Evaluation of Food Fineness by the Bionic Tongue Distributed Mechanical Testing Device.

In this study, to obtain a texture perception that is closer to the human sense, we designed eight bionic tongue indenters based on the law of the physiology of mandibular movements and tongue movements features, set up a bionic tongue distributed mechanical testing device, performed in vitro simulations to obtain the distributed mechanical information over the tongue surface, and preliminarily constructed a food fineness perception evaluation model. By capturing a large number of tongue movements during chewing, we analyzed and simulated four representative tongue movement states including the tiled state, sunken state, raised state, and overturned state of the tongue. By analyzing curvature parameters and the Gauss curvature of the tongue surface, we selected the regional circle of interest. With that, eight bionic tongue indenters with different curvatures over the tongue surface were designed. Together with an arrayed film pressure sensor, we set up a bionic tongue distributed mechanical testing device, which was used to do contact pressure experiments on three kinds of cookies-WZ Cookie, ZL Cookie and JSL Cookie-with different fineness texture characteristics. Based on the distributed mechanical information perceived by the surface of the bionic tongue indenter, we established a food fineness perception evaluation model by defining three indicators, including gradient, stress change rate and areal density. The correlation between the sensory assessment and model result was analyzed. The results showed that the average values of correlation coefficients among the three kinds of food with the eight bionic tongue indenters reached 0.887, 0.865, and 0.870, respectively, that is, a significant correlation was achieved. The results illustrate that the food fineness perception evaluation model is effective, and the bionic tongue distributed mechanical testing device has a good practical significance for obtaining food texture mouthfeel information.

Flexible Capacitive Tactile Sensor Based on Micropatterned Dielectric Layer.

Flexible tactile sensors are considered as an effective way to realize the sense of touch, which can perform the synchronized interactions with surrounding environment. Here, the utilization of bionic microstructures on natural lotus leaves is demonstrated to design and fabricate new-type of high-performance flexible capacitive tactile sensors. Taking advantage of unique surface micropattern of lotus leave as the template for electrodes and using polystyrene microspheres as the dielectric layer, the proposed devices present stable and high sensing performance, such as high sensitivity (0.815 kPa-1 ), wide dynamic response range (from 0 to 50 N), and fast response time (≈38 ms). In addition, the flexible capacitive sensor is not only applicable to pressure (touch of a single hair), but also to bending and stretching forces. The results indicate that the proposed capacitive tactile sensor is a promising candidate for the future applications in electronic skins, wearable robotics, and biomedical devices.

Bionic intelligent soft actuators: high-strength gradient intelligent hydrogels with diverse controllable deformations and movements.

A series of novel nanofibrillated cellulose (NFC) reinforced gradient intelligent hydrogels with high response rate, multiple response patterns and diversified self-driven functions were successfully prepared. Based on the effect of the hydroxide radical of NFC on the addition reaction, and on the dehydration synthesis, the variation of NFC significantly regulated the gradient structure of the intelligent hydrogels. In addition to the infiltration property of graphene oxide (GO), reinforcement of NFC enhanced the crosslinking density and Young's modulus, which built a relationship between material characteristics and near infrared laser response rate. Intelligent hydrogel actuators realized bending deformation, curling deformation, switching movements and obstacle avoidance movements. The hydrogels with high Young's modulus exhibited relatively low self-driven rates and efficiency. The self-driven mechanisms of NFC reinforced gradient intelligent hydrogels were revealed effectively by constructing the mathematical relationship curvature variation, bending degree, deformation displacement, material characteristics and incentive intensity. The investigation showed a new path for the combination of mechanical property, intelligent property and functional property of intelligent hydrogels in a bionic soft robot and health engineering.

Rhinophore bio-inspired stretchable and programmable electrochemical sensor.

