A Micro Electro-Mechanical System (MEMS) is a micro-sized mechatronic device based on semiconductor integrated-circuit manufacturing technology. MEMS technology is inherently a very powerful tool for researchers to manipulate and measure the microscopic biological components of biological tissues since their basic constituent units, cells and intracellular microstructures, are also micron or even submicron in size.

MEMS technology applied to medicine and life sciences is called Bio-MEMS. Many Bio-MEMS devices and technologies have been developed in recent years, including microfluidic devices for cell culture, manipulation, and measurement, as well as lab-on-a-chip devices for chemical reactions and analyses on MEMS devices.

This special issue consists of 13 papers: 1 review article, 1 letter, and 11 research papers. These papers include studies on mechanical stress on cells using MEMS devices, the control of cell functions through microfabrication techniques, cell measurement and in vivo microenvironment simulation using microfluidic devices, and basic research on wearable devices and self-assembling microstructures using MEMS technologies. The editorial committee members are confident that this special issue will make a significant contribution to the further development of Bio-MEMS.

We sincerely appreciate the excellent contributions of the authors and the time and effort of the reviewers. We would also like to thank the editorial board of the Journal of Robotics and Mechatronics for their support of this special issue.

In the present study, we describe attempts to develop medical/healthcare measurement devices from the body surface using microfabrication technology. These devices can be divided into two types: internal vessel diameter measurement from the body surface using ultrasound to measure blood pressure and vascular tone, and collection and measurement of biological substances and collection of cells from the body surface.

A wearable biosensor was specifically engineered to measure uric acid, a biomarker present at wound sites. This biosensor, fabricated as a disposable and wearable device, was seamlessly integrated onto a polyethylene terephthalate (PET) substrate by utilizing carbon and silver conductive paste as the electrodes. The enzyme uricase was immobilized onto the working electrode by utilizing chitosan, a biocompatible material, to create this biosensor. Notably, the uric acid biosensor fabricated with chitosan showcased exceptional performance metrics, including remarkable output current values and impeccable stability. These findings suggest the prospective utilization of chitosan-based uric acid biosensors for the accurate measurement of uric acid on human skin in future applications.

In orthodontics, various forms of mechanical stimulation induce opposing bone metabolism mechanisms. Bone resorption and bone formation occur in areas of compressive and tensile force action, respectively. The mechanism that causes such a difference in bone metabolism is still unclear. In this study, we investigated the difference in the osteoblastic calcium signaling response between compression and stretching mechanical stimuli. We applied two types of mechanical stimuli to osteoblast-like MC3T3-E1 cells: first microneedle direct indentation onto the cell as compression stimuli, and second stretching stimuli by using originally developed cell stretching MEMS device. Cells were treated with thapsigargin and calcium-free medium to investigate the source of the calcium ion. The results demonstrated variations in the osteoblastic calcium signaling response between the compression and stretching stimuli. The magnitude of an increase in the intracellular calcium ion concentration is much higher in the compression stimuli-applied cell group. Treatment of calcium-free medium nearly suppressed the calcium signaling response to both types of mechanical stimulation. Thapsigargin treatment induced an increase in the magnitude of calcium signaling response to the compression stimuli, while suppressed the slow and sustained increase in the calcium ion concentration in the stretching stimuli-applied cell group. These findings demonstrate the difference in the characteristics of osteoblastic calcium signaling response between compression and stretching mechanical stimuli.

Various devices have been developed that use stretching silicone sheets to evaluate cellular mechanotransduction. However, few studies have explored predefined cell alignments using mechanical stimuli for engineering applications, including cell sheets and drug screenings. Therefore, we proposed a magnetically driven cell-stretching device for predefined cell alignment in vitro, which consisted mainly of a circular silicone membrane with a neodymium magnet and standard cell culture dish. As the proposed device was incorporated into a cell culture dish, there may be a small risk of contamination in long-term incubation experiments. The device was fabricated by assembling a polydimethylsiloxane membrane and silicone ring. The fabricated device showed that the membrane strain increased with increasing voltage application to the electromagnet, and indicated that cell alignment occurs when strain exceeds 0.8%. Following cyclic stimulation of cells adhered to a membrane for 4 h in a CO₂ incubator with 1.05% strain at 0.1 Hz, cell alignment with the predefined direction increased by 20.4% compared to that before stimulation. The findings imply that the proposed device may be utilized for predefined cell alignment.

