MEMS (Micro Electro Mechanical Systems) is a technology that is used to incorporate sensors, actuators, microstructures, and circuits on chips by using a combination of various technologies with semiconductor process. MEMS are also used in robotics and mechatronics since they can provide compact, low-cost functional components that play crucial roles in their respective systems. We would like to elaborate on the history of MEMS technology, whose initial development started around 1970.

In 1960s, Dr. Isemi Igarashi of Toyota Central R&D Labs., Inc. in Japan developed a semiconductor pressure sensor of piezo-resistance type. In 1980s, the pressure sensors were used to control automobile engines to clear exhaust gas regulations and thus contributed to solving environmental issues. In 1990s, semiconductor acceleration sensors were used for passive safety technologies to detect collision of automobiles and activate air bags, which resulted in decrease in traffic fatalities. In 2000s, an active safety system with gyro sensors was developed to detect and control spinning of a vehicle. In future, space recognition sensors with optical scanners to measure light propagation time and detect distance to an object will be used for autonomous driving.

For smartphones, a microphone, an acceleration sensor, and a gyro sensor are used in user interface, and a film bulk acoustic wave resonator (FBAR) is used in a wireless communication filter. For projectors, the built-in circuit of a mirror array system is used to move mirrors placed in an array. After the development of projectors, films have not been used in movie theaters.

MEMS are also widely used in medical and biological fields, such as blood pressure measurement. Esashi began research on a semiconductor ion sensor ISFET (ion sensitive field effect transistor) in 1971. ISFET detects ion concentration in electrolyte by exposing the insulating film of an insulated gate transistor to the liquid. He set up a prototyping facility when he was a graduate student and wrote only one paper on this research, although the prototyping facility was used afterwards. The ion sensor was certified under the Pharmaceutical Affairs Law after a 12-year application process and was used as catheter-type pH sensor to diagnose reflux esophagitis. MEMS are widely used for minimally invasive medical treatment, which causes minimum damage to human body. Moreover, MEMS are used as disposable sensors to prevent infection or as implanted devices.

In addition, MEMS are used for production inspection and scientific instrument, including scanning probe microscopes (SPMs), which observe atoms using extremely small nano-probes, and probe cards that simultaneously test several integrated circuits on a wafer using aligned probes.

When he was an associate professor, Esashi improved the prototyping facility that he made when he was a student and made a large scale integrated circuit (LSI). After he became a professor, he accepted researchers from more than 130 companies and developed MEMS using the prototyping facility to develop a product through the academia-industry collaboration. He realized integrated MEMS by combining LSI and MEMS. This includes a system of many tactile sensors attached on the body surface of a safe robot for real-time detection of contact through packet communication.

After he retired from the university, he developed a “prototype coin laundry,” which enables companies to do develop without having their own prototyping facility. The prototype coin laundry is a system where engineers can use the prototyping facility to develop devices, and the system has been managed by successors. Unlike integrated circuits for which standardization is easy, standardization of MEMS is challenging because of difficulty in development. It is necessary to access various knowledge for the development of MEMS, and ... [View PDF for the rest of the abstract]

This paper presents a review of the current applications of Micro-Electro-Mechanical Systems (MEMS) in the robotics and industrial applications. MEMS are widely used as actuators or sensors in numerous respects of our daily life as well as automation lines and industrial applications. Intersection of founding new polymers and composites such as silicon and micro manufacturing technologies performing micro-machining and micro-assembly brings about remarkable growth of application and efficacy of MEMS devices. MEMS indicated huge improvement in size reduction, higher reliability, multi-functionality, customized design, and power usage. Demonstration of various devices and technologies utilized in robotics and industrial applications are illustrated in this article along with the use and the role of silicon in the development of the sensors. Some future trends and its perspectives are also discussed.