Rhinophore, a bio-chemical sensory organ with soft and stretchable/retractable features in many marine molluscs species, exhibits tunable chemosensory abilities in terms of far/near-field chemical detection and molecules' source orientation. However, existing artificial bio-chemical sensors cannot provide tunable modality sensing. Inspired by the anatomical units (folded sensory epithelium) and the functions of a rhinophore, this work introduces a stretchable electrochemical sensor that offers a programmable electro-catalytic performance towards glucose based on the fold/unfold regulation of the gold nanomembrane on an elastic fiber. Geometrical design rationale and covalent bonding strategy are used to realize the robust mechanical and electrical stability of this stretchable bionic sensor. Electrochemical tests demonstrated that the sensitivities of the as-prepared bionic sensor exhibit a linear relationship with its strain states from 0% to 150%. Bio-inspired sensory functions are tested by regulating the strain of the bionic sensor. The sensor achieves a sensitivity of 195.4 µA mM-1 in a low glucose concentration range of 8-206 µM at 150% strain for potentially far-field chemical detection, and a sensitivity of 14.2 µA mM-1 in a high concentration range of 10-100 mM at 0% strain for near-field chemical detection. Moreover, the bionic sensor performs the detection while extending its length can largely enhance the response signal, which is used to distinguish the molecules' source direction. This proposed bionic sensor can be useful in wearable devices, robotics and bionics applications which require diverse modality sensing and smart chemical tracking system.

Self-Healable Conductive Nanocellulose Nanocomposites for Biocompatible Electronic Skin Sensor Systems.

Electronic skins are developed for applications such as biomedical sensors, robotic prosthetics, and human-machine interactions, which raise the interest in composite materials that possess both flexibility and sensing properties. Polypyrrole-coated cellulose nanocrystals and cellulose nanofibers were prepared using iron(III) chloride (FeCl3) oxidant, which were used to reinforce polyvinyl alcohol (PVA). The combination of weak H-bonds and iron coordination bonds and the synergistic effect of these components yielded self-healing nanocomposite films with robust mechanical strength (409% increase compared to pure PVA and high toughness up to 407.1%) and excellent adhesion (9670 times greater than its own weight) to various substrates in air and water. When damaged, the nanocomposite films displayed good mechanical (72.0-76.3%) and conductive (54.9-91.2%) recovery after a healing time of 30 min. More importantly, the flexible nanocomposites possessed high strain sensitivity under subtle strains (<48.5%) with a gauge factor (GF) of 2.52, which was relatively larger than the GF of ionic hydrogel-based skin sensors. These nanocomposite films possessed superior sensing performance for real-time monitoring of large and subtle human motions (finger bending motions, swallowing, and wrist pulse); thus, they have great potentials in health monitoring, smart flexible skin sensors. and wearable electronic devices.

Short-Term Plasticity and Long-Term Potentiation in Artificial Biosynapses with Diffusive Dynamics.

The development of electronic devices possessing the functionality of biological synapses is a crucial step toward replicating the capabilities of the human brain. Of the various materials that have been used to realize artificial synapses, renewable natural materials have the advantages of being abundant, inexpensive, biodegradable, and ecologically benign. In this study, we report a biocompatible artificial synapse based on a matrix of the biopolymer ι-carrageenan (ι-car), which exploits Ag dynamics. This artificial synapse emulates the short-term plasticity (STP), paired-pulse facilitation (PPF), and transition from STP to long-term potentiation (LTP) of a biological synapse. The above-mentioned characteristics are realized by exploiting the similarities between the Ag dynamics in the ι-car matrix and the Ca2+ dynamics in a biological synapse. By demonstrating a method that uses biomaterials and Ag dynamics to emulate synaptic functions, this study confirms that ι-car has the potential for constructing neuromorphic systems that use biocompatible artificial synapses.

Development and characterization of muscle-based actuators for self-stabilizing swimming biorobots.

