Bio-inspired Devices Research Articles

Synaptic plasticity and learning behavior in transparent tungsten oxide-based memristors

In this study, by introducing reflex process into the precursor preparation and inkjet printing for high-quality top electrode deposition, we produced a solution-processed tungsten oxide based memristor, which not only overcomes the technical challenges in previous reports but also leads to an important step toward the development of high-performance memristor at low cost and ambient pressure. Various characteristics of synaptic plasticity and learning behaviors have been effectively demonstrated in the stacked device of Ag/WO3/FTO including short-term plasticity (STP) and long-term plasticity (LTP). A detailed investigation of short-term plasticity to long-term plasticity transition was given by changing the pulse number and strength. The memristive behavior in this work can be attributed to the formation/dissolution of Ag percolation paths between two electrodes. With regard to these promising features, the developed memristor may have great potential applications for bio-inspired neuromorphic devices.

Biomimetic Sonar for Electrical Activation of the Auditory Pathway

Relying on the mechanism of bat’s echolocation system, a bioinspired electronic device has been developed to investigate the cortical activity of mammals in response to auditory sensorial stimuli. By means of implanted electrodes, acoustical information about the external environment generated by a biomimetic system and converted in electrical signals was delivered to anatomically selected structures of the auditory pathway. Electrocorticographic recordings showed that cerebral activity response is highly dependent on the information carried out by ultrasounds and is frequency-locked with the signal repetition rate. Frequency analysis reveals that delta and beta rhythm content increases, suggesting that sensorial information is successfully transferred and integrated. In addition, principal component analysis highlights how all the stimuli generate patterns of neural activity which can be clearly classified. The results show that brain response is modulated by echo signal features suggesting that spatial information sent by biomimetic sonar is efficiently interpreted and encoded by the auditory system. Consequently, these results give new perspective in artificial environmental perception, which could be used for developing new techniques useful in treating pathological conditions or influencing our perception of the surroundings.

Electro-kinetically driven peristaltic transport of viscoelastic physiological fluids through a finite length capillary: Mathematical modeling

Analytical solutions are developed for the electro-kinetic flow of a viscoelastic biological liquid in a finite length cylindrical capillary geometry under peristaltic waves. The Jefferys’ non-Newtonian constitutive model is employed to characterize rheological properties of the fluid. The unsteady conservation equations for mass and momentum with electro-kinetic and Darcian porous medium drag force terms are reduced to a system of steady linearized conservation equations in an axisymmetric coordinate system. The long wavelength, creeping (low Reynolds number) and Debye–Hückel linearization approximations are utilized. The resulting boundary value problem is shown to be controlled by a number of parameters including the electro-osmotic parameter, Helmholtz–Smoluchowski velocity (maximum electro-osmotic velocity), and Jefferys’ first parameter (ratio of relaxation and retardation time), wave amplitude. The influence of these parameters and also time on axial velocity, pressure difference, maximum volumetric flow rate and streamline distributions (for elucidating trapping phenomena) is visualized graphically and interpreted in detail. Pressure difference magnitudes are enhanced consistently with both increasing electro-osmotic parameter and Helmholtz–Smoluchowski velocity, whereas they are only elevated with increasing Jefferys’ first parameter for positive volumetric flow rates. Maximum time averaged flow rate is enhanced with increasing electro-osmotic parameter, Helmholtz–Smoluchowski velocity and Jefferys’ first parameter. Axial flow is accelerated in the core (plug) region of the conduit with greater values of electro-osmotic parameter and Helmholtz–Smoluchowski velocity whereas it is significantly decelerated with increasing Jefferys’ first parameter. The simulations find applications in electro-osmotic (EO) transport processes in capillary physiology and also bio-inspired EO pump devices in chemical and aerospace engineering.

An analytical hierarchical model explaining the robustness and flaw-tolerance of the interlocking barb-barbule structure of bird feathers

Feathers can fulfill their aerodynamic function only if the pennaceous vane forms an airfoil stabilized by robust interlocking between barbules. Thus, revealing the robustness of the interlocking mechanical behavior of the barbules is very important to understand the function and long-term resilience of bird feathers. This paper, basing on the small- and large-beam deflection solutions, presents a hierarchical mechanical model for deriving the critical delamination conditions of the interlocking barbules between two adjacent barbs in bird feathers. The results indicate a high robustness and flaw-tolerant design of the structure. This work contributes to the understanding of the mechanical behavior of the robust interlocking barb-barbule structure of the bird feather, and provides a basis for design of feather-inspired materials with robust interlocking mechanism, such as advanced bio-inspired micro-zipping devices.

