The purpose of this study was to clarify the stiffness of the anterior tibial muscle in the stance and swing phases during walking. Electrical stimulation was applied to the common peroneal nerve once every two steps at heel strike, and in the stance and swing phases. Mechanomyograms (MMGs) of the anterior tibial muscle were measured with an acceleration sensor. The measured MMGs were divided into stimulated and non-stimulated MMGs, and each set of MMGs was synchronously averaged. A Kalman filter was constructed by approximating the non-stimulated MMG with an autoregressive model. The stimulated MMG was smoothed with the Kalman filter, and then the walking acceleration was obtained. Evoked MMG was extracted by subtracting the walking acceleration from the stimulated MMG. The transfer function from electrical stimulation to evoked MMG was identified using a singular value decomposition method. The natural frequency as an index of muscle stiffness was calculated from the poles of the transfer function. The natural frequency of the evoked MMG during rest was also calculated. The evoked MMGs at heel strike, stance, and swing phases and during rest were approximated well with the sixth-, sixth-, eighth-, and sixth-order models, respectively. The higher order model in the swing phase may reflect the complex vibrations involving the foot and tendons. The natural frequency was highest at heel strike, followed by the stance phase, swing phase, and at rest. Stiffness of the anterior tibial muscle at the stance and swing phases in walking was clarified by the proposed method.

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We investigated the effects of two prominent aromas, lavender and jasmine, on peripheral and cardiac autonomic nervous system activity under stressful conditions, in a highly reproducible manner using an olfactometer. The subjects comprised 17 healthy men aged 20–24 years. In this within-subjects study design, all subjects were required to perform a simple calculation task for 30 min to induce cognitive stress, and aroma from lavender or jasmine essential oil or a control stimulus was inhaled intermittently (first 20 s of each 1-min interval) to prevent olfactory fatigue. The control stimulus was provided by triethyl citrate, an odourless solvent. In addition to subjective psychological assessments using a visual analogue scale, the temperature at the tip of the nose and cardiac activity on electrocardiogram were recorded as indices of peripheral and cardiac autonomic nervous system activities, respectively. Significant decreases in nose tip temperature and high-frequency (HF) component of heart rate variability (HRV), and a significant increase in heart rate were observed under all three conditions. However, compared with the control condition, lavender inhalation induced significantly greater decreases in nose tip temperature (p < 0.01) and HF component of HRV (p < 0.01), which indicated greater enhancement of sympathetic nervous system activity and suppression of parasympathetic nervous system activity. On the other hand, lavender inhalation induced a positive mood, less subjective stress, and increased concentration during the task (p < 0.01). These contradictory results of enhanced physiological stress response and lower subjective stress induced by lavender inhalation under stressful conditions suggest that lavender aroma may have effects other than sedation. Further studies are necessary to further clarify these effects.

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In this study, balancing capability in the longitudinal direction during rising from the seated position in the elderly was evaluated. In particular, the influence of the rising speed at the moment of leaving the seat, referred to as “seat-off,” on balancing capability was examined, since it affects the occurrence of falls. Twenty-eight elderly individuals participated in the study. They were divided into two groups based on their past experience of falls: 19 in the stable rising group and 9 in the unstable rising group. Body movement and the corresponding ground reaction forces during rising motion were measured at two different speeds in each subject, using a motion capture system and a force plate, respectively. From the measurements, “seat-off parameters” that characterize the seat-off motion were obtained. Seat-off parameter values in the stable and unstable rising groups were distributed separately in the seat-off parameter space, forming two distinct clusters. The cluster for the unstable rising group could be further divided into two sub-clusters. The results imply two types of instability during rising from seated position: instability in the forward direction and instability in the backward direction.

