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Effects of AC current (15-100Hz) on the human body when it passes from the left hand to the feet. (The figure is referenced from IEC TS 60479-1 ed.4.1 3 [62].)
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The human body has unique electrical characteristics. These characteristics have been investigated in various studies in human-computer interaction (HCI) and related research fields. Such studies include applications for using the body as a conductive lead for transmission or electric field sensing and activating human muscles or organs. However, e...
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... to the International Electrotechnical Commission (IEC) [62], the important element in considering electric shock is the amount of current passing through the body. With a 15-100Hz AC signal (such as in commercial power supplies collected from plugs [64]), humans do not perceive less than 0.5mA of current (Figure 3). In fact, currents of to 10mA do not pose a serious risk to Table 2. Reference Levels of Time-Varying Contact Currents from Conductive Objects (The Table is Referenced from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Guidelines [65], Table 8 Exposure characteristics Frequency range Maximum contact current (mA)* Up to 2.5kHz ...
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... AC signals can cause electric shock. For low-frequency AC signals, especially signals up to 100Hz, the allowed current is shown in Figure 3. In general, the value considered as the threshold in most studies is 0.5mA. ...
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... low-frequency power, continuous current passing through the body for a few seconds may be risky. Figure 3 displays the effects of time and current value. For example, when a 10mA current passes through the body, the risk is AC-2 per instance of use; however, the risk becomes AC-3 if the current is applied for more than 2,000ms. ...
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... they also state that further studies are required and that the effects of long-term usage are unknown. Figure 3 is useful when we consider treating currents of more than 10ms. However, in case of a shorter duration, currents up to 1,000mA has a low risk of fibrillation (up to 5% possibility) [63]. ...
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... threshold for harm that can occur as a result of electricity passing through the body depends on the route of the flow. In IEC 60479-1, the heart current factor is defined with respect to the values on the path from the left hand to the feet, as displayed in Figure 3 [62,67,181]. The risk of ventricular fibrillation for current paths other than that from the left hand to the feet can be calculated using I x = I r /F . ...
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... frequencies reported in the work are in the range 50-80Hz (AC). Referring to Figure 3, such frequencies can be considered as the most dangerous. However, the current used in REVEL is reported to be 150μA. ...
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... the current used in REVEL is reported to be 150μA. In cases of frequencies below 2.5kHz, the safety threshold is 0.5mA (see Figure 3 and Table 2). In addition, the resulting heart current factor (from Table 3) is 0.8-1.0, and therefore the current value used in REVEL can be considered safe. ...
Citations
... Figure 1 shows the waveforms that we used. We created these with safety in mind, referring to the study of design guidelines [26]. For normal EMS, we used the pulse wave with a width of 0.6 ms. ...
Currently, visual Augmented Reality (AR) technology is widespread among the public. Similarly, haptic AR technology is also widely practiced in the academic field. However, conventional haptic AR devices are not suitable for interacting with real objects. These devices are often held by the users, and they contact the real object via the devices. Thus, they prevent direct contact between the user and real objects. To solve this problem, we proposed employing Electrical Muscle Stimulation (EMS) technology. EMS technology does not interfere with the interaction between the user and the real object, and the user can wear the device. First, we examined proper stimulus waveforms for EMS, in addition to pulse waveforms. At the same time, we examined the appropriate frequency and pulse width. The waveforms that we used this time were a sawtooth wave, a reverse sawtooth wave, and a sine wave. Second, to clarify the characteristic of the force presented by the EMS, we measured the relationship between the input voltage and the force presented and obtained the point of subjective equality using the constant method. Subsequently, we presented the bump sensation using EMS to the participants and verified its effectiveness by comparing it with the existing methods.
... In this study, it was assumed that it was sufficient to present force in the direction of bending the subject's wrist and that the EMS should be used with a maximum current of about 10 mA, considering the amount of current that would not affect the human body according to Kono et al. [10] The maximum electrical resistance of the human body was assumed to be about 10 kΩ, which means that an electrical voltage of about 100 V is required. ...
... Kono et al. [10] have shown that this amount of current does not pose any problem to the human body. The stabilizing power supply applied a voltage of 15 V to the boost type DCDC converter, and the output of the boost type DCDC converter was designed to output up to 200 V. ...
We propose a learning support system with extremely low latency and low cognitive load to correct the user’s motion. In previous studies, visual and haptic feedback has been mainly used to support motion learning, but there is a delay between the presentation of the stimulus and the modification of the action. However, this delay is due to reaction time and cognitive load and is difficult to shorten. This study proposed a system for solving this problem by combining Electrical Muscle Stimulation (EMS) and prediction of the user’s motion. In order to improve the control ability of the underhand throwing, we used the system to tell the subject the release point during the underhand throwing motion and verified the learning effect. This experiment revealed that EMS tended to be effective in teaching the ball’s release point, although it did not improve the control ability of the underhand throwing motion. In addition, although the effectiveness of EMS for motion learning was not yet fully evaluated, this study showed the possibility of applying EMS to support learning of motion.
