User's Skin Research Articles

Powered by sweat: Throw out the batteries: Biofuels will change the future of wearable devices

Admit it-you love your smart watch and all the amazing things you can do with it. But the task of keeping it charged can be annoying. A longer battery life would be great-but with batteries, the amount of energy stored correlates with volume, and bigger batteries add bulk and weight. All wearables, including fitness trackers, audio-enhancing hearables that go in your ear, and augmented-reality contact lenses, have a similar power problem. And today's batteries are too bulky and stiff for use in wearables that are woven into textiles or directly mounted on a user's skin.

Design, Development, and Validation of a Self-Aligning Mechanism for High-Torque Powered Knee Exoskeletons

Powered knee exoskeletons aim to assist individuals with lower limb impairments by providing power and torque at the joint level. However, if the anatomical and exoskeleton joints are not perfectly aligned, the exoskeleton assistance may result in spurious forces and torques transferred to the user's limb. These spurious forces and torques can then generate undesired loads on the user's joint and shear stress on the user's skin, causing pain and ultimately undermining the exoskeleton assistance. To address this issue, we propose a novel powered knee exoskeleton with a self-aligning mechanism using a prismatic-revolute-revolute (PRR) configuration. The proposed self-aligning mechanism weighs 190 g (i.e., 5.3% of the total exoskeleton weight) and can transmit up to 120 Nm of torque at the knee joint (i.e., biological peak torque for a 50th percentile male climbing stairs). Our experiments show that during assisted sit-to-stand transfers the peaks of the spurious torques and forces are below 0.5 Nm and 5 N, respectively, even if misalignments are intentionally added between the user and the exoskeleton. This study supports the use of self-aligning mechanisms in powered exoskeletons.

Two-Dimensional Thermal Haptic Module Based on a Flexible Thermoelectric Device.

In this study, we introduce a haptic communication method using two-dimensional (2D) arrayed thermal haptic module. The 2D thermal haptic module delivers real-time information to user through the thermoception of the user's skin. Such 2D thermal haptic module could be realized using flexible thermoelectric (TE) device and independent temperature control of individual unit cell that are arranged in the form of 2D array. The independent temperature control and access to the specific TE unit cell could be achieved using active matrix addressing and serial H-bridge circuit. For the optimal design of the 2D thermal haptic module, an analysis of the spatial precision of human sense on temperature has been implemented. As a demonstration, the 2D thermal haptic module is attached to blind-assistive cane to inform the position of obstacles to the user. This study demonstrates that the flexible TE device can find a new application field as an information transfer tool, not only just as an energy generator or cooler, which are the conventional applications of TE device.

PUMAH: Pan-Tilt Ultrasound Mid-Air Haptics for Larger Interaction Workspace in Virtual Reality.

Mid-air haptic interfaces are promising tools for providing tactile feedback in Virtual Reality (VR) applications, as they do not require the user to be tethered to, hold, or wear any system or device. Currently, focused ultrasound phased arrays are the most mature solution for providing mid-air haptic feedback. They modulate the phase of an array of ultrasound emitters so as to generate focused points of oscillating high pressure, eliciting vibrotactile sensations when encountering a user's skin. While these arrays feature a reasonably large vertical workspace, they are not capable of displaying stimuli far beyond their horizontal limits, severely limiting their workspace in the lateral dimensions. In this paper, we propose an innovative low-cost solution for enlarging the workspace of focused ultrasound arrays. It features two degrees of freedom, rotating the array around the pan and tilt axes, thereby significantly increasing the usable workspace and enabling multi-directional feedback. Our hardware tests and human subject study in an ecological VR setting show a 14-fold increase in workspace volume, with focal point repositioning speeds over 0.85 m/s while delivering tactile feedback with positional accuracy below 18 mm. Finally, we propose a representative use case to exemplify the potential of our system for VR applications.

