Development of an impulsive motion generator inspired by cocking slip joint of snapping shrimp.

We propose an impulsive motion generator inspired by snapping shrimp. The proposed device mimics the geometrical arrangement of a unique claw joint calledcocking slip jointand integrates it with an artificial rack-pinion actuator mechanism rather than adopting the musculoskeletal system as it is. The design approach allows the proposed device to reproduce the impulsive slip motion through the torque reversal and unlatching mechanism of the underlying unique joint by using a single servo motor. Static and dynamic analyses revealed that the actuator force required to store and release elastic energy was remarkably small compared with the resulting acceleration force and rotation/tip speed. Through simulations and experiments, we validated the mechanical analyses and confirmed that the resulting ultrafast slip motion was comparable with the claw closure of snapping shrimp based on the cocking slip joint. Moreover, from an engineering perspective, the motion profiles are modifiable through design parameters, and the repeatability of the impulsive slip motion is satisfactory.

Generation of Tetrafluoroethylene-Propylene Elastomer-Based Microfluidic Devices for Drug Toxicity and Metabolism Studies.

Polydimethylsiloxane (PDMS) is widely used to fabricate microfluidic organs-on-chips. Using these devices (PDMS-based devices), the mechanical microenvironment of living tissues, such as pulmonary respiration and intestinal peristalsis, can be reproduced in vitro. However, the use of PDMS-based devices in drug discovery research is limited because of their extensive absorption of drugs. In this study, we investigated the feasibility of the tetrafluoroethylene-propylene (FEPM) elastomer to fabricate a hepatocyte-on-a-chip (FEPM-based hepatocyte chip) with lower drug absorption. The FEPM-based hepatocyte chip expressed drug-metabolizing enzymes, drug-conjugating enzymes, and drug transporters. Also, it could produce human albumin. Although the metabolites of midazolam and bufuralol were hardly detected in the PDMS-based hepatocyte chip, they were detected abundantly in the FEPM-based hepatocyte chip. Finally, coumarin-induced hepatocyte cytotoxicity was less severe in the PDMS-based hepatocyte chip than in the FEPM-based hepatocyte chip, reflecting the different drug absorptions of the two chips. In conclusion, the FEPM-based hepatocyte chip could be a useful tool in drug discovery research, including drug metabolism and toxicity studies.

Tetrafluoroethylene-Propylene Elastomer for Fabrication of Microfluidic Organs-on-Chips Resistant to Drug Absorption.

Organs-on-chips are microfluidic devices typically fabricated from polydimethylsiloxane (PDMS). Since PDMS has many attractive properties including high optical clarity and compliance, PDMS is very useful for cell culture applications; however, PDMS possesses a significant drawback in that small hydrophobic molecules are strongly absorbed. This drawback hinders widespread use of PDMS-based devices for drug discovery and development. Here, we describe a microfluidic cell culture system made of a tetrafluoroethylene-propylene (FEPM) elastomer. We demonstrated that FEPM does not absorb small hydrophobic compounds including rhodamine B and three types of drugs, nifedipine, coumarin, and Bay K8644, whereas PDMS absorbs them strongly. The device consists of two FEPM layers of microchannels separated by a thin collagen vitrigel membrane. Since FEPM is flexible and biocompatible, this microfluidic device can be used to culture cells while applying mechanical strain. When human umbilical vein endothelial cells (HUVECs) were subjected to cyclic strain (~10%) for 4 h in this device, HUVECs reoriented and aligned perpendicularly in response to the cyclic stretch. Moreover, we demonstrated that this device can be used to replicate the epithelial-endothelial interface as well as to provide physiological mechanical strain and fluid flow. This method offers a robust platform to produce organs-on-chips for drug discovery and development.

Wearable Kinesthetic I/O Device for Sharing Wrist Joint Stiffness.

In this paper, we developed a wearable kinesthetic I/O system, which is able to share wrist joint stiffness by measuring and intervening in four muscle activities on the forearm simultaneously through the same electrodes. This achieves interactive peg rehabilitation by sharing muscle activities among patients and therapists. Through the performance study, it was shown that 1) applied EMS and measured wrist joint stiffness, and 2) produced wrist joint stiffness and measured EMG value has a linear correlation, which allows designing a mapping function between the measured EMG value on one person and the EMS value applied to another person. In a perceptual study, which shared the wrist stiffness between two persons, participants were able to recognize the level of their confederate's wrist joint stiffness using a 4-point Likert scale linearly. The developed system would benefit a physical therapist and a patient for sharing their wrist stiffness and grip force, which are usually difficult to be observed in a visual contact.

