Mami Tanaka

Development of a PVDF piezopolymer sensor for unconstrained in-sleep cardiorespiratory monitoring

This paper reports the development of an unconstrained sensing technique for monitoring the respiration and heartbeats during sleep using a polyvinylidene fluoride (PVDF) piezopolymer film sensor with the aim that the sensor can be used on the ordinary bed together with the condition that the use of the sensor does not interfere the daily sleep of the patient under measurement. A PVDF film is used as the sensory material in the sensor system. The film is placed under the sheet at the location of the thorax to pick up the fluctuation of the pressure on the bed caused by the respiratory movement and heartbeats. Wavelet multiresolution decomposition analysis is used for the detection of respiration and heartbeat from the sensor output. It is shown that the respiration and heartbeats can simultaneously be detected by the sensor with the use of the wavelet multiresolution decomposition analysis.

The “Haptic Finger”– a new device for monitoring skin condition

Background/aims: Touching the skin is of great importance for the Clinician for assessing roughness, softness, firmness, etc. This type of clinical assessment is very subjective and therefore non‐reproducible from one Clinician to another one or even from time to time for the same Clinician. In order to objectively monitor skin texture, we developed a new sensor, placed directly on the Clinicians finger, which generate some electric signal when slid over the skin surface.

Development of an active palpation sensor for detecting prostatic cancer and hypertrophy

This paper is concerned with the development of an active palpation sensor for detecting prostatic cancer and hypertrophy. The receptor of the sensor is a polyvinylidene fluoride (PVDF) film placed on the surface of a sponge rubber layer. It is mounted on a linear z-translation bar and inserted into the examinees rectum whilst being protected by a medical rubber glove. After being positioned to face the prostate gland, the sensor probe is driven sinusoidally at about 50 Hz, with a peak-to-peak amplitude of 2 mm. The voltage signal from the PVDF film is integrated over the sampling period and is used as the output of the sensor for extracting the features of the collected data. The evaluation of the stiffness by the sensor on 27 normal and unhealthy prostate glands are compared with the results of diagnosis by the doctors palpation. It is shown that the output of the sensor becomes greater with an increase of the stiffness of the prostate gland, which has a good correlation with the doctors evaluation on the stiffness. Further results on the laboratory test reconfirm that the present sensor well discriminates the stiffness of the prostate glands in vivo and non-invasively.

Development of an artificial urethral valve using SMA actuators

The development of an artificial urethral valve for the treatment of urinary incontinence which occurs frequently in the aged is described. The prototype urethral valve is assembled in hand-drum form with four thin shape memory alloy (SMA) (nickel - titanium alloy) plates of 0.3 mm thickness. The shape memory effect in two directions is used to replace the urinary canal sphincter muscles and to control the canal opening and closing functions. The characteristic of the SMA is to assume the shape of a circular arc at normal temperatures and a flat shape at higher temperatures. Experiments have been conducted using a canine bladder and urinary canal.

Measurement and Evaluation of Tactile Sensations using a PVDF Sensor

This study focuses on the measurement and evaluation of tactile sensations of various fabrics. First, tactile data on six pieces of underwear and seven pieces of polo shirts are collected through a questionnaire and the dominant factors of feelings of wearability are determined through factor analysis. Next, a tactile sensor with a polyvinylidene fluoride (PVDF) film as the sensory receptor and a sensor apparatus are assembled. The base of the sensor is an aluminum cylinder, around which a rubber sponge layer, a PVDF film, a protective layer of acetate film, and lace are stacked in sequence. The sensor is set on the rotational axis of a motor and a measurement object is placed on the sensor. Then, the sensor is turned to collect tactile information on the object. Features of the collected data are extracted by calculating the average amplitude of low frequency signals, the variance of sensor output, and the power intensity in a medium frequency range. Comparison with the results shows that the PVDF sensor well describes the human tactile perception.

