudinal flight.