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Endolymphatic hydrops is a disorder in which an excessive amount of endolymph fluid causes an increase in the pressure of the endolymphatic system of the inner ear. In cochlea, endolymphatic hydrops can cause stretching in the scala media, a tubular construction that, along with two other similar structures, the scala vestibuli and scala tympani, runs through the cochlea from the base to the top. Visualizing the enlargement of the scala media has traditionally been done by histological study of tissue sections, and the degree can be calculated by comparing the ratio of the area of the scala media to the combined total area of the three compartments. However, this requires the obtainment of tissue samples, and thus is not suited for in vivo measurements, and is a labor intensive process in general. Imaging modalities that have been used to measure endolymphatic hydrops include MRI, μMRI and μCT. Recently, optical coherence tomography (OCT) has been applied for visualizing cochlea of mice in vivo. However, just visually discriminating between healthy and afflicted cochlea, and judging the degree of affliction can be difficult. Thus, we aim to establish a new technique for estimating the degree of enlargement of the scala media. We measured two healthy and two diseased cochlea using conventional area calculation, as well as our method, and present results that show that our technique correlates with established standards for measuring the degree of endolymphatic hydrops in cochlea (R=0.977, p=0.5×10⁻⁷).

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The purpose of this study was to develop an automated method without user interaction for selecting the optimal data acquisition window in magnetic resonance coronary angiography (MRCA). The major problem in MRCA is the effective suppression of coronary motion resulting from respiration and cardiac contraction. To compensate for cardiac movement, data acquisition is generally limited to the period when the coronary artery is not moving, mainly during end-diastole, and is referred to as the cardiac rest period. Generally, the cardiac rest period is identified by the operator. Therefore, it is subjective and requires an experienced operator for accurate identification. As for the region of interest, the right coronary artery is known as an appropriate region for determining the cardiac rest period. Previous studies attempted to determine the position of coronary artery using template matching techniques or difference between the pixel intensities along frames of the cine images, but the detection accuracy of the cardiac rest period was not sufficiently high. In this study, we estimated the position of coronary artery using the mitral valve, tricuspid valve and the apex as known coordinates. Then, the position of the coronary artery was estimated with high accuracy using a template matching technique. In addition, we proposed a method to track the position of coronary artery in a cine image by updating the template to determine the cardiac rest period. As a result, automatic determination of the cardiac rest period was possible in 24 subjects.

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Scale parameters are used to combine two or more models in different scales into one integrative model. One of the crucial issues in the research field of biosimulation in hemodynamics is how to determine the scale parameters in comprehensive hemodynamic models comprising a cardiac cellular contraction model and a circulation model. In this report, we propose a method for determining the scale parameters using mathematical equations derived from the shape of the left ventricle (LV), which is assumed to be a hemisphere. In this method, we derived five equations with seven unknown scale parameters. By using measured values of hemodynamic parameters such as the end-systolic and end-diastolic pressures and LV volume, we successfully determined seven scale parameters to reproduce pathological data of progressive hypertension in Dahl salt-sensitive rats. From the results, we found that accompanying the progression of hypertension, the active contraction force at end-diastole first increase by 54%, followed by 93% increase of the passive elastic force. We also successfully reproduced normal human physiological hemodynamics.

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Alpha-band (8–13 Hz) rhythm during encoding of sequentially presenting memory items was recorded using a 76-channel magnetoencephalograph. In a memory task, seven images each with an arrow pointing up, down, left or right were presented sequentially. Thereafter, a recall number was presented. Each participant memorized the arrow directions in the order of presentation and recalled the direction of the arrow for the recall number, and responded by pressing a button. Each participant also took part in a control task, in which the participant looked at the same images as those in the memory task but pressed the button previously instructed. Ten right-handed male volunteers performed 280 epochs of the memory task and 120 epochs of control task. The amplitudes of alpha-band rhythm during presentation of midterm (3rd–5th) items were compared with those of beginning (1st and 2nd) items. Fifteen sensors showed significant differences (midterm > beginning) in the memory task (0.01 < p < 0.05 at 11 sensors, 0.001 < p < 0.01 at 4 sensors), while no sensors showed a significant increase in the control task. Using the statistical parametric mapping (SPM) method, the region of increase in alpha-band rhythm from beginning to midterm was estimated to be located in the visual cortex and around bilateral temporal gyri. Additionally, the increase in amplitude from beginning to midterm was significantly greater before a correct answer than before a wrong answer (0.01 < p < 0.05 at 7 sensors and p < 0.001 at 1 sensor). Previous works demonstrated that alpha-band rhythm is increased by active inhibition of visual inputs that are irrelevant to memory. The region of increase estimated to be in the visual cortex agrees with previous works. An interpretation of our results is that since irrelevant visual inputs are successfully inhibited before a correct answer, the amplitude of alpha-band rhythm increases more than that before a wrong answer. These results indicate the possibility that alpha-band amplitude during memory encoding can be used as an index of memory performance.