It is known that the cells responds to external mechanical stimulations. Although the effectiveness of vibrational stimulation for the osteoanagenesis has been reported, the clarification of detailed mechanism for this phenomenon is insufficient. In this study, a micro device has been developed to evaluate the cell dynamics and responses to vibrations. The micro device has an array of moving micro stages which have transparent 5 µm thick thin film to enable them to observe the cell responses to vibrational stimulations by using an optical microscope. The moving micro stages are moved with a needle actuated by piezo actuator. Microfabrication processes, such as conventional photolithography, lift-off, and sacrificial layer etching, were used to fabricate the micro device. We designed two types of concepts for supporting and vibrating moving micro stages. Prototypes were fabricated and evaluated under vibrational conditions. Proposed design with the moving micro stages vibrating perpendicular to the beams generated simple linear oscillation without rotation. It was verified that the fabricated micro stage could be vibrated at the acceleration amplitude of 0.1 and 0.2 G with frequency 15, 45, and 90 Hz.

DNA damage induced by the ultraviolet (UV) light, which affects adversely on genome stability, causes many kinds of diseases. Thus, a biochemical or biomechanical method in DNA damage protection is well required. In the present study, we investigated the effects of mechanical factors, such as deformation of cell nucleus using polydimethylsiloxane (PDMS)-based microfabricated array of micropillars, on UV radiation resistance of DNA in cultured cells. The epithelial-like cells spread normally in the spaces between micropillars and their nuclei showed remarkable deformation and appeared to be “trapped” mechanically on the array of pillars. We found that the UV radiation-induced DNA damage estimated by the fluorescent intensity of the phospho-histone γ-H2AX, was significantly inhibited with the nucleus deformation on the pillars. The result indicates that the inhibition of UV radiation-induced DNA damages might be resulted from structural change of DNA caused by the mechanical stress of the cell nucleus on the micropillars.

Vascular remodeling is a crucial process for the effective delivery of oxygen and nutrients to the entire body during vascular formation. However, detailed mechanisms underlying vascular remodeling are not yet fully understood owing to the absence of an appropriate experimental model. To address this, in this study, we utilized a microfluidic vascular model with perivascular cells to investigate the mechanism of vascular remodeling by culturing human umbilical vein endothelial cells (HUVECs) and mesenchymal stem cells (MSCs) in a microfluidic device. We compared two different cell culture conditions: culturing HUVECs and MSCs (1) separately in different channels and (2) in the same channel. In both conditions, microvascular networks covered with perivascular cells were formed. Interestingly, a significant inward vascular remodeling occurred over time when HUVECs and MSCs were cultured in different channels. This remodeling was mediated by direct endothelial–perivascular crosstalk through α₆ integrin. Furthermore, computational fluid analysis revealed that hypothetical shear stress on the luminal surface of microvessels was attenuated during inward vascular remodeling, suggesting that the remodeling might be an adaptive change. Our findings and the microfluidic model will be useful not only for further elucidation of mechanisms underlying physiological and pathological vascular remodeling but also for constructing functional vascularized tissues and organs by controlling vascular remodeling.