This paper describes the fabrication and characterization of a prototype wettability switching soft skin device that dynamically switches its surface morphology between flat and rough states. The device, which consists of a 1-μm-thick polydimethylsiloxane (PDMS) deformable diaphragm on a PDMS substrate with a micro-bump arrays, was successfully formed with a high fabrication yield by a novel method of device releasing from a dummy substrate. In buffered hydrofluoric acid (BHF) solution, a sacrificial layer of a novolak-resin-based resist was able to be rapidly released from the OH-terminated SiO₂ surface of the dummy substrate, probably due to the breaking of hydrogen bonds at the interface. The wettability of the fabricated device was reversibly switched using micro-diaphragm deformation by varying the inner pressure. When a droplet was placed on the surface in the rough state, a large contact angle of approximately 140° was obtained, close to the Cassie mode with air in the concave-deformed PDMS micro-diaphragms, which indicated a high surface hydrophobicity. During cyclic switching between the rough and flat states after second switching, the contact angle reversibly changed between 106° and 120°, in good agreement with the Wenzel mode, where the micro-diaphragm surfaces were fully wet. Additionally, we observed that the droplet did not move even on the tilted device.

In the study, we investigated a detection method of partial contact of an object owing to curved or uneven surface of the contact object by a tactile sensor. The sensor is developed using three microcantilevers embedded in a polydimethylsiloxane (PDMS) bump. First, three bumps were employed to place a bump for each cantilever. It was possible to detect a contact position because the resistance change in the strain gauge on the cantilever under each bump significantly depended on the contact/non-contact state of each bump. Second, a tactile sensor with high-density arrangement of microcantilevers was used to detect partial or tilted contact situations. The results indicated that the output of a tactile sensor with high-density arrangement of microcantilevers reflected partial or tilted contact. It is suggested that a tactile sensor with multiple bumps and high-density microcantilevers allows for more dexterous gripping control based on the shape of the object and contact angle.

In the present report, we have developed a tactile sensor with fingerprint-like array of contactors for obtaining the surface distribution of tactile information in high spatial resolutions. Six high resolution sensing modules of contactors with biaxial detectors were integrated in line at a pitch of 500 μm, the typical pitch of fingerprint ridges. Each sensing module independently detected the micro surface shape and locally generated frictional force on the object surfaces. Mechanical analysis of the fabricated sensors showed good sensitivities and highly linear responses. Consequently, the measured detection resolutions of surface shape and frictional force were 0.17 μm and 9.9 μN, respectively. The experimental performance evaluation of fabricated sensor was measured in the distribution of tactile information by sweeping the sensor with a yaw angle. Additionally, the 3D surface shape of weave structure and surface distribution of frictional force in a woven fabric with 0.4 mm pitch of threads in high spatial resolution was clearly visualized/observed. Moreover, the directionality of tactile information of the fabric surface distribution was successfully realized using the tactile sensor with the array of contactors by sweeping in different directions.

A tactile sensation device using micro-electromechanical system (MEMS) has been developed. This device is integrated with a haptic sensation robot for use as fingers. The tactile device must be miniaturized to enable attachment of the actuator mechanism to the fingers. Therefore, we used MEMS technology for this device. The device is composed of an interface part fabricated by 3D printing, pins, and MEMS cantilever-type actuators. It has the ability to stimulate the mechanoreceptors of the fingertips. The device and robot can display not only high-resolution images of the fingertips but also the repulsion force during finger operations such as tool holding and rotation. We have not yet achieved the final device because of fabrication problems. In this paper, we explain the details, progress of development, and results of trials on the prototype device.