Influence of Nonsulfated Polysaccharides on the Properties of Electrospun Poly(lactic-co-glycolic acid) Fibers.

Biomimetic tissue engineering aspires to develop bioinspired implantable devices that would positively interact with the host. Given that glycosaminoglycans are involved in many physiological processes, whereas their deprivation is associated with pathophysiologies, functionalization of implantable devices with natural and/or synthetic carbohydrate moieties is at the forefront of scientific research and industrial innovation. Herein, we venture to assess the influence of various concentrations (0.01%, 0.1%, 1%) of hyaluronic acid and Ficoll on the structural, thermal, biomechanical and biological (human osteoblasts) properties of electrospun poly(lactic-co-glycolic acid) fibers. The addition of hyaluronic acid and Ficoll reduced the fiber diameter, with the 1% hyaluronic acid exhibiting the smallest fibers diameter (p < 0.001). Neither the addition of hyaluronic acid nor the addition Ficoll significantly affected the onset and peak temperatures (p > 0.05). All hyaluronic acid and Ficoll treatments significantly reduced stress at break, strain at break and elastic modulus values (p < 0.001). Hyaluronic acid and Ficoll did not affect osteoblast viability and metabolic activity temperatures (p > 0.05); the 1% hyaluronic acid and Ficoll significantly increased (p < 0.001) osteoblast proliferation at day 21. By day 21, the 1% hyaluronic acid and 1% Ficoll fibers showed the highest alkaline phosphatase activity and calcium deposition. At day 21, osteocalcin was not detected, whereas osteopontin was detected on all samples. Collectively, our data clearly illustrate the biological benefit of nonsulfated polysaccharides as functionalization molecules.

A device mimicking the biomechanical characteristics of crocodile skull for lumbar fracture reduction

Open surgery is currently the main treatment method for the lumbar burst fracture with neurological deficit but may irreversibly disrupt the lumbar anatomy. The minimally invasive surgery (MIS) techniques have recently gained increasing attention. However, their use is still limited to lumbar burst fractures mainly due to their difficulties in burst fracture reduction and decompression. Here we present a novel bio-inspired MIS device which can be used with an endoscope to reset the bone fragments retropulsed into the spinal canal within the wounded vertebral body. Its head jaw mimics the biomechanical characteristics of a crocodile rostrum to improve the performance in gripping and moving bone pieces in the confined space of a vertebral body. This study may be capable of converting the posterior open surgeries to the MIS procedures, and expands the use of the MIS techniques in the treatment of lumbar burst fractures.

Prospects for Photobiological Hydrogen as a Renewable Energy

BACKGROUND: Hydrogen is a clean, versatile fuel and energy carrier which can be produced by a range of renewable technologies for combustion, use in fuel cells, or as a manufacturing feedstock. Despite its attraction and significant technological innovation, commercial feasibility of photobiological hydrogen processes is far from demonstrated.OBJECTIVE: This review examines direct photobiological biohydrogen systems, with a particular focus on the main obstacles that must be overcome to deliver commercially viable, net energy positive systems. As part of this process the interactions between future photobiological biohydrogen systems and other parts of a renewable energy economy are examined to analyse potential technology integration paths.RESULTS: The primary driver for renewably produced hydrogen is the potential for CO2 emissions reductions. Renewable hydrogen is largely solar driven, either directly (e.g. natural photosynthesis, or bio-inspired devices) or indirectly (e.g. fermentation, electrical hydrolysis). A significant market for hydrogen already exists and is supported by extensive infrastructure providing significant opportunities for emerging renewable hydrogen streams. Several key physiological obstacles to efficient photobiohydrogen production have already been overcome, with oxygen tolerance as the most significant remaining problem.CONCLUSIONS: A much deeper understanding of photosynthetic biology is required before existing knowledge can be integrated with real world systems. Cross-fertilisation between engineering and biology represents the best path forward for implementation as a robust biotechnology.