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In brain function measurements by near-infrared spectroscopy, improving the measurement accuracy and expanding the measurement region are important for analyzing brain functional connectivity. Furthermore, for improvement of measurement accuracy, it is necessary to detect a signal for correcting disturbances or changes in skin blood flow. We have proposed a multi-channel signal processing method for realization of disturbance cancelation. To implement the cancelation method in an equilateral triangular probe placement, it is necessary to irradiate from each vertex sequentially and detect the light at the other vertices and at the center of the triangle. Thus, we adopt a combination of the multiple pulse method and the digital encoding method. Computer simulations show that treating the digital code in a pseudo-analog manner is effective for reducing the external noise and preventing mistakes in the demodulation bits. The demodulation process is confirmed using a phantom experiment and is then applied to the cancelation method. Using the cancelation method, the influence of a near-surface absorber is reduced from 64% to 27%. Thus, the multi-channel signal processing that we developed for the cancelation method improves measurement accuracy without increasing the system size.

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By integrating locally operated, small surgical robots and devices, a surgeon can perform, robotically assisted laparoscopic surgery safely and accurately. However, no locally operated robotic forceps functioning as the third arm can provide the wide field of view and the large working area required for single-incision laparoscopic surgery (SILS). For SILS using a locally operated third arm, the pivot point should be placed far from the other three instruments inserted through the single port, and the pivot axes should be bending. Size reduction of the differential geared mechanism is difficult. Designing bending pivot axes for the flexible worm mechanism is also difficult. Bending pivot axes are also difficult to achieve in the crank-curved manipulator that we proposed previously as the second arm. The crank distance is short because of the high-step cylinders. The curved forceps have low accuracy because of rubber deformation. In the present study, we modified the crank-curved manipulator and designed a new manipulator for use as the third arm in a sterile environment, which provides offset distance using low-step cylinders in the pivot point placed far from the other instruments, as well as bending forceps mechanisms using ball joints in the bending pivot axes. We succeeded to develop a bending forceps manipulator with offset distance as a locally operated, end-effector manipulator (offset LODEM) for use as the third arm. The operating range was 60 mm for the offset, 32° for the pitch and yaw axes, and 24 mm for the insertion/extraction axis. Positional accuracy was evaluated while performing a simulated surgical procedure. The accuracy was 0.5 mm, which is sufficient for handling organs. The manipulator successfully handled the target in the simulated surgical procedures to provide a wide field of view and a large working area. The offset LODEM was designed to allow minimally invasive, robotically assisted surgery performed by a doctor working near the patient. This device may be used for such applications.

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Moving-mask lithography with backside exposure was utilized to generate master male mold for biodegradable polymer microneedle production. The microneedle shape was calculated from the exposure dose, mask geometry, and moving trajectory using a newly developed computer simulation. Two conditions (90 µm aperture with 80 µm diameter of circular movement, and 90 µm aperture with 90 µm diameter of circular movement) were selected to evaluate the moving-mask exposure effectiveness. By changing the moving trajectory, two different sizes of microneedles were obtained from a single-size aperture mask. The fabricated microneedle and calculated microneedle geometry showed good qualitative agreement. The geometrical difference was 2% in basal diameter and 8%–16% in height. Using the master male mold, biodegradable polymer microneedles made of chondroitin sulfate C sodium salt (CSC) were fabricated by casting from a poly-dimethylsiloxane female mold. The shape of the biodegradable CSC microneedles showed good agreement with the master male mold.