... NMES is considered a safe technique relative to other electrical stimulation techniques commonly used in psychological research (e.g., transcranial Altering and Direct Current Stimulation). Indeed, the possibility of inducing injuries with NMES is low, as long as the stimulation parameters are carefully selected [8], the device used complies with the International Electrotechnical Commission guidelines [9], and administrators are trained to follow safety guidelines [10]. Outside of the face, there has been only one reported case of burns as a result of deviation from the established protocol [11]. ...
Facial neuromuscular electrical stimulation (NMES) is the application of an electrical current to the skin to induce muscle contractions and has enormous potential for basic research and clinical intervention in psychology and neuroscience. Because the technique remains largely unknown, and the prospect of receiving electricity to the face can be daunting, willingness to receive facial NMES is likely to be low and gender differences might exist in the amount of concern for the sensation of pain and skin burns. We investigated these questions in 182 healthy participants. The likelihood of taking part (LOTP) in a hypothetical facial NMES study was measured both before and after presenting a detailed vignette about facial NMES including its risks. Results showed that LOTP was generally high and that participants remained more likely to participate than not to, despite a decrease in LOTP after the detailed vignette. LOTP was significantly predicted by participants’ previous knowledge about electrical stimulation and their tendency not to worry about the sensations of pain, and it was inversely related to concerns for burns and loss of muscle control. Fear of pain was also inversely related to LOTP, but its effect was mediated by the other concerns. We conclude that willingness to receive facial NMES is generally high across individuals in the studied age range (18–45) and that it is particularly important to reassure participants about facial NMES safety regarding burns and loss of muscle control. The findings are relevant for scholars considering using facial NMES in the laboratory.
... We individually viewed each student's circuit (virtually) to avoid errors in the set-up and the very real possibility of electrical shock if the circuit was not built and used correctly. [13][14][15][16] VIRTUAL LABS Students (n = 103) met weekly, for four hours, on Microsoft (MS) Teams, to work with their lab partner on four different cardiac labs: ...
... We have assumed that small voltages are not dangerous as long as the impedance to the body is high enough to prevent large currents, specifically currents less than 5 milliamps. [13][14][15][16] Wet skin could reduce the impedance such that a 9V battery combined with an improperly built circuit could cause a shock. Attaching the circuit to an electrical outlet, instead of just the battery, is not advised. ...
Hands-on labs are a critical component of biomedical engineering undergraduate education. Due to both the pandemic and the growing interest in online education, we developed a Do-it-yourself Electrocardiogram (DIY EKG) project. The Arduino-based DIY EKG kit instructed students how to build a circuit to obtain their own EKG and then analyze their EKG data using Matlab. Despite the obstacles of virtually trouble-shooting, 85.4% of students (n = 103) were able to obtain their own EKG at home. We have provided the labelled circuit drawings, step-by-step instructions, Matlab files, and results in this paper. Survey results indicate that 89% of students felt the DIY EKG project was a "challenging yet fulfilling experience."
Supplementary information:
The online version of this article contains supplementary material available 10.1007/s43683-021-00061-0.
... Variation of alternating current and human response over time [22] . ...
... However, the epidermis of human skin has rather large resistances, which adds the challenge in deciding sufficient voltage of the input signal for a painless desired stimulation. [18,19]. ...
Electrotactile Perception Threshold (EPT) is critical for designing electrotactile displays, which is the minimum amplitude of an electrical stimulus that can be perceived. A significant concern in electrotactile displays is skin irritation and burns due to prolonged electrical stimulus with high amplitude. This study aims to propose a method for reducing the EPT using a background stimulation with a vibrotactile display at subthreshold: 90% of the Vibration Perception Threshold (VPT) at 235 Hz. A psychophysical experiment was conducted to measure EPT at the middle of the left forearm with and without the vibrotactile display using the staircase method. A reduction of 3 to 5% in EPT was observed, which can be further enhanced with varying study parameters. In addition, the comfort and safety aspects of the user’s assessment have been analyzed. Electrotactile stimulations have a higher Steven’s power exponent (1.51). Hence a reduced threshold (although it’s only 3 to 5%) would be perceptually significant and advantageous for sensory substitution and rehabilitation (vision, auditory, and gustatory).
... However, the epidermis of human skin has rather large resistances, which adds the challenge in deciding sufficient voltage of the input signal for a painless desired stimulation. [18,19] A few challenges limit the widespread use of electrotactile displays. Varying the electrical impedance of the skin is a major challenge with electrotactile stimulation. ...