(Invited) Oxide Neuron Transistor for High-Performance Biochemical Sensors

Synergic integration of presynaptic inputs from the dendrites plays an important role for sensory information process and cognitive computation, and the idea of building bio-inspired solid-state devices has been around for decades. In 1992, Shibata et al proposed the Si-based neuron transistors with multiple input gates that are capacitively coupled to a floating gate . The “on” or “off” state of the neuron transistors depends on the integrated effect of the multiple input gates. One of the unique features of the neuron transistors is the ultralow power dissipation during the calculation due to the gate-level sum operation in a voltage mode. From then on, Si-based neuron transistors have attracted much attention for chemical and biological detection due to the easy adjustment of threshold voltage. But, up to now, electrolyte-gated neuron transistors with amorphous oxide channel layers for biochemical sensing applications are not reported. For portable applications, low-voltage operation is preferred. Electrolyte gated electric-double-layer (EDL) transistors can act as potential candidates with a low operation voltage due to the strong EDL modulation at the electrolyte/channel interface. Recently, oxide-based EDL transistors gated by solid-state inorganic electrolytes were proposed by our group. At the same time, artificial synapses and neuron transistors with low power consumption and fundamental biological functions were mimicked in individual device. The sensitivity of a standard ion-sensitive field-effect transistor is limited to be 59.2 mV/pH (Nernst limit) at room temperature. Here, inspired by the dendritic integration and spiking operation of a biological neuron, oxide-based neuron transistors with multiple input gates are fabricated on flexible plastic substrates for pH sensor applications. When the neuron transistor sensor is operated in a quasi-static dual-gate synergic sensing mode, it shows a high pH sensitivity of ~105 mV/pH, which is higher than the Nernst limit. Our results also demonstrate that single-spike dynamic mode can remarkably improve pH sensitivity and reduce response/recover time and power consumption. At last, we find that appropriate depression applied on the sensing gate electrode can further enhance the pH sensitivity and reduce the power consumption. Our flexible neuron transistors provide a new-concept sensory platform for biochemical detection with high sensitivity, rapid response and ultralow power consumption.

A bio-inspired device for drag reduction on a three-dimensional model vehicle

In this paper, we introduce a bio-mimetic device for the reduction of the drag force on a three-dimensional model vehicle, the Ahmed body (Ahmed et al 1984 SAE Technical Paper 840300). The device, called automatic moving deflector (AMD), is designed inspired by the movement of secondary feathers on bird’s wing suction surface: i.e., secondary feathers pop up when massive separation occurs on bird’s wing suction surface at high angles of attack, which increases the lift force at landing. The AMD is applied to the rear slanted surface of the Ahmed body to control the flow separation there. The angle of the slanted surface considered is 25° at which the drag coefficient on the Ahmed body is highest. The wind tunnel experiment is conducted at ReH = 1.0 × 105–3.8 × 105, based on the height of the Ahmed body (H) and the free-stream velocity (U∞). Several AMDs of different sizes and materials are tested by measuring the drag force on the Ahmed body, and showed drag reductions up to 19%. The velocity and surface-pressure measurements show that AMD starts to pop up when the pressure in the thin gap between the slanted surface and AMD is much larger than that on the upper surface of AMD. We also derive an empirical formula that predicts the critical free-stream velocity at which AMD starts to operate. Finally, it is shown that the drag reduction by AMD is mainly attributed to a pressure recovery on the slanted surface by delaying the flow separation and suppressing the strength of the longitudinal vortices emanating from the lateral edges of the slanted surface.

Magnetic Control of the Light Reflection Anisotropy in a Biogenic Guanine Microcrystal Platelet.

Bioinspired but static optical devices such as lenses, retarders, and reflectors have had a significant impact on the designs of many man-made optical technologies. However, while numerous adaptive and flexible optical mechanisms are found throughout the animal kingdom, highly desirable biomimetic copies of these remarkable smart systems remain, in many cases, a distant dream. Many aquatic animals have evolved highly efficient reflectors based on multilayer stacks of the crystallized nucleic acid base guanine. With exceptional levels of spectral and intensity control, these reflectors represent an interesting design pathway towards controllable micromirror structures. Here we show that individual guanine crystals, with dimensions of 5 μm × 20 μm × 70 nm, can be magnetically controlled to act as individual micromirrors. By applying magnetic fields of 500 mT, the reflectivity of these crystals can be switched off and on for the change in reflectivity. Overall, the use of guanine represents a novel design scheme for a highly efficient and controllable synthetic organic micromirror array.