This study proposes a sensing system that can sense force and temperature at the same time. The system consists of MEMS-LSI integrated tactile sensor devices called sensor nodes, a field-programmable gate array (FPGA) based relay node, and a host PC. For real-time temperature and force data acquisition, a time-sharing force and temperature task processing mechanism was implemented with a dedicated computer architecture in the FPGA configuration and the host program. This study firstly reports the temperature dependency analysis of a capacitive sensor readout circuit in the sensor node by circuit-level simulation. With a fabricated sensor node, sensor output data were measured and analyzed with varying temperatures and applied force. Based on the measured data, linear multiple regression equations for temperature compensation of sensed force data were developed. In the temperature range of 24.8°C–60°C, the average/maximum force errors when considering the temperature effect were −0.98%/65% without the compensation, and 0.072%/17% with the compensation, respectively. One cycle time of temperature and force sensing for one sensor node was 113 ms on average. The experimental results showed that real-time temperature and force sensing and temperature compensation for accurate force sensing could be achieved successfully. The study also demonstrated the system with hot-coffee cup and finger touch examples.

Because of the power density advantages of fluid power systems, many researchers have developed microactuators using homogeneous electrorheological (ER) fluids (ERFs) for applications to various micromachines. An ER valve, as a critical component of the ER actuator, can control ERF flow by the apparent viscosity increase resulting from the applied electric field without any mechanical moving parts. Hence, it is adequate for the miniaturization of a fluidic microactuator. However, it is not easy to integrate rigid ER valves into soft microrobots. To overcome these limitations, we developed a novel elastic ER microarm using flexible ER valves (FERVs) in this study. Each microarm consists of an FERV, a movable chamber, and a displacement constraint element, so that it bends with the inner pressure controlled by the FERV. We proposed and developed a micro-electromechanical system fabrication process for the FERV, movable chamber, and displacement constraint element. By utilizing the proposed method, we successfully fabricate a FERV-integrated microarm. The characteristics of the FERV were experimentally clarified. In addition, the bending motion of the FERV-integrated microarm was demonstrated by experiments and verified by finite-element method simulation. This ER microarm was shown to be feasible for an ER microgripper composed of multiple microarms.

We design, fabricate, and measure high-speed resonant varifocal mirrors for a reflective type focus scanning optical element. A circumference supported type mirror and a node supported type mirror with a 1 mm diameter driven by an electrostatic actuator are investigated. In the node supported type, a larger amplitude compared to that of the circumference supported type was obtained. The fabricated mirror could operate at approximately 450 kHz with axisymmetric deformation. The focal length was calculated to be ±28 mm at an applied total voltage amplitude of 150 V.

Humans do not feel pain when bitten by mosquitos; therefore, we have attempted to develop a microneedle that mimics the puncturing mechanism of mosquitos. We have quantitatively evaluated the puncturing performance of the developed microneedle by puncturing an artificial skin made from polydimethylsiloxane (PDMS), a kind of silicon rubber. Unlike the mono-layered PDMS, however, animal skin including human skin is structured to have a hard stratum corneum, epidermis and dermis over soft subcutaneous tissue. In this paper, we propose an artificial skin having a two-layered hard/soft structure, constructed from PDMS with a human-hair-derived keratin film adhered onto the top surface. We evaluated the hardness of the keratin film (Young’s modulus) and found that it could qualitatively simulate the hard layers of the skin including the stratum corneum. The artificial skin we developed reproduced the following phenomena: the decrease in resistance force of animal skin at the point when the needle penetrates the surface followed by variation in resistance due to the stick-slip phenomenon as the needle penetrates more deeply.

As a part of the development of a minimally invasive hollow microneedle designed to mimic a mosquito proboscis, we evaluated the relationship between the needle inner diameter (ID) and blood sucking performance. If the ID is thinned to reduce pain upon piercing skin, blood could clog the tube owing to coagulation, and a sufficient volume of blood might not be obtained. In this study, laser stereo-lithography is used to easily fabricate microtubes of several sizes, at 20–50 μm ID and a fixed length of 500 μm, through which human whole blood is sucked by a vacuum pump. The results indicate that the ID of the tube must be at least 20 μm to prevent hemolysis and at least 50 μm to enable extraction of 200 μL of blood, which is necessary for general blood tests. Moreover, anticoagulant coating applied on the inner wall prevents the clogging of blood and increases the volume of extracted blood.