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In recent years, surgeries requiring high surgical skills – including laparoscopic surgery and function-preserving surgery – are being more commonly conducted, which has led to the growing importance of surgeons’ training and preoperative simulations. Although various surgical simulators and 3D models of organs are now available, many surgeons still regard them as ineffective because they do not give a realistic sense of touch. In order to improve the quality of these simulations, it is necessary to collect data on how the shape of an organ is changed when pressed by laparoscopic forceps with various levels of force in actual operations. However, we have neither such data nor any equipment that can help us collect the data under operative environment. The main focus of this paper is to report on our development of the Pressure Measuring Grasper (hereinafter, PMEG) that can accurately measure the sizes of organs or tissues when they are grasped or pressed. PMEG is a modification of the digital vernier calipers, with the jaws modified to include our original parts (small load cells), making it possible to measure grasping pressure. The cross-sectional configuration of the PMEG jaws has the same structure as the tip of laparoscopic forceps, which allows the PMEG to simulate a situation in which tissue is grasped by laparoscopic forceps. We conducted two validation experiments to evaluate the measuring function of PMEG. One is verification of measuring pressure using weights, and the other is verification of measuring stiffness using a coil spring with known stiffness. These experiments showed that PMEG was able to measure the pressure and stiffness precisely. We also successfully used PMEG in a living pig’s body, and expressed in numerical data the relationship between the surgeon’s pressing force and organ deformation. The PMEG will contribute to the improvement of the surgical training system.

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Sweating, the intermittent secretion of fluid from the sweat glands, is an indispensable mechanism for the regulation of body temperature. The methods used to measure the sweat rate include an iodine starch test, a weight assay, and an ion electric conductivity method. The ventilation capsule method is another method for quantification of sweat rate. However, this method has a problem in that the subject’s physical activity is restricted by the firmly attached measurement probes. SNT-200, a wearable sweat meter developed by Rousette Strategy Inc., is already commercially available. This sweat meter contains silica gel that serves as an absorbent for sudoriferous steam and uses a temperature–humidity sensor to detect humidity changes in the device caused by sweating. However, the accuracy of the measurement has not yet been sufficiently investigated. This study was designed to provide evidence to validate the underlying measurement principle and accuracy of the device. We simulated various sweating conditions and performed simulated sweating measurements using SNT-200. In the first experiment, continuous sweating over a wide body surface was simulated. The calculated absorbed steam volume was 1.84 times greater than the real transpiration rate. In the second experiment, sweating was simulated in the form of water drops, and the sweat meter absorbed the generated steam. In the second experiment, the data obtained using SNT-200 was in good accord with the volume dispensed by a micropipette. These experiments provided convincing evidence that the total area of four steam holes (A1, in the equation for calculating the sweat rate) required correction. We therefore modeled the effective absorption area of the sweat meter as one circle encompassing the four holes (8 mm in diameter; 52 mm²) instead of a summation of the areas of four steam holes. Defining the effective absorption area by this method modified the value calculated in the first experiment, which agreed with the transpiration rate. In addition, the modified moisture absorption volume in the sweat meter converged within ± 20% error of the actual measurement, except at 30℃.

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A simple time-lapse cinematography (TLC) device was developed to enable detection, at the cleavage stages, of embryos that have the potential to develop into high-scoring blastocysts. The TLC device, which consists of an optical microscope system, an illumination system, a PC-controlled camera, and a focus adjustment unit, is encapsulated in a waterproof container to allow operation in a gas-controlled water jacket incubator. Operation of the device in a high humidity environment was ensured by an environmental test in an incubator. By capturing the images of bovine embryos every 10 min for several days, their growing process was precisely recorded. The feature quantities calculated from the temporal difference images were utilized to predict the cleavage timings of the embryos.