Relaying the High-Frequency Contents of Tactile Feedback to Robotic Prosthesis Users: Design, Filtering, Implementation, and Validation

It is known that high-frequency tactile information conveys useful cues to discriminate important contact properties for manipulation, such as first contact and roughness. Despite this, no practical system, implementing a modality matching paradigm, has been developed so far to convey this information to users of upper-limb prostheses. The main obstacle to this implementation is the presence of unwanted vibrations generated by the artificial limb mechanics, which are not related to any haptic exploration task. In this letter, we describe the design of a digital system that can record accelerations from the fingers of an artificial hand and reproduce them on the user's skin through voice-coil actuators. Particular attention has been devoted to the design of the filter, needed to cancel all those vibrations measured by the sensors that do not convey information on meaningful contact events. The performance of the newly designed filter is also compared with the state of the art. Exploratory experiments with prosthesis users have identified some applications where this kind of feedback could lead to sensory-motor performance enhancement. Results show that the proposed system improves the perception of object-salient features such as first-contact events, roughness, and shape.

Design and Validation of a New PPG Module to Acquire High-Quality Physiological Signals for High-Accuracy Biomedical Sensing

A new photoplethysmography (PPG) module is designed, optimized, and fabricated in this study to obtain quality PPG signal for high-accuracy bio-sensing. The module contains four light emitting diodes (LEDs) in wavelengths of 530, 660, 850, and 940 nm and a photo-diode (PD). The distances between LEDs and PD are optimized for quality PPG signals via maximizing the ratios of pulsatile (ac) to non-pulsatile (dc) components in PPG waveforms. The optimization is carried out based on an establishment of a complete optical model that simulates well optics under the user's skin based on Beer–Lambert law. In results, the optimal LED/PD distances that lead to maximal ac/dc ratios of PPGs for different wavelengths are derived. With the optimal LEDs/PD distances in hand, a new PPG module is designed and fabricated subsequently, and further installed in a hand-held blood pressure (BP) sensing device for performance validation. Based on experimental results, for the PPG module, an ac/dc ratio of 8.02% is achieved by the proposed PPG module as opposed to 6.74% and 6.90% by two other commercial modules. As for sensing BP based on reflective pules transient time, the error is controlled well with the mean difference (MD) and standard deviation (SD) as −1.16 ± 5.38 (MD±SD) and −0.53 ± 1.92 mmHg, respectively, for systolic blood pressure and diastolic blood pressure. The resulted accuracy successfully categories the developed PPG sensor among the bests by Association for the Advancement of Medical Instrumentation and British Hypertension Society.

Aerial Vibrotactile Display Based on MultiUnit Ultrasound Phased Array.

In this paper, we report on an airborne vibrotactile display with a multiunit ultrasound phased array synthetic aperture. The system generates an ultrasound field with a location-tunable focus in the air, which exerts time-variant acoustic radiation pressure on the user's skin, resulting in perceivable localized vibrotactile stimuli. The paper contains three major new contributions from previous related works. The first is an experimental validation of large-aperture focusing with improved synchronization offering an enlarged workspace in which sufficient acoustic power concentration is guaranteed. From the experiments, it is expected that perceivable vibrotactile focus can be generated 1 m away from a four-unit array system. The second is an experimental evaluation of the presented pressure for producing a broad variety of tactile perception, which shows that the generated ultrasound focus can serve as an vibrotactile actuator that has flat frequency characteristics in the domain of perceptual stimuli. The third is a psychophysical result of the detection threshold curve for sinusoidal stimuli offered by the system. The obtained curve shows similarity with conventionally known results, which have minimum values at approximately 200 Hz.

複数の振動刺激を用いた運動方向呈示による手首の運動誘導

We propose a novel method for motion guidance by creating a motion direction by using multiple vibration stimulations. In order to create the motion direction, we utilize a vibratactile illusion called Phantom Sensation. In this method, moving vibration stimulation on the user's skin, which is generated by controlled the position of Phantom Sensation, creates the motion direction. In this paper, we guide the user's wrist to the desired position using our proposal method. We control the produced direction and transmission time by the relationship between current position and desired position. We recognize that they can arrive at a desired position to move their wrist obeying the produced direction.

J1610105 ウェアラブル皮膚振動センサの応用に関する基礎検討 : 接触力がセンサ出力に及ぼす影響

We have developed a wearable tactile sensor using a PVDF film, which detects skin-propagated vibration based on the mechanical interaction between the fingertip and the object. The sensor allows users to touch the object with bare fingertips. The output from this sensor involves in each user's skin mechanical properties as well as touch object and behavior such as contact force and scanning velocity. The sensor has a potential of the evaluation of individual tactile sensations and tactile communications. In this paper, influence of the contact force on the sensor output is investigated. The result shows that the contact force affects the intensity and frequency response of the sensor output.

