Hiroyuki Ito

• Professor (Associate) at Tokyo Institute of Technology

This paper presents a dual-detection range single-axis MEMS accelerometer and an octagonal gold proof-mass structure, which suppresses the proof-mass warpage caused during MEMS process. It comprises two devices; One device offers a detection range of 0.1g–10g (1g = 9.8m/s ² ), while the other, a large, hollow structure surrounding the central devic...

As global attention on sustainable and ethical food systems grows, animal welfare-friendly products (AWFP) are increasingly recognized as essential to addressing consumer and producer concerns. However, traditional research often neglects the interdependencies between production, retail, and consumption stages within the supply chain. This study ex...

Necking and barreling deformation behaviors occurred simultaneously during the bending test of a single-crystal gold micro-cantilever (sample A) with the loading direction parallel to the [1-10] orientation and the neutral plane parallel to the [110] orientation. In contrast, for another single-crystal gold micro-cantilever, sample B, with the load...

Long-term monitoring of biomedical signals is crucial for modern clinical treatment of neurological disorders such as epilepsy. Encoding epileptic seizures with partial synchronization using a spiking neural network (SNN) offers a promising avenue as such networks can be implemented on ultra-low-power neuromorphic processors. Indeed, such bio-inspi...

This work presents a neural network DPD for mmWave RF-PAs. Differently from existing neural network-based DPDs, the neural network in the proposed DPD does not reside in the forward data path. Instead, it estimates the polynomial coefficients from the complex Fourier amplitudes of harmonics during a calibration sweep. It can compensate for PA nonli...

Electrodeposited Au-based micro-electromechanical system (MEMS) capacitive accelerometers with Ti/Au multi-layered structures are promising devices for detecting very low accelerations due to the high mass density of Au. On the other hand, the large difference in the coefficients of thermal expansion (CTE) between Ti and Au causes warpage in the el...

This paper describes a design technique for serpentine spring with the edge span beam L/2. In order to improve design accuracy, we investigate the key structure parameters influenced by the fabrication process for MEMS device, comparing FEA (finite element analysis) and analytical models. It is found that the Fedder model as the analytical model is...

The development of ultralow-power analog front ends for edge artificial intelligence (AI) is actively pursued; however, these front ends suffer from low-frequency selection accuracy, leading to increased training loads for the AI components and higher testing costs. In this article, we propose a novel circuit that fundamentally addresses these issu...

Recently, MEMS accelerometers employing Au components prepared by electrodeposition are reported to have a small size whiling retaining a high sensitivity [1], which is mainly contribute by Au’s high mass density, as shown in Fig. 1. Detections of body tremors and muscular sounds are realized using this highly sensitive MEMS accelerometer [2]. Howe...

A wireless sensor terminal module of 5cc size (2.5cm × 2.5cm × 0.8cm) that does not require a battery is proposed by integrating three kinds of circuit technologies. (i) a low-power sensor interface: an FM modulation type CMOS sensor interface circuit that can operate with a typical power consumption of 24.5μW was fabricated by the 0.7-μm CMOS proc...

A signal flow graph (SFG) representation of small-signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of th...

The growth of Artificial Intelligence (AI) and Internet of Things (IoT) sensors has given rise to a synergistic paradigm known as AIoT, wherein AI functions as the decision-maker and sensors collect information. However, a substantial proportion of AIoT rely on cloud-based AI, which process wirelessly transmitted raw data, increasing power consumpt...

In this paper, new circuit techniques are proposed and applied for low-power, high-resolution capacitance sensing. The first is a CMOS-inverter-based RC oscillator that consists of a resistor, a capacitor, and three inverters, allowing it to operate at low supply voltage and low power with a wide sensing range. The second is a voltage-integration f...

p>Signal flow graph (SFG) representation of small-signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of th...

The behavioral monitoring of farmed animals such as cattle is a fundamental element of precision farming in that it enables unobtrusive ongoing health monitoring. This application presents two ubiquitous challenges typical of sensing applications of internet-of-things: limited dataset size and dataset imbalance. Recently, data augmentation has emer...

The synchronization of chaotic systems has been extensively studied based on diverse coupling schemes and media which allow almost unaltered energy exchange over the entire spectral range of oscillation. Less is known about the dynamics of systems encompassing couplings that restrict interaction to a narrower frequency interval, such as through ban...

Shifts in protein production methods are an emerging challenge toward realizing a sustainable society. This paper aims to examine preferences among Japanese consumers regarding attributes of beef mince and its substitutes, to develop consumer segments based on these preferences, and to explore the segment with higher acceptance of replacement from...