Single-cell screening, which has revolutionized the life sciences, is an important method for detecting, separating, or treating specific cells based on desired characteristics. Previously, single cells of interest were manually identified in an image, which required human labor and time. We developed an automated photopolymerization system to encapsulate suspended single cells in approximately 50-µm photo-crosslinkable hydrogel squares. An image was captured, and single cells were selected from grouped cells based on image processing. A generated image was transferred to a digital micromirror device (DMD), and in parallel, target-suspended single cells were encapsulated in gelatin methacryloyl (GelMA) hydrogels. We built a data transfer platform based on a Power Automate Desktop (PAD), completed the data transfer, and projected the processed image onto a sample in 10 s, ensuring a minimum alignment error of 6.2 µm.

Tissue formation from heterogeneous cell types, similar to those in vivo, is an important technique for development of new drugs and formation of artificial organs. In vivo tissues are complex arrangements of heterogeneous cells that interact with each other. To create such tissues in vitro, it is essential to develop a technique that arranges heterogeneous cells in an arbitrary configuration. Currently, we are developing a new gel patterning technique to create effective cell micropatterns by using photolithography and alginate gel, which inhibits cellular adhesion. In this study, we considered that a more flexible gel patterning technique was required for creating order-made formations of complex tissues. We created gel patterns by removing the alginate gel using laser processing, and cells were cultured on the formed patterns. Complex heterogeneous cell patterns were achieved by adjusting various technical parameters such as the laser power, spot diameter, and alginate gel film thickness. Based on our results, we anticipate that our technique will prove useful for the development of regenerative medicine and tissue engineering.

Microplastics (MPs) can adsorb heavy metals and metalloids and may cause a potential health hazard. Precise measurements of their size, shape, composition, and concentration at a single-MP level are important to evaluate their potential toxicity and identify their original source. However, current single-MP analytical methods such as micro-Raman spectroscopy and scanning electron microscopy have low throughput. Therefore, in this study, we applied the ion current sensing method, which has been used for single cell analysis, to single-MP analysis and examined whether size measurement and composition analysis of MPs at the single particle level are possible. In single-MP measurements, plastic particles must be mono-dispersed in solution at least within the measurement time. The agglomeration behavior was carefully observed after adding sodium dodecyl sulfate to tris-borate-EDTA buffer at 2–16 mM. Under these conditions, the size of polystyrene beads could be measured using the ion current sensing under the mono-dispersed condition. Next, ion current sensing was performed on four pseudo MPs fabricated from different materials (polyethylene, polyethylene terephthalate, polypropylene, and polyvinyl chloride) that were mechanically grazed and UV-irradiated to imitate real marine MPs. Although significant differences in the ion current signals from different material MPs were not observed, fast (100 MPs within 2 s) and precise measurements in the MPs’ sizes at a single-MP level were successfully achieved.

This study discusses component separation using a microfluidic device. Based on the separation principle, a method was adopted to generate an external force due to centrifugal force in a spirally designed channel. In this study, four types of polystyrene particles with different diameters ranging within 1–45 µm were used, and the separation performance was evaluated for each particle size. The centrifugal force increased as the flow velocity in the channel increased; however, this time, the test was conducted with the flow rate, which is an input parameter fixed at 100 µL/min. The results of the micro-channel observation using a high-speed camera indicated that the particle density might be a factor in the decrease in separation efficiency. Therefore, by conducting tests at three different particle densities, we were able to experimentally investigate the change in separation efficiency based on the particle size and density. In this study, we considered the separation efficiency due to the size and density of the particle diameter along with its application to an onsite-type separation device.

Liposome-based molecular robots that molecular systems are integrated into a giant liposome have been proposed; they are expected to be applied in the fields of medicine, environmental science, food science, and energy science. However, the performance of these molecular robotic components, including intelligence, sensors, and actuators, still hinders their practical use. In particular, the actuators used in the molecular robots, such as molecular motors, do not provide sufficient performance to move the giant liposomes. Hence, we propose an osmotic-engine-driven liposome and demonstrate the migration of liposomes in a microfluidic channel by applying a salt concentration difference between the front and rear of the liposome. Although the migration mechanism is simple and has the potential to provide sufficient mobility performance, control techniques for the movement speed and on/off switching are not established. Herein, we describe a speed control method of osmotic-engine-driven liposomes using pore-forming membrane proteins. In this study, we evaluated the effect of reconstituted α-hemolysin (αHL) nanopores on the water permeability through lipid bilayers. Thereafter, we demonstrated the change in displacement speeds of liposomes with and without nanopores. We expect the speed control method using nanopores to be applied to the liposome-based molecular robots.