The shape of the needle tip that is currently used in the medical field is a “lancet point,” which is a diagonally cut cylindrical pipe, further cut on both sides. The shape of the needle shank is typically cylindrical. In this paper, tip and shank shapes that differ from the standard shape are experimentally investigated for the purpose of reducing puncture resistance. Microneedles of various cross-sectional shapes, such as polygonal and star-like, were fabricated using stereo laser lithography. Before the needle penetrates the skin, sharp edges at the needle tip may be effective to generate a stress concentration on the skin, inducing a skin fracture. After the needle penetrates the skin, corners in the cross section of the needle shank may effectively reduce the frictional resistance because the contact area between the skin and needle is limited at the corners. A needle insertion experiment was conducted against an artificial skin made of polydimethylsiloxane. The puncture resistance decreased respectively for the circular needle, polygonal needle, and star-shaped needle. For the star-shaped needles, the maximum resistance decreased as the number of corners (N) decreased. For the polygonal needle, the maximum resistance increased as N increased from 3 to 5; however, there was no observable difference for N from 6 to 8. The experimental results show that a triangular star-shaped microneedle is the most effective in reducing the puncture resistance.

Herein, using the micromachining technology, we propose a microneedle delivery mechanism that is similar to the lead delivery mechanism for a mechanical pencil. This mechanism involves three parts: a needle grasping part, a needle advancing part, and a needle retainer. This mechanism advances the needle by repeating the following steps: 1) fix the needle in the grasping part; 2) simultaneously advance the grasping part and the needle using the advancing part; 3) release the needle from the grasping part; 4) retreat the grasping and the advancing parts to their initial positions. This operation advances the needle very slowly, thereby allowing the needle to puncture the skin without buckling, even if the needle has a narrow diameter. Each component of the puncture device was cut from a plastic plate using a femtosecond laser. We evaluated the performance of the device for a stainless steel needle of φ100 μm, and were successful in delivering the needle at approximately 100 μm/cycle under a no-load condition. We also succeeded in puncturing the same needle into a hydrogel (Young’s modulus of ∼0.08 MPa) using this device.

Polylactic acid (PLA) microneedles have been usually fabricated by injection molding. Herein, we consider microneedles that mimic the maxillae of mosquito proboscises, which have sharp tips with jagged harpoon-like protrusions. In case of such microneedles, filling the melting PLA resin up to the tip of the mold trough without burrs is challenging. To address this issue, we have proposed a new microneedle fabrication method in this paper. In this method, the needle with the desired shape was obtained from a PLA sheet by femtosecond laser machining. The needle was turned by 90°, and its tip further cut obliquely with the laser for three-dimensional (3D) sharpening. Tensile and buckling tests were conducted by using a test piece cut out from the PLA sheet. It was experimentally established that the strength and Young’s modulus along the sheet’s stretch direction are higher than those along its perpendicular direction. The 3D sharpened PLA microneedle successfully penetrated an artificial skin made of polydimethylsiloxane. A pair of microneedles were alternately vibrated against each other, mimicking the motion of mosquito two maxillae. With this alternate vibration, the resistance force during insertion was found to be lower compared to that without vibration.

A biodegradable chitosan-acetate microneedle is developed based on the proboscis of a mosquito, which consists of chitin and protein. The formability of chitosan, which is a deacetylated compound of chitin, is improved by dissolving it in dilute acetic acid. Thereafter, the dissolved chitosan is coated around an Al wire by a dip-coating method, followed by drying. Afterward, the Al wire is removed by etching using an alkaline solution to form the chitosan micropipe. Subsequently, the micropipe is baked at 200°C for 0.20 min. The optimum baking time was found to be 17 min. Finally, the micropipe is cut and its tip sharpened to transform it into a microneedle with a length, an outer diameter, and an inner diameter of 4 mm, 150 μm, and 100 μm, respectively. The Young’s modulus of the fabricated chitosan microneedle is approximately 10 GPa. This microneedle could be inserted into an artificial skin made of silicone rubber without buckling, and it could aspirate blood from a frog at a rate of 2.5 μL/s.