Bio-inspired device: a novel smart MR spring featuring tendril structure

Smart materials such as piezoelectric patches, shape memory alloy, electro and magneto rheological fluid, magnetostrictive materials, etc are involved by far to design intelligent and high performance smart devices like injectors, dental braces, dampers, actuators and sensors. In this paper, an interesting smart device is proposed by inspiring on the structure of the bio climber plant. The key enabling concept of this proposed work is to design the smart spring damper as a helical shaped tendril structure using magneto-rheological (MR) fluid. The proposed smart spring consists of a hollow helical structure filled with MR fluid. The viscosity of the MR fluid decides the damping force of helical shaped smart spring, while the fluid intensity in the vine decides the strength of the tendril in the climber plant. Thus, the proposed smart spring can provide a new concept design of the damper which can be applicable to various damping system industries with tuneable damping force. The proposed smart spring damper has several advantageous such as cost effective, easy implementation compared with the conventional damper. In addition, the proposed spring damper can be easily designed to adapt different damping force levels without any alteration.

Optical vortex induction via light–matter interaction in liquid-crystal media

Optical vortices are attracting much attention because of their applications in various fields of optical processing, communications, enhanced imaging systems, and bio-inspired devices. Different methods to generate optical vortices have been devised to date. Among them, several are based on the exploitation of light–matter interaction in liquid-crystal media. This review focuses on the main mechanisms of vortex generation in liquid crystals, in particular on vortex generation induced by umbilics, that is, defects arising in homeotropically aligned nematic cells, which act as topological matter templates able to realize the conversion from spin to orbital angular momentum of an incoming Gaussian beam. Optical vortex induction in a photosensitive light valve is presented as a self-stabilizing mechanism leading to reconfigurable and programmable vortex arrays. On each lattice site, every matter vortex acts as a photonic spin-to-orbital momentum coupler, converting input arrays of circularly polarized beams into output arrays of vortex beams with topological charges consistent with the matter lattice symmetry.

Multi-Stacked Supported Lipid Bilayer Micropatterning through Polymer Stencil Lift-Off.

Complex multi-lamellar structures play a critical role in biological systems, where they are present as lamellar bodies, and as part of biological assemblies that control energy transduction processes. Multi-lamellar lipid layers not only provide interesting systems for fundamental research on membrane structure and bilayer-associated polypeptides, but can also serve as components in bioinspired materials or devices. Although the ability to pattern stacked lipid bilayers at the micron scale is of importance for these purposes, limited work has been done in developing such patterning techniques. Here, we present a simple and direct approach to pattern stacked supported lipid bilayers (SLBs) using polymer stencil lift-off and the electrostatic interactions between cationic and anionic lipids. Both homogeneous and phase-segregated stacked SLB patterns were produced, demonstrating that the stacked lipid bilayers retain lateral diffusivity. We demonstrate patterned SLB stacks of up to four bilayers, where fluorescence resonance energy transfer (FRET) and quenching was used to probe the interactions between lipid bilayers. Furthermore, the study of lipid phase behaviour showed that gel phase domains align between adjacent layers. The proposed stacked SLB pattern platform provides a robust model for studying lipid behaviour with a controlled number of bilayers, and an attractive means towards building functional bioinspired materials or devices.

Android and PSoC Technology Applied to Electronic Tongue Development

Nowadays, in the food industry, analyzing the quality of alimentary products has become a necessity. As a result, producers have been searching for new accurate methods to analyze food quality. The development of bio-inspired devices (electronic nose and electronic tongue) is a potential alternative to supply this need. The current project shows the development of a prototype circuit based on PSoC technology, which is used as a signal processing stage in an electronic tongue device with the ability to discriminate and classify samples of raw milk. In general, electronic tongues consist of electrochemical sensors array, a signals processing stage and a data processing stage. PSoC is an integrated circuit composed of analog and digital blocks into a configurable core. With the use of PSoC microchip, it is possible to develop a portable and small electrochemical device. This prototype takes measures from electrochemical sensors exposed to samples of drinks using the cyclic voltammetry technique; these signals are processed and transmitted to the next stage, which shows the response from the electrochemical sensors through an I-V curve, called voltammogram. With the development of this device, it was found that the application of PSoC technology on electrochemical measurement devices is important, due to its ability to develop cheaper, smaller, faster and sturdier devices.