Transistor-based chaotic oscillators are known to realize highly diverse dynamics despite having elementary circuit topologies. This work investigates, numerically and experimentally using a ring network, a recently-introduced dual-transistor circuit that generates neural-like spike trains. A multitude of non-trivial effects are observed as a funct...

A method to predict lightning by machine learning analysis of atmospheric electric fields is proposed for the first time. In this study, we calculated an anomaly score with long short-term memory (LSTM), a recurrent neural network analysis method, using electric field data recorded every second on the ground. The threshold value of the anomaly scor...

This paper describes a simplified analytical model of a damping constant ${b}$ to design a MEMS capacitive accelerometer using the multi-layer metal technology. The proposed model is introduced by combining the theoretical equation with the approximate form factor obtained by the measured data. In order to create the model, we fabricated several...

This paper describes a highly sensitive microelectromechanical systems (MEMS) accelerometer sensor module to measure micro muscle sounds. Regarding the drift mechanism, we focus on charged particles based on residual water related to MEMS fabrication. Based on temperature programmed desorption analysis and electrical experiments, it is clarified th...

Signal flow graph (SFG) representation of small- signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of the...

Signal flow graph (SFG) representation of small- signal responses of nonlinear microwave circuits around a large-signal operating point is developed using the X-parameters. It is shown that, unlike the SFGs for linear circuits, negative-frequency nodes need to be included explicitly. The development elucidates the circuit-operational meaning of the...

A recently-introduced autonomous electronic chaos generator which has an elementary circuit topology not intentionally derived from canonical oscillators is considered. It comprises a bipolar junction transistor, a resistor, two inductors and one capacitor. Though its notable generative potential has been remarked, its functioning principles have t...

An electronic chaos generator involving cross-coupled inverter rings with lengths equal to the smallest odd prime numbers is considered, and a spatiotemporally-varying control parameter, hypothetically corresponding to a physical variable to be sensed, is introduced akin to a baseband signal. It is shown that, owing to the fine-grained structure of...

Precision livestock farming promises substantial advantages in terms of animal welfare, product quality and reducing methane emissions, but requires continuous and reliable data on the animal's behavior. While systems suitable for use within the barn exist, grazing over long distances poses challenges. Here, we address this issue by proposing an ul...

Cow behavior monitoring is critical for understanding the current state of cow welfare and developing an effective planning strategy for pasture management, such as early detection of disease and estrus. One of the most powerful and cost-effective methods is a neural-network-based monitoring system that analyzes time series data from inertial senso...

We have developed a broadband and high-precision terahertz (THz) frequency counter based on a semiconductor-superlattice harmonic mixer (SLHM). Comparison of two THz frequencies determined using two independent counters and direct measurement of frequency-stabilized THz-quantum cascade lasers by a single counter showed a measurement uncertainty of...

Ti/Au multi-layered micro-cantilevers with complex three-dimensional structures used as micro-components in micro-electromechanical systems (MEMS) sensors were prepared by lithography and electrodeposition, and the effective Young’s modulus was evaluated by the resonance frequency method and finite element method simulation. Effects of the constrai...

Abstract An injection‐locked divider oscillator that converts a 6‐GHz‐band signal into a 3‐GHz‐band signal was developed. The injection‐locked divider oscillator was specifically designed to lock on the clock transition frequency of 87Rb of 6.824 GHz to provide a laser modulation signal at 3.417 GHz for an on‐chip coherent population trapping atomi...

This study reports mechanical properties of single-crystal pure gold toward for applications as movable components in micro-electrical-mechanical system (MEMS) inertial sensors requiring high sensitivity. Gold is commonly applied in electronic devices because of the excellent corrosion resistance, chemical stability, and conductivity. Recently, MEM...

In recent years, MEMS (microelectromechanical systems) devices are required to have high functionality and small size, especially for MEMS acceleration sensors, and sensitivity of a MEMS acceleration sensor is highly dependent on the Brownian noise [1,2]. The Brown noise is known to be inversely proportional to mass of movable parts in the sensor,...

Strengthening of electrodeposited Au-based materials is achieved by co-electrodeposition with TiO2 nanoparticles dispersed in a sulfide-based gold electrolyte. TiO2 content in the composite film is adjusted by concentration of the TiO2 in the gold electrolyte. Effects of the TiO2 content on surface morphology, crystalline structure and microstructu...

Sample geometry effects on mechanical strengths of gold micro-cantilevers are evaluated by a micro-bending test. Six micro-cantilevers with the same length of 50 μm are prepared, and the width and the thickness are varied to examine individual effects on the yield stress. The yield stress increases from 428 to 519 MPa when the thickness decreases f...

