Multifunctional flexible optical waveguide sensor: on the bioinspiration for ultrasensitive sensors development

This paper presents the development of a bioinspired multifunctional flexible optical sensor(BioMFOS)as an ultrasensitive tool for force(intensity and location)and orientation sensing.The sensor structure is bioinspired in orb webs,which are multifunctional devices for prey capturing and vibration transmission.The multifunctional feature of the structure is achieved by using transparent resins that present both mechanical and optical properties for structural integrity and strain/deflection transmission as well as the optical signal transmission properties with core/cladding configuration of a waveguide.In this case,photocurable and polydimethylsiloxane(PDMS)resins are used for the core and cladding,respectively.The optical transmission,tensile tests,and dynamic mechanical analysis are performed in the resins and show the possibility of light transmission at the visible wavelength range in conjunction with high flexibility and a dynamic range up to 150 Hz,suitable for wearable applications.The BioMFOS has small dimensions(around 2 cm)and lightweight(0.8 g),making it suitable for wearable application and clothing integration.Characterization tests are performed in the structure by means of applying forces at different locations of the structure.The results show an ultra-high sensitivity and resolution,where forces in theμN range can be detected and the location of the applied force can also be detected with a sub-millimeter spatial resolution.Then,the BioMFOS is tested on the orientation detection in 3D plane,where a correlation coefficient higher than 0.9 is obtained when compared with a gold-standard inertial measurement unit(IMU).Furthermore,the device also shows its capabilities on the movement analysis and classification in two protocols:finger position detection(with the BioMFOS positioned on the top of the hand)and trunk orientation assessment(with the sensor integrated on the clothing).In both cases,the sensor is able of classifying the movement,especially when analyzed in conjunction with preprocessing and clustering techniques.As another wearable application,the respiratory rate is successfully estimated with the BioMFOS integrated into the clothing.Thus,the proposed multifunctional device opens new avenues for novel bioinspired photonic devices and can be used in many applications of biomedical,biomechanics,and micro/nanotechnology.

Mechanical properties of crosslinks controls failure mechanism of hierarchical intermediate filament networks

Intermediate filaments are one of the key components of the cytoskeleton in eukaryotic cells, and their mechanical properties are found to be equally important for physiological function and disease. While the mechanical properties of single full length filaments have been studied, how the mechanical properties of crosslinks affect the mechanical property of the intermediate filament network is not well understood. This paper applies a mesoscopic model of the intermediate network with varied crosslink strengths to investigate its failure mechanism under the extreme mechanical loading. It finds that relatively weaker crosslinks lead to a more flaw tolerant intermediate filament network that is also 23% stronger than the one with strong crosslinks. These findings suggest that the mechanical properties of interfacial components are critical for bioinspired designs which provide intriguing mechanical properties.

Bioinspired tungsten-copper composites with Bouligand-type architectures mimicking fish scales

The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in metals.Here bioinspired tungsten-copper composites with different Bouligand-type architectures mimicking fish scales were fabricated by infiltrating a copper melt into woven contextures of tungsten fibers.These composites exhibit a synergetic enhancement in both strength and ductility at room temperature along with an improved resistance to high-temperature oxidization.The strengths were interpreted by adapting the classical laminate theory to incorporate the characteristics of Bouligand-type architectures.In particular,under load the tungsten fibers can reorient adaptively within the copper matrix by their straightening,stretching,interfacial sliding with the matrix,and the cooperative kinking deformation of fiber grids,representing a successful implementation of the optimizing mechanisms of the Bouligand-type architectures to enhance strength and toughness.This study may serve to promote the development of new high-performance tungsten-copper composites for applications,e.g.,as electrical contacts or heat sinks,and offer a viable approach for constructing bioinspired architectures in metallic materials.

