Manabu Chikai

A pilot study of a plantar sensory evaluation system for early screening of diabetic neuropathy in a weight-bearing position.

The purpose of this study is to develop smart equipment to quantify plantar tactile sensibility for the early diagnosis and tracking of peripheral neuropathy caused by diabetes mellitus. In this paper, we offer a new testing system that is composed of a plantar tactile stimulation platform with a small moving contactor to stretch the skin tangentially, a response switch for each tactile stimulus, a motor control box, and a personal computer (PC) for psychophysical data processing. This quantitative sensory testing system has detailed measurements available and is easy to use compared with the conventional testing devices, such as von Frey monofilaments, pin-prick testing devices, and current perception threshold testers. When using our testing system in a weight-bearing position, we observed that the plantar tactile thresholds for the tangential stretching stimulus on the plantar surface of the foot ranged from approximately 10 um to 30 um for healthy subjects. However, the threshold for a subject with diabetes was nearly three times higher than that for healthy subjects. The significant difference between these values suggests that the plantar sensory evaluation system using the lateral skin stretch stimulation can be used for early diagnosis, for the accurate staging of diabetic neuropathy, and for evaluating its progression noninvasively in a clinic and at home.

Evaluation of the variation in sensory test results using Semmes-Weinstein monofilaments.

The purpose of this study is to examine the variability in sensory test of tactile results using Semmes-Weinstein monofilament (SWM). At present, several methods for measuring the tactile sensitivity are clinically used in diabetic peripheral neuropathy screening. One of these methods is a touch test that uses a device with nylon SWMs, i.e., SWMs embedded in a plastic handle. A small pushing force is applied at the handle to bow the filaments. Because of its ease and simplicity, the SWM test is conducted at the patients bedside in a hospital. However, previous studies have reported some problems with this test. Studies have shown variations in the measured data, and it is uncertain whether these variations are caused by mechanical properties of the nylon fiber or by the motion of the operators hands. We carried out two experiments to examine the effect of (1) the variability caused by the human operator conducting the SWM test on the test results and (2) the number of compressions of the SWM on the test results. In experiment 1, we measured the velocity of the operators hand motion and the buckling force of the SWMs. The results showed variability in the hand motion of the operator conducting the SWM tests. In experiment 2, we measured the buckling force of the SWMs under a controlled velocity. We compared the buckling force of the SWMs through a number of trials. These results showed that the buckling force gradually decreases as the number of test cycles increase. In conclusion, we find that the accuracy of the SWM tests is a factor of the number of test cycles. Additionally, manual training for standardizing skills of medical staff members needs to be developed. Furthermore, the characteristics of the SWMs deteriorated over time. In future work, we aimto find a solution to minimize the variability in the SWM test results and develop a new testing system that uses tactile sensibility for diabetic peripheral neuropathy screening.

Application of metal hydride paper to simple pressure generator for use in soft actuator systems.

Metal hydride (MH) actuators have a simple structure and a number of features that make them attractive for use in rehabilitation engineering and assistive technology. The MH actuator provides a high power-to-weight ratio, high-strain actuation, human-compatible softness, and noiseless operation, while being environmentally benign. On the other hand, there remain technical challenges to be overcome to improve the MH actuator regarding its speed of operation and energy efficiency, given the low heat conductivity of the MH powder that is used as the pressure generator for soft actuation. To overcome the issues of low heat conductivity and the handling of MH powder, we developed an MH paper, which is a special paper incorporating MH powder and carbon fiber, for use as a new pressure-generating element for a soft MH actuator system. In addition, the basic properties and structure of the proposed MH paper were investigated through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and several thermodynamic experiments. The results of these experiments showed that the hydrogen absorption and desorption rates of the MH paper were significantly higher than those of the MH powder around room temperature.

An Ergonomic Evaluation of Physical and Mental Loads in Standing-up Motion from Forward-Sloping Toilet Seats

We aim to develop a new in-home assistance system to aid in the standing-up motion from toilet seats in assisted bathrooms. The underlying design concept for accessible toilet facilities is to use a novel compact actuation device—a metal hydride actuator with several unique properties such as softness, noiselessness, and being lightweight—for tilting a toilet seat when required, thus helping elderly or frail people to stand-up after excretion. This ergonomic study evaluates the easiness of the standing-up motion using both objective and subjective data from healthy participants, as a prior step before developing the envisaged toilet seat tilting system. In the experiment, the participants were monitored to obtain simultaneous objective data concerning muscle activity, 3D body motion, center of pressure, and seat pressure distribution. Additionally, all participants were requested to provide subjective data (comfort scores) while standing up from a toilet seat under four different conditions—four different forward-tilting angles (0°, 5°, 10°, and 15°). All participants repeated the motion 25 times for each tilting angle, and provided feedback regarding their standing-up experience and feelings under each condition. According to the collected subjective data, a toilet seat tilt angle of approximately 10° increased the easiness and comfort of the standing-up motion. However, according to the measured objective data, the standing-up motion has individual variations in the electromyogram magnitude, center of pressure excursion, and seat pressure pattern, implying that to analyze the standing-up motion both the measured objective data and the perceived subjective data must be considered.

The Influence of the Manner of Grasping a White Cane on the Ability of Visually Impaired People to Perceive the Texture of Objects

This study examined the relationship between a surface’s texture (i.e., the particle size) and the perception of its roughness obtained from a white cane. The perception of roughness was measured by a magnitude estimation method with nine visually impaired people who used white canes. Their audiovisual information was restricted with eye masks and earmuffs. The perceived texture was investigated with three different styles of grasping the white cane: the index finger grasp, pencil grasp, and thumb grasp. Participants estimated the roughness of 18 waterproof abrasive papers with different particle sizes (6.7 to 279 μm). Because the exponent for this relationship was almost 0.35 for all three grasping styles when the particle size was small, it can be concluded that a small increase in the particle size causes a significant increase in the perceived roughness.

Influence of the Manner of Grasping a White Cane on the Ability of Visually Impaired Persons to Use These Canes for Estimating Object Weights

We have conducted research to obtain fundamental knowledge of the exploration methods used to perceive the characteristics of an object through contact with a white cane. The research has enabled us to examine methods that enhance the accuracy of perceiving objects and the materials and design of a white cane. In this study, we examine whether or not the method of grasping a white cane affects weight perception, with 5 visually impaired people who use white canes in their daily lives as participants. The participants provide estimates for the magnitudes of six weights ranging from 500 g to 1,000 g in steps of 100 g. Results indicate that weight can be determined using a white cane, even though this method is slightly inferior to directly pushing the weight by hand. The weight perception obtained by employing a white cane is not affected by the manner of grasping the cane.