This paper reviews the feature of newly developed CMOS-MEMS (microelectromechanical systems) and MEMS accelerometers and its application for a diagnosis of Parkinson’s disease. In order to realize micro-G (1G=9.8m/s ² ) level sensing, we propose and develop capacitive MEMS accelerometers with Au proof mass using the multi-layer metal technology. In...

Electrodeposited gold is used in movable micro-components of micro-electro-mechanical systems (MEMS) devices to allow further enhancement in the sensitivity and miniaturization of the device [1]. Mechanical strengths of gold are low among materials commonly used as structure materials in electronic devices. Electrodeposition method is advantageous...

Microelectromechanical systems (MEMS) inertia sensors, such as MEMS accelerometers, are now widely used for a variety of applications in automotive, industrial, healthcare, entertainment, consumer handheld electronics, etc. In this paper, we present our recent progress of a highly sensitive CMOS-MEMS inertia sensor and its application to early-stag...

This paper reports fabrication of AuCu alloy microcantilevers by alloy electroplating with a non-cyanide electrolyte and evaluation of the Young’s modulus by a resonance frequency method. Length of the microcantilever is ranged from 50 ∼ 1000 μm, and the width is from 10 ∼ 20 μm. Effects of the applied current density (CD) on the composition, morph...

Emerging applications across environmental, biomedical, and structural monitoring require the measurement of physical variables over extended regions. Because addressing many sensors individually can result in impractical bandwidth and power requirements, there is a need for distributed sensing approaches wherein readouts are obtained directly at t...

Natural and engineered networks, such as interconnected neurons, ecological and social networks, coupled oscillators, wireless terminals and power loads, are characterized by an appreciable heterogeneity in the local connectivity around each node. For instance, in both elementary structures such as stars and complex graphs having scale-free topolog...

Hierarchical structures of 20 nm grains embedded with twins are realized in electrodeposited Au–Cu alloys. The electrodeposition method allows refinement of the average grain size to 20 nm order, and the alloying stabilizes the nanoscale grain structure. Au–Cu alloys are face-centered cubic (FCC) metals with low stacking fault energy that favors fo...

MEMS(microelectromechanical systems) accelerometers are key devices for IoT (Internet of Things) technology. Throughout the technical progress, the resolution of detecting acceleration has been required to be the level of micro-G (1 G = 9.8 m/s ² ) in spite of small sensor size. In order to solve the problem, we proposed capacitive MEMS acceleromet...

Au-Cu alloy micro-cantilevers are fabricated from Au-Cu alloy films electrodeposited at different current density. Bending deformation behaviors of the Au-Cu alloy micro-cantilevers are evaluated for applications as components in MEMS devices. Au-Cu alloy films with smaller grain size and higher copper content are obtained when a higher current den...

This paper reports Cu-alloying effects on the structure stability of gold-based micro-cantilevers evaluated by long-term vibration test for applications as movable micro-components in MEMS devices. Au–Cu alloy micro-cantilevers are fabricated by lithography and Au–Cu alloy electrodeposition. The composition is affected by the applied current densit...

The generation of chaotic signals is relevant to a multitude of applications across telecommunications, random number generation, control and the realization of distributed sensing systems; in addition, networks of coupled chaotic oscillators replicate diverse emergent phenomena occurring in considerably larger biological neural systems. However, t...

This study reports mechanical property enhancement observed in micro-cantilevers composed of Au/Ti bi-layered structure evaluated by micro-bending test. A layer of gold film is electrodeposited on a cold-rolled titanium plate using a sulfite-based gold electrolyte. Specimens used in the micro-bending test are micro-cantilevers fabricated by focus i...

Long-term structure stability of micro-cantilevers employing the Ti/Au layered design is evaluated by vibration test to demonstrate the advantage toward design of MEMS micro-components. Length of the micro-cantilevers is ranged from 200 to 1000 μm, and the width is at 20 μm. Two types of the Ti/Au layered design are evaluated in this study. One is...

We describe microgravity generation and the resolution evaluation results of a sub-1-mG microelectromechanical system (MEMS) accelerometer (1 G = 9.8 m/s²). To realize input acceleration below 1 mG, we show the principle of generating microgravity acceleration by adjusting the tilt angle. The change in acceleration induced by a tilting board is qua...

We developed a microwave oscillator and a micro electromechanical systems-based rubidium cell for the miniaturization of atomic clocks. A thin-film bulk acoustic resonator (FBAR) having a resonant frequency of the fundamental mode in the 3.5 GHz band was employed instead of a crystal resonator. It delivers a clock transition frequency of Rb atoms o...

DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a future Japanese space gravitational-wave antenna. The most important objective of DECIGO, among various sciences to be aimed at, is to detect gravitational waves coming from the inflation of the universe. DECIGO consists of four clusters of spacecraft, and each cluster consists...