A machine learning approach to improve contactless heart rate monitoring using a webcam.

Unobtrusive, contactless recordings of physiological signals are very important for many health and human-computer interaction applications. Most current systems require sensors which intrusively touch the user's skin. Recent advances in contact-free physiological signals open the door to many new types of applications. This technology promises to measure heart rate (HR) and respiration using video only. The effectiveness of this technology, its limitations, and ways of overcoming them deserves particular attention. In this paper, we evaluate this technique for measuring HR in a controlled situation, in a naturalistic computer interaction session, and in an exercise situation. For comparison, HR was measured simultaneously using an electrocardiography device during all sessions. The results replicated the published results in controlled situations, but show that they cannot yet be considered as a valid measure of HR in naturalistic human-computer interaction. We propose a machine learning approach to improve the accuracy of HR detection in naturalistic measurements. The results demonstrate that the root mean squared error is reduced from 43.76 to 3.64 beats/min using the proposed method.

2A2-A13 温冷刺激を用いたローラー型痒み抑制器の開発(触覚と力覚(2))

Painful thermal stimulation is known to relieve itch, which is a significant problem in many diseases. We focused on thermal grill illusion and synthetic heat, which are well-known phenomena that can generate pain or burning sensation without physical damage; we tried to achieve a similar effect via a harmless-range thermal stimulation. We developed a roller-type itch-relief device. When the device is rolled onto the user's skin, the skin is alternately exposed to hot and cold stimuli. The roller is composed of aluminum parts. One part is set to hot and the other is set to cold by embedded Peltier devices. When the device is rolled on the user's skin, the skin is alternately exposed to hot and cold stimuli. In addition, vibration is applied so that a virtual scratching feeling is presented without damage to the skin. We evaluated the device by eliciting an itch using a lactic acid solution and then applying the device. The results showed that the device provides effective temporal relief from itch and that its effect continues for a few minutes.

31.1: Invited Paper: Programmable Electrostatic Surface for Tactile Perceptions

AbstractWe describe a fully programmable Electrostatic Tactile (ET) feedback system that delivers a range of tactile textures to a mobile display. The ET system is a robust, thin, and optically transparent structure that can be overlaid unobtrusively on top of a display screen. The system exploits the phenomenon of electrovibration to create a controllable frictional force between a user's fingertip and the surface. The system enables the realization of localized tactile information delivered to the user's skin directly, without moving parts. A tactile image is formed in accordance with the visual information displayed (virtual textures, tactile silhouettes, etc.). The magnitude and pattern of the frictional force on the display can be programmed to correspond to the images shown on the display and actual coordinates of the touch interaction in real time. This has been achieved using a variety of different materials, including those that are compatible with flexible devices.

Analysis of primary aromatic amines originated from azo dyes in commercial textile products in Japan

The purpose of this study was to clarify the actual condition of 26 types of carcinogenic primary aromatic amines (PAAs) originated from azo dyes in commercial textile products in Japan. In the case of textiles made of various fibers of various colors, the fibers were separated by color and analyzed. A total of 86 textile products (117 samples) were analyzed. Twenty-one kinds of PAAs were detected in the samples and almost all the PAAs were detected at low concentrations. However, the concentrations of benzidine, 3,3′-dimethoxybenzidine, and 2,4-diaminotoluene (56–440 μg g−1) in placemats made of cotton were found to exceed EU regulation limits of 30 μg g−1. Although such placemats do not always come into contact with the user's skin, it is thought that they should be handled more carefully. Finally, 7 products (8 samples) contained PAAs at concentrations that exceeded the regulation limits. Two sample preparation methods (with and without solvent extraction) were performed on the same sample in order to compare the PAAs in samples in which it is difficult to separate the component materials, such as a cotton fabric that contained polyester fibers. In a comparison of the results obtained from the two methods, it was observed that the concentrations and/or kinds of PAAs detected in the samples were different. It was therefore thought that textile products that present this particular challenge should be analyzed by both methods.