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To relieve or manage stress, objective assessment of stress is required. Instead of direct assessment of stress, we have been investigating whether responses to emotional stimuli are modulated by stress. As emotional stimuli, 8 pleasant (P: high arousal and high emotional valence), 8 neutral (N: low arousal and moderate emotional valence), and 8 unpleasant (U: high arousal and low emotional valence) pictures were selected from the International Affective Picture System (Univ. of Florida) database and presented to 20 healthy volunteers for 3 s per picture. Psychological scores using a visual analog scale (VAS) indicate that the emotional valence of the selected pictures was perceived by the participants as expected. Magnetoencephalograms (MEG) and traditional physiological markers of heart rate and oxygen saturation of the peripheral artery (SpO₂) were recorded simultaneously. Amplitude modulations of alpha rhythm (8–13 Hz) by presentation of emotional pictures were compared in a normal (control) condition and in a fasting-induced stress condition. Data for 17 participants were analyzed by two-way [emotional category (P/N/U) × condition (control/fasting)] repeated measures ANOVA and a multiple comparison test with Bonferroni's correction. Significant interaction in amplitude modulation was observed in the early stage (within 0.5–1.75 s from the start of picture presentation; p = 0.019). In the control condition, alpha rhythms were more significantly suppressed by both pleasant and unpleasant pictures than by neutral pictures (P < N: p = 0.011, U < N: p = 0.044). In the fasting condition, alpha rhythm was more significantly suppressed by unpleasant pictures than by pleasant pictures (U < P: p = 0.018). In other words, the amplitude depends on arousal in the control condition, while it depends on emotional valence in the fasting condition. Since it is known that alpha rhythm is suppressed by attention to visual input, these results suggest that attention to pleasant stimuli is lost under fasting-induced stress. On the other hand, heart rate and SpO₂ were not different between the emotional categories and were not modulated by the fasting-induced stress. MEG seems to be practical and powerful for objective detection of prompt response to emotion and assessment of stress, probably because of its high temporal resolution and selectivity to a specific brain region.

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Ventricular activation time (AT [ms]) is the time required to activate the ventricle electrically. The influences of AT on hemodynamics are of interest in clinical studies on methods for improving left ventricle (LV) function. However, the cardiovascular system is a dynamic system, in which many parameters are interrelated with each other, and teasing out the causality of the effects of AT within the system experimentally is difficult. In this research, we focused on analyzing the effects of changing AT on hemodynamics using a hemodynamic model by incorporating a cardiac tissue model into an LV geometric model within a circulation model. The cardiac tissue model is constructed by connecting 10 cardiac cellular contraction models in the fiber direction. In our cardiac tissue model, AT is represented by adding a constant delay time, δ_delay [ms], to the starting times of calcium transients between adjacent contraction models. Thus, AT becomes δ_delay × 9 [ms]. Simulations were performed under two conditions: normal AT (99 [ms], physiological); and prolonged AT (207 [ms], pathological). AT prolongation caused slight decreases in stroke volume (SV [mL]) and ejection fraction (EF [%]) by 2.10% and 6.00%, respectively, since both LV end-systolic and LV end-diastolic volumes increased by similar amounts. Maximum elastance (E_max [mmHg/mL]) decreased by 15.4%. The maximum rate of LV pressure rise (max dp/dt [mmHg/ms]) decreased markedly by 43.7% at longer AT. The cellular mechanisms underlying changes in half sarcomere length were analyzed individually in 10 cells. Even though hemodynamic parameters did not change significantly, we concluded that large differences in cell behaviors existed.

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Good mass transfer and high cell density culture are required for bioreactors using animal cells. These criteria can be met by fabricating a tissue in the bioreactor. In the present study, polypod particles were prepared using agarose, carrageenan, calcium alginate, and hydroxyapatite. The particles were then packed into reactors, and the reactors were filled with enzymatically cross-linked gelatin. Reactors with flow channels were then obtained upon dissolution of the gel particles. Cell adhesion, growth, and expression of organ (liver) function in the reactor were subsequently examined. Experiment using CHO-K1 cells suggested that the cells adhered and grew on the internal surface of the flow channels. HepG2 cells inoculated into the reactor expressed liver-specific functions over the 3-day culture period examined. Thus, the current findings demonstrate that the method developed can be applied to fabricate bioreactors to provide physiologically active substances and medical treatments for tissue engineering. Furthermore, this method was extended to the preparation of a hydroxyapatite-packed reactor by combining calcium alginate gel particles and hydroxyapatite. Therefore, this technique is expected to be applicable to both soft tissue models and hard tissue models such as bone.