Biorobots that harness the power generated by living muscle cells have recently gained interest as an alternative to traditional mechanical robots. However, robust and reliable operation of these biorobots still remains a challenge. Toward this end, we developed a self-stabilizing swimming biorobot that can maintain its submersion depth, pitch, and roll without external intervention. The biorobot developed in this study utilized a fin-based propulsion mechanism. It consisted of a base made from two composite PDMS materials and a thin PDMS cantilever seeded with a confluent layer of heart muscle cells. The characterization of the heart muscle cell sheet revealed the gradual increase of the dynamic contraction force and the static cell traction force, which was accompanied by a linear increase in the expression levels of contractile and cytoskeletal proteins. In the design of the biorobot, instead of relying only on the geometry, we used two composite PDMS materials whose densities were modulated by adding either microballoons or nickel powder. The use of two materials with different mass densities enabled precise control of the weight distribution to ensure a positive restoration force on the biorobot tilted at any angle. The developed biorobot exhibited unique propulsion modes depending on the resting angle of its "fin" or the cantilever, and achieved a maximum velocity of 142 µm s(-1). The technique described in this study to stabilize and propel the biorobot can pave the way for novel developments in biorobotics.

Hierarchical patterning of multifunctional conducting polymer nanoparticles as a bionic platform for topographic contact guidance.

The use of programmed electrical signals to influence biological events has been a widely accepted clinical methodology for neurostimulation. An optimal biocompatible platform for neural activation efficiently transfers electrical signals across the electrode-cell interface and also incorporates large-area neural guidance conduits. Inherently conducting polymers (ICPs) have emerged as frontrunners as soft biocompatible alternatives to traditionally used metal electrodes, which are highly invasive and elicit tissue damage over long-term implantation. However, fabrication techniques for the ICPs suffer a major bottleneck, which limits their usability and medical translation. Herein, we report that these limitations can be overcome using colloidal chemistry to fabricate multimodal conducting polymer nanoparticles. Furthermore, we demonstrate that these polymer nanoparticles can be precisely assembled into large-area linear conduits using surface chemistry. Finally, we validate that this platform can act as guidance conduits for neurostimulation, whereby the presence of electrical current induces remarkable dendritic axonal sprouting of cells.

Hemocompatibility research on the micro-structure surface of a bionic heart valve.

In order to study how the geometric parameters and shape of the micro-structure surface of a bionic heart valve affects hemocompatibility, mastoid micro-structures with different periodic space were fabricated using a femtosecond laser on a polyurethane (PU) surface. The apparent contact angles of droplets on the micro-structure surfaces were measured to characterize their wettability. Then a series of blood compatibility experiments, including platelet adhesion, dynamic coagulation and hemolysis were completed. The experimental results showed that the micro-structure on the biomaterial surface helped improve its hydrophobicity and hemocompatibility. Also, the periodic space affected not only the hydrophobicity but also the hemocompatibility of the biomaterial. With the increasing of the periodic space, the apparent contact angle increased, the number of platelet adhesion decreased, the dynamic clotting time became longer and the hemolysis ratio reduced. In addition, the shape of the micro-structure also affected the hemocompatibility of the biomaterial.

Nanobionics: the impact of nanotechnology on implantable medical bionic devices.

The nexus of any bionic device can be found at the electrode-cellular interface. Overall efficiency is determined by our ability to transfer electronic information across that interface. The nanostructure imparted to electrodes plays a critical role in controlling the cascade of events that determines the composition and structure of that interface. With commonly used conductors: metals, carbon and organic conducting polymers, a number of approaches that promote control over structure in the nanodomain have emerged in recent years with subsequent studies revealing a critical dependency between nanostructure and cellular behaviour. As we continue to develop our understanding of how to create and characterise electromaterials in the nanodomain, this is expected to have a profound effect on the development of next generation bionic devices. In this review, we focus on advances in fabricating nanostructured electrodes that present new opportunities in the field of medical bionics. We also briefly evaluate the interactions of living cells with the nanostructured electromaterials, in addition to highlighting emerging tools used for nanofabrication and nanocharacterisation of the electrode-cellular interface.

Micromechanical resonator array for an implantable bionic ear.

In this paper we report on a multi-resonant transducer that may be used to replace a traditional speech processor in cochlear implant applications. The transducer, made from an array of micro-machined polymer resonators, is capable of passively splitting sound into its frequency sub-bands without the need for analog-to-digital conversion and subsequent digital processing. Since all bands are mechanically filtered in parallel, there is low latency in the output signals. The simplicity of the device, high channel capability, low power requirements, and small form factor (less than 1 cm) make it a good candidate for a completely implantable bionic ear device.