There exists a growing need for a cost-effective, reliable, and portable pulsation simulator that can generate a wide variety of pulses depending on age and cardiovascular disease. For constructing compact pulsation simulator, this study proposes to use a pneumatic actuator based on cam-follower mechanism controlled by a DC motor. The simulator is intended to generate pulse waveforms for a range of pulse pressures and heart beats that are realistic to human blood pulsations. This study first performed in vivo testing of a healthy young man to collect his pulse waveforms using a robotic tonometry system (RTS). Based on the collected data a representative human radial pulse waveform is obtained by conducting a mathematical analysis. This standard pulse waveform is then used to design the cam profile. Upon fabrication of the cam, the pulsatile simulator, consisting of the pulse pressure generating component, pressure and heart rate adjusting units, and the real-time pulse display, is constructed. Using the RTS, a series of testing was performed on the prototype to collect its pulse waveforms by varying the pressure levels and heart rates. Followed by the testing, the pulse waveforms generated by the prototype are compared with the representative, in vivo, pulse waveform. The radial Augmentation Index analysis results show that the percent error between the simulator data and human pulse profiles is sufficiently small, indicating that the first two peak pressures agree well. Moreover, the phase analysis results show that the phase delay errors between the pulse waveforms of the prototype and the representative waveform are adequately small, confirming that the prototype simulator is capable of simulating realistic human pulse waveforms. This study demonstrated that a very accurate radial pressure waveform can be reproduced using the cam-based simulator. It can be concluded that the same testing and design methods can be used to generate pulse waveforms for other age groups or any target pulse waveforms. Such a simulator can make a contribution to the research efforts, such as development of wearable pressure sensors, standardization of pulse diagnosis in oriental medicine, and training medical professionals for pulse diagnosis techniques.

Realistic haptic feedback is needed to provide information to users of numerous technologies, such as virtual reality, mobile devices, and robotics. For a device to convey realistic haptic feedback, two touch sensations must be present: tactile feedback and kinesthetic feedback. Although many devices today convey tactile feedback through vibrations, most neglect to incorporate kinesthetic feedback. To address this issue, this study investigates a haptic device with the aim of conveying both kinesthetic and vibrotactile information to users. A prototype based on electrorheological fluids was designed and fabricated. By controlling the electrorheological fluid flow via applied electric fields, the device can generate a range of haptic sensations. The design centered on an elastic membrane that acts as the actuator’s contact surface. Moreover, the control electronics and structural components were integrated into a compact printed circuit board, resulting in a slim device suitable for mobile applications. The device was tested using a dynamic mechanical analyzer to evaluate its performance. The device design was supported with mathematical modeling and was in agreement with experimental results. According to the just-noticeable difference analysis, this range is sufficient to transmit distinct kinesthetic and vibrotactile sensations to users, indicating that the electrorheological fluid–based actuator is capable of conveying haptic feedback.

Robust haptic devices that can convey the entire spectrum of human touch perception are necessary to afford realistic haptic experiences. For vivid and immersive interaction, a combination of both tactile and kinesthetic information must be presented to users. While vibrotactile feedback has become ubiquitous in today’s handheld devices, traditional kinesthetic actuators present significant challenges to miniaturization. Moreover, only limited success has been achieved in developing haptic actuators capable of conveying both tactile and kinesthetic sensations for small consumer electronics. Therefore, this study presents a compact actuator based on electrorheological (ER) fluid for generating a wide range of concurrent kinesthetic and tactile feedback. The design focus for the proposed actuator is to activate multiple operating modes of ER fluid to maximize the force generated by the actuator within a given small size constraint. To this end, the design incorporated two ground electrodes (a stationary ring electrode and a movable electrode attached to a spring element) for tuning the fluid’s yield stress in both flow and squeeze modes. After fabricating a prototype actuator, testing was performed with a dynamic mechanical analyzer (DMA) and an accelerometer to evaluate its ability to produce a wide range of kinesthetic feedback, as well as distinct vibrotactile feedback up to the limit of human perception. The results of kinesthetic testing indicate that the actuator can generate large forces (6.2 N maximum at 4 kV) at rates greater than the just-noticeable difference, indicating that the actuator can convey a wide range of kinesthetic sensations. Tactile evaluation using DMA and the processed acceleration response demonstrated that the actuator can generate both low and high frequency (up to 300 Hz) vibrotactile sensations at perceivably high intensity.