All terrain cranes often work in construction sites. Blind spots, limited information, and high mental workload are problems encountered by crane operators. A top-view camera mounted on the boom head offers a valuable perspective on the workspace that can help eliminate blind spots and provide the basis for assisting operation. In this study, a visual 2D map of a crane workspace is generated from images captured by a top-view camera. Various types of information can be overlaid on this visual 2D map to assist the operator, such as recording the operation and projecting the boom head’s expected path through the workspace. Herein, the process of generating a visual map by stitching and locating the boom head trajectory in that visual map is described. Preliminary proof-of-concept tests show that a precise map and projected trajectories can be generated via image-processing techniques that discriminate foreground objects from the scene below the crane. The location error is analyzed and verified to confirm its applicability. These results show a way to help the operator make more precise operation easily and reduce the operator’s mental workload.

Together with wireless distributed sensor technologies, the connectivity control of mobile robot networks has widely expanded in recent years. Network connectivity has been greatly improved by theoretical frameworks based on graph theory. Most network connectivity studies have focused on algebraic connectivity and the Fiedler vector, which constitutes a network structure matrix eigenpair. Theoretical graph frameworks have popularly been adopted in robot deployment studies; however, the eigenpairs’ computation requires quite a lot of iterative calculations and is extremely time-intensive. In the present study, we propose a robot deployment algorithm that only requires a finite iterative calculation. The proposed algorithm rapidly estimates the robot positions by solving reaction-diffusion equations on the graph, and gradient methods using a Laplacian kernel. The effectiveness of the algorithm is evaluated in computer simulations of mobile robot networks. Furthermore, we implement the algorithm in the actual hardware of a two-wheeled robot.

This paper proposes a method to detect cutting points on tomato peduncles using a harvesting robot. The main objective of this study was to develop automated harvesting robots. The harvesting robot was equipped with an RGB-D (Red, Blue, Green, and Depth) camera to detect peduncles and an end effector to harvest tomatoes. Robots must be able to detect where to cut crops during harvesting. The proposed method was used to detect the cutting points on peduncles using a point cloud captured by the RGB-D camera. Our robot was used to identify the cutting points on target tomato peduncles at an actual farm to demonstrate the effectiveness of our approach experimentally. Using the proposed method, the harvesting robot could detect the cutting points on tomatoes.

Humans have characteristic forearm and hand structures, and most of the previously developed humanoids are not equipped with them. The human forearm has a radioulnar structure composed of two long thin bones, and the human hand has flexibility to move to fit the object and strength to support the human body. Therefore, we develop a novel miniature bone-muscle module integrating bone and muscle structures, and realize the human radioulnar structure. In addition, we develop a novel finger, which is flexible and robust, by using machined springs. We integrate them and construct a forearm and hand system which imitates human joint structures, muscle arrangements, proportion, and weight. Using this forearm and hand system, we realize several human skillful motions.

This paper describes system developments for integrating control systems of Manzai robot duos that automatically generate Manzai scripts from Internet articles based on given keywords, as well as improvements in the scalability of the integrated control system. Component-based Manzai robots controlled by RT-Middleware have been developed. However, conventional Manzai robot systems, the control systems of which are individually developed, experience some difficulties in interface integration and system maintenance as well as in scalability. In this study, we built a Manzai robot system excellent in reusability, maintainability and scalability by separating the common part from the hardware-dependent part by using the RT components of RT-Middleware. We also verify the reusability and scalability of the hardware-constrained component groups by implementing the Manzai robot control system into ready-made robots with different types of mechanism. We proved the effectiveness of the developed Manzai robot control system on its implementation results.