Design,hydrodynamic analysis,and testing of a bioinspired controllable wing mechanism with multi-locomotion modes for hybrid-driven underwater gliders

Hybrid-driven technology,which can improve the sailing performance of underwater gliders(UGs),has been successfully used in ocean observation.However,a hybrid-driven UG(HUG)with an added tail propeller is still unable to achieve backward and turning motion with a body length radius,and the hydrodynamic pitch moment acting on the HUG that is mainly caused by the fixed-wing makes it difficult to achieve high-precision attitude control during fixed-depth navigation.To solve this problem,a two-degree-of-freedom bioinspired controllable wing mechanism(CWM)is proposed to improve the maneuverability and cruising ability of HUGs.The CWM can realize five motion modes:modifying the dihedral angle or anhedral angle,changing the frontal area of the wing,switching the wing from horizontal to be a vertical rudder,flapping the wing as propulsion,and rotating the wing as a vector propeller.First,the design process of the CWM is provided,and hydrodynamic forces in each motion mode of three CWMs with different trailing edge sweepback angles(TESA)and attitude angles are analyzed through computational fluid dynamics simulation.The relationship between hydrodynamics and the attitude angles or TESA of the CWM is analyzed.Then,experiments are conducted to measure the hydrodynamics of the CWM when it is in a flapping wing mode and rotating the wing as a vector propeller,respectively.The hydrodynamic forces obtained from the simulation are consistent with data measured by a force sensor,proving the credibility of the simulated hydrodynamics.Subsequently,by applying the results of the hydrodynamic force in this study,the flapping trajectory of the wingtip is planned using the cubic spline interpolation method.Furthermore,two underwater demo vehicles with a pair of CWMs are developed,and experiments are conducted in a water tank,further validating and demonstrating the feasibility of the proposed CWM.

Analysis of Bio-inspired Fishbone Based Corrugated Rib for Adaptive Camber Morphing

Bioinspired active camber morphing is an innovative solution for the aerodynamic performance enhancement of flight vehicles such as Micro Aerial Vehicles(MAVs)and Unmanned Aerial Vehicles(UAVs).In the present article,a bio-inspired Fish Bone Active Camber(FishBAC)corrugated rib design concept with and without a spine for an Unmanned Aerial Vehicle(UAV)is proposed.The wing model is composed of multiple corrugated ribs and a splitted spar for connecting each rib.The rib geometry is subjected to static structural analysis using ANSYS Finite Element Analysis(FEA)module under the unit load conditions.The deformation modes are first extracted from the solution of the wind tunnel test and the elastically deformed NACA 4412 profile will be used to perform Fluid-Structure Interaction(FSI)studies as a partly coupled analysis.FishBAC corrugated rib with spine design is a stable structure as inspired from nature species that can withstand elastic and inertial loads.Computational fluid dynamics(CFD)simulation is performed to compute the coefficient of lift(Cl),coefficient of drag(Cd)at different Angle of Attack(AoA)for a modified NACA 4412 airfoil and the pressure loads acting on the deformed shape is extracted.The Cl obtained for the modified airfoil at lower AoA is about 60–80%higher and the maximum Cl(Clmax)is 62%higher than the baseline airfoil.The Cd of modified airfoil is reduced about 20%at the AoAα=3°as compared with the baseline model.The proposed corrugated rib structure has been successfully 3D printed with Polylactic Acid plus(PLA+)material and the wind tunnel testing is done to validate the Cl,Cd values obtained through CFD simulations and the results are presented.

Performance enhancement of futuristic airplanes by nature inspired biomimetic fish scale arrays--A design approach

Biomimetics has an immense potential to drive the next generation of technologies forward by propounding competent solutions from nature.For decades,the nonsmooth topography of most living creatures has been critical to their existence and survival.Contrary to human-made smooth surfaces,when adapted for fluid flow applications,nonsmooth surfaces can enhance the overall aerodynamic performance by reducing the drag force.Recently,the bioinspired scale structure of fish has been identified as a key biomimetic derivative for improving the aerodynamic efficiency in various cross-domain applications.This study investigates the aerodynamics of a fish scale array(FSA)NACA 0021 model at a specific Reynolds number(Re)of approximately 2.46×105 that is meant for laminar flow conditions using Computational Fluid Dynamics(CFD)tools and a subsonic wind tunnel facility.A 3D printed biomimetic FSA film is developed and affixed on the NACA 0021 wing profile for the experimental investigation,followed by flow visualization through the smoke tunnel facility.As proved qualitatively under specific aerodynamic conditions,the creation of velocity streaks has a major role in the drag reduction process.To obtain a clear perspective of flow across the overlapping fish scale structures,the results are focused on the central and overlapping regions of the FSA structure.The experiment has proved the existence of a combined formation of low and high velocity streaks in central and overlapping regions.The FSA 0021 model showed a maximum drag reduction of 9.57%,which was attributed to the streak formation phenomenon observed in the overlapping FSA configuration.