In this study, we developed a system for selective self-assembly of millimeter-scale components differentiated by adhesive patterns. This was achieved by designing concentric circular patterns having different radii but the same total length of peripheries. Small polymer sheets having solder adhesive patterns in these designs were simply attached to the millimeter-scale components to be assembled in a stirring container. This strategy was effective in avoiding an overlap between different patterns and enforcing the selective bonds between identical patterns among three types of components. Finally, the selective assembly of a functional structure (i.e., poly(N-isopropylacrylamide) gel actuator) was demonstrated.

In this paper, we propose the design and implementation of spherical magnetic joint (SMJ)-based gait generation for the inverted locomotion of multi-legged robots. A spherical permanent magnet was selected to generate a consistent attractive force, enabling the robot to perform inverted locomotion under steel structures. Additionally, the robot’s foot tip was designed as a balljoint mechanism, providing flexibility in foot placement at any angle between the tip and surface. We also introduced an adjustable sleeve mechanism to detach the foot tip during locomotion by creating a fulcrum during the tilt and pull steps. This mechanism effectively reduced the reaction force based on the sleeve diameter. The experimental results showed a 46% decrease in the present load when using the adjustable sleeve mechanism compared to direct pulling. For inverted locomotion, a quadruped robot and a hexapod robot, which represent the predominant type of multi-legged robots, were constructed. We integrated the SMJ and adjustable sleeve into both robots, enabling them to perform inverted locomotion with various gaits such as crawling, trotting, square, and tripod gaits. Our analysis examined the characteristics of each gait in terms of velocity and stability, thereby confirming the versatility of the proposed SMJ, which can be applied to different types of legged robots.

A household disaster map is required as a countermeasure against earthquakes, particularly in crowded, cluttered indoor spaces where evacuation is difficult. Therefore, the visualization of areas that are likely to hamper evacuation is important. This study focused on cleaning robots, which generate environmental recognition maps to control their movement. We proposed a system that detects obstacles impeding evacuation for households using an environmental recognition map generated by a cleaning robot. The map generation algorithm was based on image processing and stochastic virtual pass analysis based on a pseudo cleaning-robot model. Image processing involving the binarization process was conducted to identify the interior and exterior areas of a room. Stochastic virtual pass analysis was performed to track the coordinates (i.e., virtual pass of the robot model) inside the room. Furthermore, the proposed system was tested in a laboratory, and the application of the changing-layout design simulation was considered.

Snow removal work using construction equipment faces problems such as a shortage of skilled operators owing to the declining birthrate and aging population, work in dangerous areas, and accidents caused by a lack of concentration during long work hours. To improve the working environment, research and development of automation of construction equipment are actively conducted. Therefore, in this study, we aim to generate a driving path for wheel loaders for snow removal work in a work environment surrounded by obstacles, such as walls and fences. Furthermore, the proposed method considers the changing shape of the snow piles during the removal. We experimentally verified that snow removal could be performed using an actual wheel loader on the route generated by the proposed simulation.

We conducted a study on the user experience design process ((i) research and analysis, (ii) concept design, and (iii) prototyping) to identify the requirements for a robot for supporting construction management. From this study, seven hypotheses were obtained for these requirements. One horizontal prototype satisfying three of these hypothesized requirements and three local prototypes satisfying one hypothesis each were created. The prototypes were evaluated in the field. The remaining one hypothesis was not tested at this time due to the longer trial period required for validation. It would be more appropriate to validate it during the evaluation of the vertical prototype or the system as a whole. Based on the results of the field evaluation, it was made clear that the hypothesized six requirements are reasonable requirements for a robot to support construction management.

