A biomimetic underwater microrobot with multifunctional locomotion

Underwater microrobots are in urgent demand for applications such as pollution detection and video mapping in limited space. Compact structure, multi-functionality, and flexibility are normally considered incompatible characteristics for underwater microrobots. Nevertheless, to accomplish our objectives, we designed a novel inchworm-inspired biomimetic locomotion prototype with ionic polymer metal composite (IPMC) actuators, and conducted experiments to evaluate its crawling speed on a flat underwater surface. Based on this type of biomimetic locomotion, we introduced a new type of underwater microrobot, using ten IPMC actuators as legs or fingers to implement walking, rotating, floating, and grasping motions. We analysed the walking mechanism of the microrobot and calculated its theoretical walking speed. We then constructed a prototype of the microrobot, and carried out a series of experiments to evaluate its walking and floating speeds. Diving/surfacing experiments were also performed by electrolysing the water around the surfaces of the actuators. The microrobot used six of its actuators to grasp small objects while walking or floating. To implement closed-loop control, we employed three proximity sensors on the microrobot to detect an object or avoid an obstacle while walking.     

ESTIMATION OF IRREDUCIBLE WATER SATURATION AND EFFECTIVE PORE SIZE OF MUDSTONES

A theoretical consideration of immobile water saturation in mudstone is made by means of a capillary model of a porous medium using the air and water absolute permeabilities of a sample. The calculated values of immobile water saturation of the Tertiary mudstones from Japan tend to support a generally-accepted concept; virtually all the water in mudstones is irreducible. Immobile or irreducible water saturation increases gradually with decrease of porosity of mudstones; 15% porosity is a critical value beyond which mudstones contain 100% immobile water in the pores.
Pore sizes of the mudstones estimated by the same model are considerably greater than those estimated by Welte (1972), and are more comparable with Momper's (1978) atypical pore size range of mudstone. The result of analysis indicates that radius of principal pores of the mudstones, which are effective on fluid flow, ranges from about 0.1–0.5 μm. The result thus suggests that even relatively large hydrocarbon molecules can effectively pass through the rock.     

Effect of pre-nitridation treatment on the formation of anatase TiO2 films by anodization

High performance-anatase TiO₂ films were successfully formed on metallic titanium by anodization in an acidic electrolyte composed of H₂SO₄, H₃PO₄ and H₂O₂ subsequent to pre-nitridation treatment. The pre-nitridation treatment was carried out by pre-annealing metallic titanium under a nitrogen atmosphere of 0.1 MPa. The anodized films showed photocatalytic activity in photooxidization of the iodide anion into the tri-iodide anion. The nitridation treatment had a significant effect not only on the formation of anatase TiO₂ films but also on the photocatalytic activity of the anodized films.     

The effects of Li salts on the performance of a polymer actuator based on single-walled carbon nanotube-ionic liquid gel

The effects of Li salts (Lithium tetrafluoroborate (Li[BF₄]) and Lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI])) on the electrochemical and electromechanical properties of an actuator using a polymer-supported single-walled carbon nanotube (SWCNT)-ionic liquid (IL) gel electrode were investigated. The ionic conductivities of the gel electrolyte layers with molar ratios of Li[BF₄]/1-ethlyl-3-methylimidazolium tetrafluoroborate (EMI[BF₄]) = 0.1 and 0.5, and Li[TFSI]/1-ethlyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI[TFSI]) = 0.1 and 0.3 were higher than those containing only EMI[BF₄] and only EMI[TFSI], respectively. We found a large capacitance value 65-96 F/g at a slow sweep rate 1 mV s⁻¹. The actuator containing Li salt/IL performed much better than that containing only IL. It is considered that the higher ionic conductivity of the gel electrolyte layer containing Li salt/IL produces the quick response actuator, and that the large capacitance gives a large generated strain.     