Human Wrist Impedance Estimation Based on Impulse Response Induced by Snap-Through Buckling of Closed-Elastica.

A human joint impedance estimation method employing a wearable device using the snap-through buckling of closed-elastica has been proposed in our previous study and tested for the ankle joint. In the present study, the method is applied to the wrist impedance estimation scheme. Our method aims at the task-dependent scenarios. The wrist joint is involved in a variety of tasks, where the impedance plays a key role in physical interaction with environments. Because of the unique design and actuation concept, the proposed device does not disrupt the voluntary movements of the wrist and can be used in the estimation during the user's own motion planning. In this paper, to verify our method, the wrist impedance under the quasi-stationary condition is estimated, and the results are compared with the related works. Also, we discuss the profiles of the induced impulse responses and suggest an alternative estimation manner which does not require any force (torque) information.

Optimized Design of a Variable Viscosity Link for Robotic AFO.

Herein we present the development of a novel Ankle Foot Orthosis for gait support of people with foot-drop symptoms. The developed AFO uses an elastic link mechanism to brake the ankle joint during initial contact, thus mitigating foot-slap, and an integrated energy store-and-release mechanism to support toe lift in the swing phase, thus mitigating toe-drag. This paper presents improvements in the braking-holding power of the elastic link mechanism over its previous version, the torque-angle characteristics of the developed AFO with the renewed elastic link, and a pilot test with one person with foot-drop symptoms to verify the proposed functions of the developed AFO.

Tarsusmeter: Development of a wearable device for ankle joint impedance estimation.

We present the development and basic evaluation of a new wearable device for estimation of ankle joint impedance called Tarsusmeter. The device is intended for application with persons with locomotion disabilities to quantify the ankle joint impedance, especially in cases of spasticity where the joint's impedance is expected to differ significantly from healthy persons. The lack of a simple and light weight solution to provide objective evaluation of ankle joint impedance motivates the design criteria of this device to be as such. The target application is also to quantify variable stiffness actuator based orthosis in-vivo. Thus the form factor avoids overlap with custom shapes of such orthosis. The paper presents the mechanical design of the device, physical simulations to characterize the device-leg system, the used algorithm for impedance parameter estimation, and preliminary testing of the device.

Mutual interference between intramolecular proton transfer sites through the adjoining π-conjugated system in Schiff bases of double-headed, fused salicylaldehydes.

We synthesized two constitutionally isomeric bis(iminomethyl)-2,6-dihydroxynaphthalenes, namely, α,α-diimines 1 and ß,ß-diimines 2, which can be formally represented as fused salicylaldimines with resonance-assisted hydrogen-bonding sites. Spectroscopic data show that the OH/OH, NH/OH, and NH/NH forms of 1 were in equilibrium in solution and that the proportion of the NH-bearing tautomers increased as the solvent polarity increased. The UV spectra of thin solid films of 1 with various types of hydrogen-bonding networks differed from one another, and the spectral profiles were markedly temperature dependent, whereas the spectra of 1 in the molten state showed quite similar profiles. In contrast, 2 existed predominantly as the OH/OH form irrespective of the solvent polarity or crystal packing. Quantum chemical calculations suggest that the difference between the probabilities of intramolecular proton transfer in 1 and 2 can be explained in terms of the interplay between the resonance-assisted hydrogen-bonding sites and the adjoining π-conjugated system.

Facile preparation of a fully π-conjugated metallopolymer composed of fused salphen complexes.

Novel π-conjugated compounds composed of fused salphen groups as a repeating unit, embedded with four or an indefinite number of zinc nuclei have been synthesized. The solid-state absorption spectra, IR spectra, and powder XRD patterns of these compounds are investigated and compared with those of analogous oligomers. The presumptive polymer contains at least five units of the salphen complex and its assembly is highly ordered in the solid state.