Generating haptic sensations in large touch displays is highly desirable, yet producing them for such application is challenging with conventional haptic actuators used in hand-held devices. This study proposes an electrostatic actuator utilizing frequency beating phenomenon with the goals of generating haptic sensations for large touch sensitive displays (TSDs). Unlike typical electrostatic actuators, the proposed haptic actuator incorporates two high-volt electrodes and a spring supported disk (moveable grounded mass) to enhance the intensity and pattern of haptic sensations. After fabricating a proof-of-concept prototype, its performance was experimentally evaluated by varying the beat frequency and the carrier frequency. Using mock-up LCD panels, a feasibility of the proposed actuator was evaluated for generating meaningful haptic sensations in large TSDs. Testing results show that the prototype generated a variety of unique vibration patterns at varying intensities based on combinations of the two input voltage signals. The results further show that the proposed actuator can produce sufficiently strong vibrotactile feedbacks in mock-up panels, indicating that the proposed electrostatic actuators can be a viable option for providing haptic sensations in large TSDs.

Accurate, non-invasive measurements of blood pressure and its continuous monitoring are extremely important for personal health care. Arterial tonometry, a method that is used to provide a detailed image of a patient's cardiovascular health, shows promise for being a non-invasive alternative to current blood pressure measurement methods. However, its measurement accuracy is sensitive to patient variations such as the stiffness of the skin. Thus, this project intends to investigate the effect of skin properties (i.e., stiffness) on the accuracy of tonometric blood pressure measurements. To this end, a test platform, consisting of a pulsatile system and a tunable skin stiffness apparatus (or MR apparatus), is constructed. The cam-follower pulsatile system built based on in vivo testing of human pulses is used to generate realistic pulse waveforms. The MR apparatus is able to adjust its stiffness using Magneto-Rheological (MR) fluid whose apparent viscosity changes with applied magnetic fields. Placed at the surface of the MR apparatus, a cylinder with a frictionless plunger simulates a variable applanation force or “hold-down pressure” of tonometry by adjusting the added weights atop the cylinder. Using this test setup, a series of tests were performed by varying the input magnetic field and the weights, which effectively adjusts the skin stiffness and the hold-down pressure, respectively. The vertical displacement of the plunger caused by the internal pulse pressure was measured using a laser displacement sensor. The output displacement waveforms were analyzed with the focus on the peak amplitude difference of the waveforms, which is related to the augmentation index (a surrogate measure of arterial stiffness). The results show that there exists an “optimal” plunger weight or “hold-down pressure” that provides the most distinct output pulse waveforms. The results further show that the difference in the first two peak values decreases as the skin stiffness increases, indicating that the stiffer the skin property, the less the “hold-down pressure” effects on the accuracy of the tonometry measurements.

Radial artery pulse waveforms (RAPWs) have been actively studied for decades because they provide critical health information, particularly related to risk factors of cardiovascular disease. The primary goal of this study is to develop a novel mathematical model that can regenerate age-dependent RAPWs by decomposing a single pulse pressure waveform (PPW). This study proposes to decompose a PPW into three waveform components with one forward wave component and two reflected wave components based on the physiology of pulse waveforms. Treated as basis functions, the three components with associated control parameters are incorporated in the proposed mathematical model. The underlying idea of the model is to generate desired pulse waveforms by combining basis functions whose characteristics depend on selection of control parameter values. For the current study, after determining the nine control parameters of the basis functions by post-processing algorithms, the proposed model for the PPW is derived from a linear combination of the basis functions. Using the model along with in vivo RAPW data, this study evaluates the performance of the model in regenerating PPWs for a wide range of ages from 85 years old to 15 years old. The results show an error of less than 6% between the PPWs numerically derived from the model and the in vivo data for the two key matrixes used in this study (the least-square error norm and the radial augmentation index), validating the effectiveness of the model. The model is applicable for RAPW simulator analysis and development.