Inverse Kinematic Analysis of Three Link Mechanism for Fin Actuation of Fish Like Micro Device

In this paper, inverse kinematic analysis of a proposed three link mechanism of a bio-inspired micro scanning device towed underwater by a surface vessel to actuate its aileron fins for its depth control and for its stabilization against roll is performed. Mechanism is actuated by IPMC actuators. To speed up the design verification process, computer aided simulations are used to perform motion analysis of the proposed IPMC actuated mechanism through Pro/Mechanism tool. Inverse kinematic analysis is performed to find out the joint variables of the mechanism to realize fin actuation along desired path. Displacements, velocities and accelerations of the links constructing mechanism are found out to establish their interrelationship. Results are analysed for the study of mechanism efficacy and for sizing the IPMC actuators. This paper contributes to introduce a new approach of virtual prototyping using advanced simulation tools for analysis and design verification of IPMC actuated mechanisms for biomimetic applications before moving into functional prototype stage.

Strain tunable optics of elastomeric microlens array

Microlens arrays (MLAs) have attracted great attention with their important applications in many fields, such as optical communications, organic light emitting diodes (OLEDs), thin film photovoltaic cells, and novel bio-inspired devices. The dynamically tunable MLAs whose optical properties can be changed in a controllable manner are especially desirable in some recent developments. In this study, a very simple tuning method via mechanical stretching is proposed to tune the optics of elastomeric MLAs. Theoretical mechanics and optics studies are combined to demonstrate the tunability of elastomeric MLAs under both uniaxial and equibiaxial stretching. The results show that extremely large tuning range of the focal length can be achieved using this method. This theoretical study can provide important implications to not only the design of tunable MLAs, but also developments that require controllable optical elements.

Biologically inspired band-edge laser action from semiconductor with dipole-forbidden band-gap transition

A new approach is proposed to light up band-edge stimulated emission arising from a semiconductor with dipole-forbidden band-gap transition. To illustrate our working principle, here we demonstrate the feasibility on the composite of SnO2 nanowires (NWs) and chicken albumen. SnO2 NWs, which merely emit visible defect emission, are observed to generate a strong ultraviolet fluorescence centered at 387 nm assisted by chicken albumen at room temperature. In addition, a stunning laser action is further discovered in the albumen/SnO2 NWs composite system. The underlying mechanism is interpreted in terms of the fluorescence resonance energy transfer (FRET) from the chicken albumen protein to SnO2 NWs. More importantly, the giant oscillator strength of shallow defect states, which is served orders of magnitude larger than that of the free exciton, plays a decisive role. Our approach therefore shows that bio-materials exhibit a great potential in applications for novel light emitters, which may open up a new avenue for the development of bio-inspired optoelectronic devices.

Bio-inspired Microfluidic Devices for Passive, Directional Liquid Transport: Model-based Adaption for Different Materials

The Texas Horned lizard has the ability to harvest moisture from ambience with its skin and to transport water directionally to its snout; at the same time water is hindered to flow in opposite direction. We present a passive microfluidic device for directional liquid transport which is inspired by this natural role model. To this end, we deduce a subnatural capillary network from the measurement data of the Texas Horned lizard's skin. We adapt the network to various liquid-polymer combinations with the help of a mathematical model. Applying a CO2 laser we engrave the structures into poly(methyl methacrylate) (PMMA). By distance measurements we verify that our devices transport liquids of different contact angles in a preferential direction, while stopping it in opposite direction. The applied network of interconnected capillary channels is advantageous, when it comes to defects during production or when particles block part of the capillary channels. The proposed concept is thought to be useful for micro-analysis devices and lubrication.

Swimming and crawling motility at microscopic scales: from biological templates to bio-inspired devices

We discuss the mechanical bases of cellular motility by swimming and crawling. Special emphasis is placed on the connections between low Reynolds number swimming and Geometric Control Theory, and on the geometric structure of the underlying equations of motion. We examine some concrete examples, taken from the case studies that have been recently considered by our group. These include reverse engineering of the euglenoid movement, self-propelled droplets of active fluids, and one-dimensional models of slender crawlers.

A bio-inspired memory device based on interfacing Physarum polycephalum with an organic semiconductor

The development of devices able to detect and record ion fluxes is a crucial point in order to understand the mechanisms that regulate communication and life of organisms. Here, we take advantage of the combined electronic and ionic conduction properties of a conducting polymer to develop a hybrid organic/living device with a three-terminal configuration, using the Physarum polycephalum Cell (PPC) slime mould as a living bio-electrolyte. An over-oxidation process induces a conductivity switch in the polymer, due to the ionic flux taking place at the PPC/polymer interface. This behaviour endows a current-depending memory effect to the device.