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Melanoma is a malignant tumor occurring typically in the skin. Advanced melanoma has very poor prognosis, and is also called the “king of cancer”. On the other hand, early-stage melanomas are known to be cured completely by relatively simple treatments. Therefore, early detection and treatment of melanomas is very important. However, many melanomas are still diagnosed by subjective evaluation of a physician, in other words, visual inspection. Recently, the demands for development of quantitative melanoma diagnostic technology are increasing. Much research on melanoma diagnosis has progressed in response to these demands. This review introduces some recent advances in melanoma diagnosis using spectral imaging techniques, impedance measurement and diagnostic image analysis, and also briefly describes a novel biological agent against melanoma developed in Japan. A high-quality system using multispectral imaging technique has attracted attention, but the low specificity has been regarded as a problem. It should be noted that descriptions of medical contents are limited because this review is written for engineers and researchers.

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The dialysis fluid flow and solute removal performance of newly developed dialyzers and a downsized dialyzer were evaluated using a dimensionless correlation equation related to the mass transfer coefficient of the dialysate-side film in a mass transfer model, which was used in quantitative analyses in our previous study. The solute removal performance is greatly dependent on the dialysis fluid flow for low molecular weight solutes. Hence, the recently developed dialyzers are based on new design concepts incorporating jackets or hollow fibers that provide an evenly distributed flow. The new dialyzers tested were APS-15SA, PES-15Sαeco, PN-140S, and NV-15U. APS-15DSplus was used as a downsized version of the APS-15SA. The dialysate-side equivalent diameter d_e is smaller in the APS-15DSplus than in the APS-15SA, while the other design specifications are identical for these two devices. We measured vitamin B₁₂ clearance with the dialyzers operated at a blood-side flow rate Q_B = 200 mL/min, dialysate-side flow rates Q_D = 300–700 mL/min, and a net filtration rate Q_F = 0 mL/min. We then calculated the overall mass transfer coefficient. Using this value, we derived the dimensionless correlation of the Sherwood number (Sh), which includes the dialysate-side film mass transfer coefficient (k_D) and Reynolds number (Re_D). The exponent of Re_D was approximately 0.5 for all the dialyzers. The newly developed dialyzers have various design features for improving dialysis fluid flow. Unlike previous devices, the various new designs result in a convergence of performance. A comparison of APS-15SA and the downsized APS-15DSplus showed similar dependence of k_D on Re_D. This finding is novel and is attributed to the similarity in the relationship between dialysate-side fluid flow and dialysate-side film mass transfer in the two devices. In both dialyzers, the jacket has a full baffle and short taper structure, and the wave design of the hollow fiber membranes is identical. However, d_e was smaller in APS-15DSplus. Thus, analogous design concept employing the dimensionless correlation can be adopted for downsizing a device.

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An increasing number of closed-loop blood glucose (BG) control algorithms have been developed in recent years with the ‘artificial pancreas’ as the ultimate goal, although tight postprandial BG control remains an elusive goal. In this report, the authors propose a novel semi closed-loop BG control algorithm with meal announcement, which involves computation of the optimal continuous subcutaneous insulin infusion for a specific meal 60 min prior to mealtime. It utilizes a mathematical model of glucose-insulin metabolism to predict the impact of carbohydrates on postprandial BG levels based on carbohydrate intake and glycemic index (GI) value. The optimal pre-meal insulin is infused until mealtime, after which the control algorithm switches to model predictive control (MPC) to stabilize postprandial glycemia at the target value of 100 mg/dL (5.55 mmol/L). In silico results for four representative foods with GI values spanning a wide range show that in the case of exact patient-model match with precise information of carbohydrate composition and mealtime, postprandial BG levels can be maintained between 86–134 mg/dL (4.78–7.44 mmol/L) and 86–152 mg/dL (4.78–8.44 mmol/L) for 50 g and 100 g of carbohydrates, respectively. With consideration of intra-patient variability and meal-related uncertainties regarding the estimated carbohydrate amount and start of meal consumption, the BG control range is 75–159 mg/dL (4.17–8.83 mmol/L) with no critical hypoglycemic episodes.