Study on Dyeing Behavior of Cotton/Organic Cotton Knitted Fabrics

Organic cotton is grown using methods and materials that have a low impact on the environment. Organic cotton is grown and processed without toxic chemicals that can be absorbed easily when in contact with the user's skin. This paper describes the dyeing behavior of organic cotton vs conventional cotton to find what will be the significance between them. The ring spun yarns of 40s combed organic (GOTS certified) and ordinary cotton were produced with similar parameters like beating point and settings. Knitted fabrics were produced with similar loop length and weight using organic and ordinary cotton yarn. Both the fabrics were processed in GOTS certified Processing unit using reactive dyes in soft flow machine in single dye bath. Processed fabrics were tested for colour fastness to washing, water, rubbing, perspiration and light. Colour difference and strength were also measured using Spectrophotometer (DATACOLOUR). Presence of metals were also analyzed in both the processed fabrics and reported here.

An EMG-Based Robot Control Scheme Robust to Time-Varying EMG Signal Features

Human-robot control interfaces have received increased attention during the past decades. With the introduction of robots in everyday life, especially in providing services to people with special needs (i.e., elderly, people with impairments, or people with disabilities), there is a strong necessity for simple and natural control interfaces. In this paper, electromyographic (EMG) signals from muscles of the human upper limb are used as the control interface between the user and a robot arm. EMG signals are recorded using surface EMG electrodes placed on the user's skin, making the user's upper limb free of bulky interface sensors or machinery usually found in conventional human-controlled systems. The proposed interface allows the user to control in real time an anthropomorphic robot arm in 3-D space, using upper limb motion estimates based only on EMG recordings. Moreover, the proposed interface is robust to EMG changes with respect to time, mainly caused by muscle fatigue or adjustments of contraction level. The efficiency of the method is assessed through real-time experiments, including random arm motions in the 3-D space with variable hand speed profiles.

Investigation of Rotational Skin Stretch for Proprioceptive Feedback With Application to Myoelectric Systems

We present a new wearable haptic device that provides a sense of position and motion by inducing rotational skin stretch on the user's skin. In the experiments described in this paper, the device was used to provide proprioceptive feedback from a virtual prosthetic arm controlled with myoelectric sensors on the bicep and tricep muscles in 15 able-bodied participants. Targeting errors in blind movements with the haptic device were compared to cases where no feedback and contralateral proprioception were provided. Average errors were lower with the device than with no feedback but larger than with contralateral proprioceptive feedback. Participants also had lower visual demand with the device than with no feedback while tracking a 30 ( degrees ) moving range. The results indicate that the rotational skin stretch may ultimately be effective for proprioceptive feedback in myoelectric prostheses, particularly when vision is otherwise occupied.

Reintroduction of a classic vitamin D ultraviolet source

As early as 1930 sunlamps claiming to provide ultraviolet (UV) exposure to make vitamin D were sold to the public in the US and Canada for home use. Today even with dietary supplementation of vitamin D many people do not get enough solar UV exposure to maintain sufficient vitamin D levels. There is growing interest in the availability of sunlamps for this purpose. The original Sperti Sunlamp, with label claiming vitamin D benefit was approved by the American Medical Association in 1940 as a sunlamp. This intermediate pressure mercury lamps ultraviolet B emission lines, at 297, 302, and 313nm are able to convert 7-dehydrocholesterol in the skin to vitamin pre-D3 initiating the natural process of vitamin D formation. Today's KBD Vitamin D lamp, an updated model of the earlier type source. In order to comply with modern safety guidance, the source is filtered to remove unnecessary UVC radiation and is equipped with a timer to control the dose administered. The 5min timer provides an exposure, at 20in. from the user's skin, of one standard erythemal dose (SED). The SED represents a suberythemal dose for even the most sensitive skin type I individual.

Personal communications apparatus

A personal communications apparatus comprises a first part, having a microphone (114), and a second part, having a loudspeaker (118). The first part is adapted to be worn on a user's wrist (202) and the second part is adapted to be worn on their finger. In use, the user's hand is held up to the side of their head, thereby placing the microphone (114) adjacent to their mouth and the loudspeaker (118) adjacent to their ear. Communication between first and second parts of the apparatus is by means of signals transmitted via the user's skin. In a non-illustrated embodiment the second part is adapted to be worn on the ear.