A new type of hybrid fish-like microrobot

In order to develop a new type of fish-like microrobot with swimming, walking, and floating motions, in our past research, we developed a hybrid microrobot actuated by ionic conducting polymer film (ICPF) actuators. But the microrobot had some problems in walking and floating motions. In this paper, we propose a concept of hybrid microrobot (see Fig. 1). The microrobot is actuated by a pair of caudal fins, a base with legs and an array of artificial swim bladders. We have developed a prototype of the base with legs and one artificial swim bladder, respectively, and carried out experiments for evaluating their characteristics. Experimental results show the base with legs can realize walking speed of 6 mm/s and rotating speed of 7.1 degrees/s respectively, and the prototype of the artificial swim bladder has a maximum floatage of 2.6 mN. The experimental results also indicate that the microrobot has some advantages, such as walking motion with 2 degrees of freedom, the walking ability on rough surface (sand paper), the controllable floatage, etc. This kind of fish-like microrobot is expected for industrial and medical applications.     

Dynamic fracture analysis of a transverse wedge-loaded compact specimen

The J-integral method cannot be applied to the elastic plastic dynamic crack propagation, because unloading and inertia force may take place. From this point of view dynamic elastic plastic scheme using J-integral is developed.Using this dynamic finite element program an MRL type specimen is analyzed. As the result, the property of path-independence of the J-integral under the existence of inertia force and unloading is confirmed. Dynamic effects are considerably small in the MRL type specimen. Also the influence of plastic zone on the crack arrest toughness is shown.Finally the present result is compared with the request of ASTM 2nd round robin test program for crack arrest toughness.     

Electrolyzed–Reduced Water: Review I. Molecular Hydrogen Is the Exclusive Agent Responsible for the Therapeutic Effects

Numerous benefits have been attributed to alkaline-electrolyzed–reduced water (ERW). Sometimes these claims are associated with easily debunked concepts. The observed benefits have been conjectured to be due to the intrinsic properties of ERW (e.g., negative oxidation–reduction potential (ORP), alkaline pH, H₂ gas), as well enigmatic characteristics (e.g., altered water structure, microclusters, free electrons, active hydrogen, mineral hydrides). The associated pseudoscientific marketing has contributed to the reluctance of mainstream science to accept ERW as having biological effects. Finally, through many in vitro and in vivo studies, each one of these propositions was examined and refuted one-by-one until it was conclusively demonstrated that H₂ was the exclusive agent responsible for both the negative ORP and the observed therapeutic effects of ERW. This article briefly apprised the history of ERW and comprehensively reviewed the sequential research demonstrating the importance of H₂. We illustrated that the effects of ERW could be readily explained by the known biological effects of H₂ and by utilizing conventional chemistry without requiring any metaphysical conjecture (e.g., microclustering, free electrons, etc.) or reliance on implausible notions (e.g., alkaline water neutralizes acidic waste). The H₂ concentration of ERW should be measured to ensure it is comparable to those used in clinical studies.     

Secreted Signaling Molecules at the Neuromuscular Junction in Physiology and Pathology

Signal transduction at the neuromuscular junction (NMJ) is affected in many human diseases, including congenital myasthenic syndromes (CMS), myasthenia gravis, Lambert–Eaton myasthenic syndrome, Isaacs’ syndrome, Schwartz–Jampel syndrome, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. The NMJ is a prototypic cholinergic synapse between the motor neuron and the skeletal muscle. Synaptogenesis of the NMJ has been extensively studied, which has also been extrapolated to further understand synapse formation in the central nervous system. Studies of genetically engineered mice have disclosed crucial roles of secreted molecules in the development and maintenance of the NMJ. In this review, we focus on the secreted signaling molecules which regulate the clustering of acetylcholine receptors (AChRs) at the NMJ. We first discuss the signaling pathway comprised of neural agrin and its receptors, low-density lipoprotein receptor-related protein 4 (Lrp4) and muscle-specific receptor tyrosine kinase (MuSK). This pathway drives the clustering of acetylcholine receptors (AChRs) to ensure efficient signal transduction at the NMJ. We also discuss three secreted molecules (Rspo2, Fgf18, and connective tissue growth factor (Ctgf)) that we recently identified in the Wnt/β-catenin and fibroblast growth factors (FGF) signaling pathways. The three secreted molecules facilitate the clustering of AChRs by enhancing the agrin-Lrp4-MuSK signaling pathway.