Self-rechargeable cardiac pacemaker system with triboelectric nanogenerators.

Self-powered implantable devices have the potential to extend device operation time inside the body and reduce the necessity for high-risk repeated surgery. Without the technological innovation of in vivo energy harvesters driven by biomechanical energy, energy harvesters are insufficient and inconvenient to power titanium-packaged implantable medical devices. Here, we report on a commercial coin battery-sized high-performance inertia-driven triboelectric nanogenerator (I-TENG) based on body motion and gravity. We demonstrate that the enclosed five-stacked I-TENG converts mechanical energy into electricity at 4.9 µW/cm3 (root-mean-square output). In a preclinical test, we show that the device successfully harvests energy using real-time output voltage data monitored via Bluetooth and demonstrate the ability to charge a lithium-ion battery. Furthermore, we successfully integrate a cardiac pacemaker with the I-TENG, and confirm the ventricle pacing and sensing operation mode of the self-rechargeable cardiac pacemaker system. This proof-of-concept device may lead to the development of new self-rechargeable implantable medical devices.

Design of a stimulation protocol to predict temperature distribution in subcutaneous tissue using the finite element model.

Moxibustion is a traditional Oriental medicine therapy that treats the symptoms of a disease with thermal stimulation. However, it is difficult to control the strength of the thermal or chemical stimulus generated by the various types and amounts of moxa and to prevent energy loss through the skin. To overcome these problems, we previously developed a method to efficiently provide RF thermal stimulation to subcutaneous tissue. In this paper, we propose a finite element model (FEM) to predict temperature distributions in subcutaneous tissue after radio-frequency thermal stimulation. To evaluate the performance of the developed FEM, temperature distributions were obtained from the FEM, and in vivo experiments were conducted using the RF stimulation system at subcutaneous tissue depths of 5 and 10 mm in the femoral region of a rabbit model. High correlation coefficients between simulated and actual temperature distributions-0.98 at 5 mm and 0.99 at 10 mm-were obtained, despite some slight errors in the temperature distribution at each depth. These results demonstrate that the FEM described here can be used to determine thermal stimulation profiles produced by RF stimulation of subcutaneous tissue.

Development of a noncontact heart rate monitoring system for sedentary behavior based on an accelerometer attached to a chair.

Although people spend a third of their day engaged in sedentary activities, research on heart activity during sitting is almost nonexistent because of the discomfort experienced when electrocardiogram (ECG) measurement electrodes are attached to the body. Accordingly, in this study, a system was developed to monitor heart rate (HR) in a noncontact and unconstrained way while subjects were seated, by attaching an accelerometer on the backrest of a chair. Acceleration signals were obtained three times from 20 healthy adults, a detection algorithm was applied, and HR detection performance was evaluated by comparing the R-peak values from the ECG. The system had excellent performance results, with a sensitivity of 96.10% and a positive predictive value of 96.43%. In addition, the HR calculated by the new system developed in this study was compared with HR calculated using ECG. The new system exhibited excellent performance; its results were strongly correlated with that of ECG (r = 0.97, p [Formula: see text] 0.0001; average difference of -0.08  ±  4.60 [mean ± 1.96∙standard deviation] in Bland-Altman analysis). Accordingly, the method presented in this study is expected to be applicable for evaluating diverse autonomic nervous system components in a noncontact and unconstrained way using an accelerometer to monitor the HR of sedentary workers or adolescents.

A unique electrical thermal stimulation system comparable to moxibustion of subcutaneous tissue.

Moxibustion strengthens immunity and it is an effective treatment modality, but, depending on the material quantity, shape, and composition, the thermal strength and intensity can be difficult to control, which may cause pain or epidermal burns. To overcome these limitations, a heat stimulating system which is able to control the thermal intensity was developed. The temperature distributions on epidermis, at 5 mm and 10 mm of depth, in rabbit femoral tissue were compared between moxibustion and the electric thermal stimulation system. The stimulation system consists of a high radio frequency dielectric heating equipment (2 MHz frequency, maximum power 200 W), isolation probe, isolation plate, negative pressure generator, and a temperature assessment system. The temperature was modulated by controlling the stimulation pulse duty ratio, repetition number, and output. There were 95% and 91% temperature distribution correlations between moxibustion and the thermal stimulus at 5 mm and 10 mm of depth in tissue, respectively. Moreover, the epidermal temperature in thermal stimulation was lower than that in moxibustion. These results showed that heat loss by the electric thermal stimulation system is less than that by the traditional moxibustion method. Furthermore, the proposed electric thermal stimulation did not cause adverse effects, such as suppuration or blisters, and also provided subcutaneous stimulation comparable to moxibustion.

Electrical characterization of proposed transpositional acupoints on the urinary bladder meridian in a rat model.