Electrotactile Perception Threshold (EPT) is critical for designing electrotactile displays , which is the minimum amplitude of an electrical stimulus that can be perceived. A significant concern in electrotactile displays is skin irritation and burns due to prolonged electrical stimulus with high amplitude. This study aims to propose a method for reducing the EPT using a background stimulation with a vibrotactile display at sub-threshold: 90% of the Vibration Perception Threshold (VPT) at 235 Hz. A psychophys-ical experiment was conducted to measure EPT at the middle of the left forearm with and without the vibrotactile display using the staircase method. A reduction of 3 to 5% in EPT was observed, which can be further enhanced with varying study parameters. In addition, the comfort and safety aspects of the user's assessment have been analyzed. Electrotactile stimulations have a higher Steven's power exponent (1.51). Hence a reduced threshold (although it's only 3 to 5 %) would be perceptually significant and advantageous for sensory substitution and rehabilitation (vision, auditory, and gustatory).
... Alternatively, electro-tactile (ET) devices are advantageous due to its small size, light weight, and high resolution (9)(10)(11)(12). Nevertheless, the human epidermis has rather large resistances, which makes it quite challenging to decide an appropriate voltage for creating desired stimulations without pain (13,14). It is possible to lower down voltage and current value for electrostimulation by using needle electrodes to release signal under the epidermis, but this kind of penetration mode still has the risk of skin lesions and infections (15)(16)(17)(18). ...
Tactile sensation plays important roles in virtual reality and augmented reality systems. Here, a self-powered, painless, and highly sensitive electro-tactile (ET) system for achieving virtual tactile experiences is proposed on the basis of triboelectric nanogenerator (TENG) and ET interface formed of ball-shaped electrode array. Electrostatic discharge triggered by TENG can induce notable ET stimulation, while controlled distance between the ET electrodes and human skin can regulate the induced discharge current. The ion bombardment technique has been used to enhance the electrification capability of triboelectric polymer. Accordingly, TENG with a contact area of 4 cm ² is capable of triggering discharge, leading to a compact system. In this skin-integrated ET interface, touching position and motion trace on the TENG surface can be precisely reproduced on skin. This TENG-based ET system can work for many fields, including virtual tactile displays, Braille instruction, intelligent protective suits, or even nerve stimulation.
... However, stimuli that cause subluxation of the hyoid bone have been noted to have the potential to cause aspiration [13]. Currently, safety guidelines for the use of electrical stimulation are being studied [14]. Aspiration, including aspiration pneumonia, is a serious or life-threatening risk. ...
Many activities can be carried out in virtual reality environments, and at present, reproducing the activity of eating or drinking is one developing field. Virtual eating or drinking can be divided into two types: those with food in the mouth and those without placing food in the mouth. Many studies have focused on changing the taste, size, and texture of food when eating or drinking, but few studies have focused on recreating the sensation of eating or drinking without actually placing food in the mouth. One of the challenges in virtually reproducing eating or drinking without the use of food or drink is how the sensation of swallowing is recreated in the esophagus. Herein we show Grutio, a device for recreating the sensation of swallowing by causing skin deformations that are the same as those during actual swallowing. When participants were asked to compare the sensation of drinking water with the recreated sensation, 66% of the participants had a stable pattern of swallowing sensations over the three-day experiment. participants who did not have a stable pattern also felt swallowing at least three times, and all participants were able to feel swallowing. The hardness and viscosity of the virtual swallowed food could be changed by adjusting the rate of skin deformation. The system allowed most users to virtually feel the sensation of swallowing through calibration. Although there were individual differences, the results of this study suggest that applying skin deformations externally to the neck can reproduce swallowing sensations internally.
... With soft materials, researchers have accommodated requirements of high flexi bility, low-profile, and comfort [34]. Still, it is challenging to employ these devices for general user interaction purposes because of a safety concern resulted from high operating volt ages (>1 kV) [33]. In this work, we chose PVDF ferroelectric polymer materials as core functional component which are mechanically soft and requiring relatively low driving voltage comparing to other soft actuators [47]. ...
We present HapSense, a single-volume soft haptic I/O device with uninterrupted dual functionalities of force sensing and vibrotactile actuation. To achieve both input and output functionalities, we employ a ferroelectric electroactive polymer as core functional material with a multilayer structure design. We introduce a haptic I/O hardware that supports tunable high driving voltage waveform for vibrotactile actuation while insitu sensing a change in capacitance from contact force. With mechanically soft nature of fabricated structure, HapSense can be embedded onto various object surfaces including but not limited to furniture, garments, and the human body. Through a series of experiments and evaluations, we characterized physical properties of HapSense and validated the feasibility of using soft haptic I/O with real users. We demonstrated a variety of interaction scenarios using HapSense.