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The dynamics of dehydroepiandrosterone (DHEA) and cortisol secretion from sleep through awakening were examined by collecting and analyzing saliva samples using a novel method. Sixteen male university students who voluntarily participated in this study were instructed to sleep from 0000 h to 0600 h, and their salivary cortisol and DHEA concentrations were evaluated during sleep until 1 h after awakening. We observed a marked elevation in DHEA upon awakening, referred to as the DHEA awakening response (DAR), which peaked at a different time from that of cortisol awakening response (CAR). Furthermore, DAR correlated positively with the subject's subjective quality of sleep, whereas cortisol concentration did not. Therefore, the DAR may be an index of subjective sleep quality.

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Implantable neural stimulators have recently attracted attention because of their potential applicability to the treatment of sensory neural disorders such as hereditary hearing loss and retinitis pigmentosa. However, the requirements for stimulation electrodes tend to be contradictory in some applications that require transmission of complex information to the nervous system, such as cochlear implants and retinal prostheses. They have to be sufficiently small to realize fine interfacing with the nervous system while remaining sufficiently large to inject enough charge to stimulate neurons without causing an irreversible electrochemical reaction. One solution to these requirements is to employ three-dimensional (3D) instead of planar electrodes. However, in conventional photolithography, the available material and size for fabricating electrodes are greatly limited. To overcome these limitations, we propose a novel fabrication process for stimulation electrodes, using mechanical micromachining. Using 3D bullet-shaped electrode increased the surface area by 3.6 times compared to conventional planar electrode with the same diameter. The proposed electrode, which was developed for retinal prostheses, showed sufficient charge injection capacity (CIC) to evoke light perception (phosphene) for blind patients. Furthermore, the CIC and electrode surface morphology remained stable during a six-month period of current pulsing in phosphate-buffered saline, which suggests suitability for chronic neural stimulation. The cause of the variance in the measured CIC and future applications of the proposed 3D electrodes were also considered.

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Spatial control of cell position is essential for numerous studies in tissue engineering, such as generation of linearly patterned muscle tissues, radially patterned liver lobule tissues, and circularly formed anal sphincter. This study proposes a novel method capable of patterning cells in a certain shape on a cell cultivation substrate. The concept is to pattern cells along the nodal position of resonance vibration on a cell cultivation substrate. Note that there are numerous resonance vibrations with different nodal patterns. In this study, we constructed a cell cultivation device consisting of a metallic cell cultivation substrate that can be excited to generate resonance vibration using a piezoelectric ceramic disk glued to the back of the substrate. In this study, we generated resonance vibration with a cross-circle nodal pattern. The cultivation substrate was a ø40 mm × 1 mm stainless steel plate, and the resonance frequency of the vibration was 21.4 kHz. Using the device, we conducted cell patterning experiments employing calf chondrocytes using various vibration amplitudes (1.0, 1.5, and 2.0 µm_p-p). Cells were cultured for 2 hours. After the experiment, the cell density distribution on the substrate was measured by staining viable cells with calcein. Additionally, we confirmed the viability of the patterned cells after exposure to acoustic pressure produced by the resonance vibration by counting the number of cells attached to the substrate. Viable cells were successfully patterned along the nodal position when the vibration amplitude was 1.5 µm_p-p. The number of cells attached to the substrate was 99.2% of that without vibration. Conversely, when the amplitude was 1.0 µm_p-p, the cells were not patterned. The acoustic pressure produced by 1.0-µm_p-p vibration was not large enough to move cells. Similarly, the cells could not be patterned when the amplitude was 2.0 µm_p-p. In this case, flow of the culture medium induced by the high acoustic pressure probably prevented the cells from patterning. In conclusion, cells can be patterned along the nodal position of resonance vibration generated with an appropriate vibration amplitude. We believe that this method has great potential for use in tissue engineering.

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