Specific electrical characteristicsof acupointswere investigated on the urinary bladder (BL) meridian in 14 rats. BL acupointsand non-acupoints on the back were selected and their electrical voltages were measured by using aSPACsystem.The mean voltages of each point or each line were statistically analyzed by using the ANOVA test.The BL meridian showed voltages higher than those of the reference line (P < .05). Bilateral 1st BL lines presented higher voltages than bilateral 2nd BL lines (P < .05). Most BL acupoints had voltageshigher than those for the corresponding reference points (P < .05). In particular, theright BL16 exhibited the biggest difference from the reference point, followed by the left extra BL point-2, the right BL27, the left BL17, and theleft BL45. Additionally, the distributions of neurofilamentsfor several points were investigated by using immunohistochemistry. There was a trend for the BL acupoints to have larger numbers of neurofilaments than the reference points, and that trend seemed to be directly proportional to the difference in voltage between the points.In conclusion, BL acupoints on the back in ratsexhibited specific electric and histologic characteristics. Therefore, those acupointsmay be utilized to investigate the efficacy of acupuncturewith laboratory animals.

Repeatability of the accelerometric-based method to detect step events for hemiparetic stroke patients.

This study is to evaluate the repeatability of the accelerometric-method to detect step events for hemiparetic stroke patients. To evaluate this method, four adults with chronic hemiparetic stroke were participated. The repeatability of this method using a single three-axis accelerometer was evaluated with a six optical camera motion capture system. The correlation statistics and Bland-Altman plot were then used to evaluate the agreement between the step-time differences from the accelerometer data and the reflective markers data. The correlation coefficient of each two data was 0.99 (p < 0.001) and retest result was 0.99 (p < 0.001). The mean ± standard deviation (SD) between each two data along with the 95% limits of agreement (LOA = ± 1.96 SD) was 2.58 ± 2.37 ms (LOA = -2.07 ms and 7.23 ms), and retest result was 3.73 ± 2.02 ms (LOA = -0.22 ms and 7.68 ms). These results show that the suggested method is useful to detect step events for hemiparetic stroke patients.

A design of RF stimulator which is similar to temperature distribution by moxibustion (preliminary study).

We developed a novel radio-frequency (RF) stimulator to mimic heat effects similar to the temperature distributions created by moxibustion in porcine tissue. Moxibustion is a traditional Oriental medicine technique using moxa, which is utilized not only to cure disease, but also to increase immunity. However, it may lead to undesired effects including severe pains, blisters, and burns because of the difficulty of controlling heat intensity during the process. To overcome these problems, a novel RF stimulator that can conduct thermal energy to the deep tissue of the body and also easily control the power of heat stimulation was proposed. RF stimulating protocols were designed to mimic the temperature profiles of two types of moxibustion. In our results, the temperature distributions created by the proposed protocols were similar to those attained by moxibustion. It was also shown that the proposed protocols were more effective than moxibustion for transferring heat effects into deep tissues.

A new noise reduction method for oscillometric blood pressure measurement.

In this paper, a new noise reduction method was proposed for oscillometric blood pressure measurement. The proposed method uses a capacitive sensor and an adaptive filter to minimize blood pressure measurement error. Noise such as undesired external pressure applied to cuff was focused on. Three types of the distorted oscillation signals (no overlap, non-consecutive overlap, consecutive overlap between the noise and the oscillation) were used to compare the conventional method using linear interpolation and the proposed method using the adaptive filter. The proposed method outperformed the conventional method in the case of consecutive overlap between the noise and the oscillation. The proposed method could be useful for measuring blood pressure in such a noisy environment that the subject is being transported.

Development of acupoints discrimination system using electric properties of acupoints and non-acupoints.

The conventional acupuncture-point stimulus pattern uses direct current (DC) to discriminate acupuncture point and meridian lines, which are fundamental to diagnosis and treatment in Oriental medicine. However, DC is insufficiently reliable in discriminating these acupuncture points and lines. To overcome these problems, the authors extracted optimal parameters (e.g., square-like waveform with a frequency of 3 to approximately 5 kHz) with a single power alternating current (SPAC) stimulus pattern of 1.28V. The SPAC stimulus pattern has little or no effect on cells and the body's physiological state and minimizes polarization and ionization of cells because it uses low voltage and alternating current. The authors developed a new meridian discrimination system that can be used with the SPAC.

A new acupuncture point detection using the impedance measurement system based on ANF and phase-space-method.

In this study, a new method for acupuncture point detection using the impedance measurement system based on the PSM (Phase Space Method) is presented. The developed device has been developed as detectors for acupuncture points which are used for diagnosis and treatment in acupuncture. In this system, multi-frequency current injection and voltage measurements are both performed by the surface electrodes, which are controlled by a microcontroller. Also, the microcontroller process continuous time demodulation of the modulated signal by multi frequency components using the adaptive notch filter. After that, PSM is applied about each frequency using an acupuncture equivalent model which is proposed in the pre-study.