Ultrasound (US) imaging is beneficial for kidney diagnosis; however, it involves sophisticated tasks that must be performed by physicians to obtain the target image. We propose a target-image search strategy combining visual servoing and deep learning-based image evaluation for robotic kidney US imaging. The search strategy is designed by mimicking physicians’ motion axis of the US probe. By controlling the position of the US probe along each of the motion axes while evaluating the obtained US images based on an anatomical feature extraction method via instance segmentation with YOLACT++, we are able to search for an optimal target image. The proposed approach was validated through phantom studies. The results showed that the proposed approach could find the target kidney images with error rates of 2.88±1.76 mm and 2.75±3.36°. Thus, the proposed method enables the accurate identification of the target image, which highlights its potential for application in autonomous kidney US imaging.

Quadruped mammals can control the movement of their center of gravity when turning by skillfully utilizing their bodies to achieve adaptive turning movements. Interestingly, the low-speed turning behavior also changes depending on the animal’s morphology. Therefore, this study aims to understand the control algorithm of low-speed turning, which can reproduce the turning behavior according to the location of the center of gravity. Specifically, we constructed a control algorithm based on the knowledge that animals steer with the leg closest to the center of gravity and verified it with a quadruped robot whose center of gravity could be adjusted. Consequently, the behavior observed in animals was successfully reproduced, with a stable and large turning angle per time when the proposed control algorithm was used.

We previously proposed on the underwater cable-driven parallel robot (UCDPR), a system comprising multiple surface robots, and designed a modeling and trajectory tracking control method for it. However, the conventional trajectory tracking control of the UCDPR using the kinematic controller faced several issues. These included challenges in control gain tuning due to model uncertainty and a decline in trajectory tracking performance caused by changes in system characteristics due to environmental factors like current velocity. In response, this study focuses on the development of an adaptive kinematic controller. The aim is to mitigate the effects of uncertainties and other factors while ensuring effective trajectory tracking. This is achieved by incorporating an adaptive modification term into the conventional kinematic controller, which can be tuned adaptively in real-time. To validate the effectiveness of the adaptive kinematic controller, we conducted numerical simulations using a planar 2-DOF UCDPR.

Haptics applications are receiving increasing attention in entertainment, medical support systems, and various industries. Three-dimensional (3D) haptics is important to provide users real experiences. Conventional haptic devices consist of many motors and mechanical elements grounded in an environment. Therefore, they are large in size and heavy. Haptic devices using asymmetric vibrations can display illusion forces with mobile structures. However, they need additional structures (comprising actuators) to generate a 3D illusion force; however, the operational mechanism becomes complex. To solve this problem, we propose the use of a 3-degree-of-freedom (3DOF) oscillatory actuator that can generate a 3DOF vibration using only one actuator. This study describes the basic characteristics and operating verification of the 3DOF oscillatory actuator. The static thrust characteristics are quantified and analyzed using a finite element method. The dynamics are calculated based on numerical simulations using a dynamic model. The prototype’s experimental results show that the 3DOF actuator can generate 3DOF vibration.

A multimodal cyclic-label dequantized Gaussian process latent variable model (mCDGP) for visual emotion recognition is presented in this paper. Although the emotion is followed by various emotion models that describe cyclic interactions between them, they should be represented as precise labels respecting the emotions’ continuity. Traditional feature integration approaches, however, are incapable of reflecting circular structures to the common latent space. To address this issue, mCDGP uses the common latent space and the cyclic-label dequantization by maximizing the probability function utilizing the cyclic-label feature as one of the observed features. The likelihood maximization problem provides limits to preserve the emotions’ circular structures. Then mCDGP increases the number of dimensions of the common latent space by translating the rough label to the detailed one by label dequantization, with a focus on emotion continuity. Furthermore, label dequantization improves the ability to express label features by retaining circular structures, making accurate visual emotion recognition possible. The main contribution of this paper is the implementation of feature integration through the use of cyclic-label dequantization.