Development of tactile sensor for monitoring skin conditions

Abstract This paper is concerned with the development of a haptic sensor for monitoring the human skin conditions. The sensor is an assembly of layered media. The base of the sensor is a copper plate, on which a vulcanized rubber, a PVDF film with electrode patches and a protective surface layer of acetate film are stacked in sequence. The sensor is attached onto the tip of an elastic cantilevered beam and pressed against a sample fabric with a prescribed contact force. The beam is translated linearly over the sample fabric with a constant speed to collect the tactile information on the fabric by the piezoceramic sensor. The features on the data are extracted by calculating both the temporal average of the absolute output signal and the intensity of power in the mid-frequency range and plotting then two-dimensionally on the xy -plane. Further the sensor is slid over the human bare skin and the skin with a sticking plaster to see whether the sensor can discriminate the two skin conditions.

Development of a tactile sensor system for reading Braille: fundamental characteristics of the prototype sensor system

This paper is a study on the development of a tactile sensor system for reading Braille. The tactile sensor uses a PVDF (polyvinylidene fluoride) film as the sensory material. The sensor is attached to a slider driven by a DC servomotor and it is slid over a string of Braille with a constant speed to obtain the sensor output. A recognition system of Braille is proposed. In a recognition experiment, the sensor system is verified as to whether it has enough performance to recognize a string of letters appropriately. The obtained result shows that the proposed sensor and sensor system are effective to recognize Braille.

A Wearable Braille Sensor System With a Post Processing

This paper is a study on the development of a wearable sensor system for reading Braille. The study is intended to develop a compact tactile sensor system, which uses a polyvinylidene fluoride (PVDF) film for the sensory receptor. The sensor is mounted onto a fingertip and moved over Braille manually to obtain the output. Since the unsteady movements yield variations in the waveforms, a robust recognition system has been developed. In this study, the post processing is introduced into the recognition system for the improvement of the performance. Two different methods of post processing are developed and examined. In the first method, an appropriate letter string is generated by evaluating the connectivity of letters with information on signals. In the second method, the dictionary in which letter strings are recorded is incorporated as the prior knowledge. Finally, both the methods of post processing are combined to enhance the performance. The combined post processing is incorporated to the wearable sensor system, and the performance of the sensor system is evaluated experimentally. The results show that the sensor system is effective to recognize Braille.

Development of a Sensor System for Measuring Tactile Sensation

This paper presents the development of a sensor system for measuring tactile sensation. First, various tactile feelings of fabrics are collected through questionnaires and the factor analysis is introduced to classify the feelings. Next, an active sensing system using the piezoelectric effect and the pyroelectric effect of a PVDF (polyvinylidene fluoride) film is assembled. The sensors surface is heated and two kinds of active sensing, contact and slide, are introduced to collect tactile information. Measurement is done on the sample fabrics and features of the collected data are extracted as the sensor outputs. Comparison with tactile feelings shows that the sensor system well describes human tactile perception.

Development of soft tribo-sensor using PVDF film for skin surface contour measurement

This paper is concerned with a basic experimental study on the development of a tactile sensor for skin surface contour measurement. The sensor, imitating the finger, was constructed from an aluminum pipe as the digital phalanx, a sponge rubber sheet as the digital pulp and PVDF film as the sensory receptor. Furthermore, the sensor was covered with cellophane tape or a piece of gauze, which seemed to be an effective substitution for a fingerprint. The sensor is supposed to be moved directly along the skin surface and the skin texture would be estimated by measuring the output of the sensor. Since the signals from sensor are complex, three data processing methods, so-called Ten-point Average, Symmetrized Dot Pattern and Wavelet Transform, were introduced to evaluate the surface roughness both qualitatively and quantitatively. The experimental results obtained on some different types of paper and some parts of skin are presented. Furthermore, an efficient visual display technique and a quantitative evaluation method were proposed for the determination of skin roughness. The proposed tactile sensor shows great potential for skin surface contour measurement.