Smooth interactions between talkers can be realized by transmitting and receiving mutual video images and voices in remote communication. However, in such remote communication, it is difficult to generate a sense of unity and an interactive atmosphere because humans recognize screens as a boundary of the physical space. Therefore, it is essential to develop a communication system that can generate and share an interactive atmosphere and interaction-activated communication even if talkers are in remote places. In this study, we developed a speech-driven avatar robot system incorporating an estimation model that simulates the degree of activated communication based on the talker’s speech. The developed avatar robot system can visualize an interactive atmosphere while changing the complexion based on an estimated value. The effectiveness of the developed system was demonstrated by means of sensory evaluations.

This study aims to realize a precision grasp of unknown-shaped objects. Precision grasping requires a detailed understanding of the surface shapes such as concavity and convexity. If an accurate shape model is not given in advance, it must be addressed by sensing. We have proposed a method for recognizing detailed object shapes using proximity sensors equipped on each fingertip of a multi-fingered robot hand. Direct sensing of the object’s surface from the fingertips enables both avoidance of unintended collision during the approach process and recognition of surface profiles for use in planning and executing stable grasping. This paper introduces local surface curvature estimation to improve the accuracy of local surface recognition. We propose practical and accurate models to estimate local curvature based on various characteristic tests on the proximity sensor and to estimate the distance to the nearest point. In actual experiments, it was shown that it was possible to estimate the position of the nearest point with a mean error of less than 2 mm and to predict grasping stability in reasonable real-time for the object shape.

In this paper, we propose a novel algorithm for estimating road surface shapes and object heights using a fisheye stereo camera. Environmental recognition is an important task for advanced driver-assistance systems. However, previous studies have only achieved narrow measurement ranges owing to sensor restrictions. Moreover, the previous approaches cannot be used in environments where the slope changes because they assume inflexible constraints on the road surfaces. We use a fisheye stereo camera capable of measuring wide and dense 3D information and design a novel algorithm by focusing on the degree of division in a disparity image to overcome these defects. Experiments show that our method can detect an object in various environments, including those with inclined road surfaces.

Musculoskeletal systems are characterized by their structural softness and drive redundancy. The objective of this study was to reproduce these features using a tensegrity manipulator. The developed tensegrity manipulator was formed by replacing 40 of the 80 cables of class-1 tensegrity consisting of 20 struts with pneumatic cylinders to allow it to bend actively. This paper presents the design details of the manipulator and an analysis of its characteristics during various motions. We confirmed that this robotic platform could reproduce abstract features of the musculoskeletal system. In addition, we discuss the issues that must be addressed in the control of this robot according to the experimental results.

This paper proposes a method to improve the accuracy of 3D measurement of a stereo camera by marking a measured object using a line laser. Stereo cameras are commonly used for 3D measurement, but the accuracy of 3D measurement is affected by the amount of texture. Therefore, a new measurement system combining a stereo camera and a line laser is developed. The accuracy of 3D measurement with a stereo camera is improved by using a line laser to mark arbitrary points on the measured object and measuring the marked points, regardless of the amount of texture on the measured object. Because the laser is only used to mark points on the measurement target, calibration is not required with the stereo camera. Experimental evaluation showed that our proposed method can obtain millimeters.

With technological developments, the prospect of a human-robot symbiotic society has emerged. A soccer game has characteristics similar to those expected in such a society. Soccer is a multiagent game in which the strategy employed depends on each agent’s position and actions. This paper discusses the results of the development of a learning system that uses a self-organizing map to select behaviors depending on the scenario (two-dimensional absolute coordinates of the agent, other agents, and the ball). The system can reproduce the action-selection algorithms of all the players on a certain team, and the robot can instantly select the next cooperative action from information obtained during the game. Thus, common-sense rules can be shared to learn an action-selection algorithm for a set of both human and robot agents.