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This work reports on an innovative dewetting process of silver thin films to realize percolative nanoparticle arrays (NPAs) and demonstrates its application on highly sensitive pressure sensors. The dewetting process, which is a simple and promising technique, synthesizes NPAs by breaking the as-deposited metal film into randomly distributed islands. The NPA properties, such as the mean particle size and the spacing between adjacent particles, can be easily tailored by controlling the dewetting temperature, as well as the as-deposited metal-film thickness. The fabricated NPAs were employed to develop gauge pressure sensors with high sensitivity. The proposed sensor consists of a sealed reference-pressure cavity, a polyimide (PI) membrane patterned with an interdigital electrode pair (IEP), and a silver NPA deposited on the IEP and the PI membrane. The operational principle of the device is based on the NPA percolation effect with deformation-dependence. The fabricated sensors exhibit rapid responses and excellent linearity at around 1 atm. The maximum sensitivity is about 0.1 kPa−1. The advantages of the proposed devices include ultrahigh sensitivity, a reduced thermal disturbance, and a decreased power consumption. A practical application of this pressure sensor with high resolution was demonstrated by using it to measure the relative floor height of a building.

This work presents the development of highly efficient photothermal thin films (PTFs) and the demonstration of their application on miniaturized polymer-based soft actuators. The proposed PTF, which comprises acrylic-based black paint and EGaIn liquid metal (LM) microdroplets, serves as an excellent absorber for efficiently converting near-infrared (NIR) irradiation into heat for actuating liquid-crystal elastomer (LCE) actuators. The introduction of LM microdroplets into the PTFs effectively increases the overall thermal efficiency of PTFs. Miniaturized soft crawlers monolithically integrated with the NIR-driven LCE actuators are also implemented for demonstrating the application of the proposed PTF. The crawler’s locomotion, which is inspired by the rectilinear movement of snakes, is generated with the proposed PTF for inducing the LC-to-isotropic phase transition of the LCEs. The experimental results show that introducing LM microdroplets into the PTF can effectively reduce the thermal time constants of LCE actuators by 70%. Under periodic on/off NIR illumination cycles, the locomotion of crawlers with different dimensions is also demonstrated. The measurement results indicate that the proposed PTF is not only essential for enabling photothermal LCE actuation but also quite efficient and durable for repeated operation.

Atomic layer deposition (ALD)-based TiN electrode on ferroelectric HfZrO2 metal/ferroelectric/metal (MFM) capacitor and ferroelectric field-effect transistor (FeFET) is demonstrated experimentally with weight transfer, that is, $\Delta {P}$ , per pulse analysis through consecutive alternating potentiation/depression (Pot./Dep.) training pulses. The weight training pulse schemes are studied to have symmetric and linear synapse weight transfer to increase the accuracy and accelerate the deep neural network (DNN) training. With ALD TiN inserted, $\alpha _{p} / \alpha _{d} = -0.63$ / −0.84, asymmetry $\vert \alpha _{p} - \alpha _{d}\vert =0.21$ , and polarization modulation ratio (Pot./Dep.) = 97%/98% are achieved for MFM capacitor, and $\alpha _{p} / \alpha _{d} = -1.32$ / −1.88, asymmetry $\vert \alpha _{p} - \alpha _{d}\vert =0.56$ , and $G_{\text {max}} / G_{\text {min}} > 10\times $ are delivered for FeFET.

This work presents an ultra-sensitive iontronic wireless pressure sensor. The device consists of an inductor coil and a parallel-plate capacitor for pressure sensing. A microstructured iontronic film, which was embedded on the capacitor as dielectric layer, was the key element for enhancing the device performance. Assisted by the ultrahigh capacitance of electron double layers forming at the iontronic film/electrode interface, the sensitivity of the proposed device can be remarkably increased. Externally applied pressure on the device changes the capacitance, and then induces a shift in resonant frequency, which can be wirelessly retrieved by using the phase-dip technique. The measured pressure sensitivity of the proposed device was 0.014 mmHg-1, which is about 50 times larger than that of the device without iontronic film.

This paper presents the design, fabrication, and characterization of a thermal oscillator driven by fixed DC voltages. The proposed device consists of a miniaturized ultra-sensitive temperature sensor and a microheater. The temperature sensor was fabricated by depositing acrylate-based temperature sensing material with a positive temperature coefficient (PTC) effect on an interdigital electrode pair, and this was the key component that enabled oscillations by periodically switching the microheater on and off. The acrylate-based material, which was prepared by dispersing an acrylate copolymer with graphite particles, exhibits an order-of-magnitude variation in resistivity over a temperature change of a few degrees. The transient behavior of the fabricated device was measured, and the effects on different driving conditions with active cooling were measured and discussed. In addition, the measurement results also show that the temperature drift is not obvious in long-term testing, which indicates that the acrylate composite is quite reliable during repeated phase transition.

The 3D double layer Ω-type FETs with ferroelectric HfZrO 2 gate served for one-transistor (1T) architecture is demonstrated and studied for memory reliability. The high endurance is presented more than 106 cycles P/E with 4V. Multi-domain model integrated with TCAD is proposed by adding a coupling coefficient for the polarization gradient term of the free energy, and calculating for nanosheet GAA-FETs. The polarization orientation is assigned randomly by Gaussian distribution into individual domain for multi-dimensional 3D device simulation. The data retention is degraded due to depolarization field occurrence at the corner by modeling results. The feasible structure paves the candidate for emerging memory applications.

This work presents a wireless micro-heater with an integrated temperature regulator for the application of endohyperthermia treatment of restenosis. The proposed device uses a micromachined $L-C$ tank circuit for achieving a wireless resonant RF heating capability. An acrylate-composite-based circuit breaker integrated with a polymer film with sharp resistivity-temperature dependence characteristic was proposed for providing the temperature regulation feature. Wireless heating tests demonstrate the functionality of the breaker, which regulates the heater temperature rise below 8 °C with an RF excitation power of 100 mW. The preliminary measured results also showed that the proposed device potentially enables a reliable and safeguarded hyperthermia treatment through wireless microheaters.

In this work, we propose a wireless passive pressure sensor, which is designed for monitoring cardiovascular pressure. The device consists of an LC tank and a magnetic polymer film with tapered microstructures. The LC tank includes a micromachined parallel-plate capacitor and an inductor coil connected in series. External pressure applied on the magnetic polymer film changes the LC tank's resonant frequency, which can be wirelessly retrieved using the phase-dip technique. The corresponding relationship between the resonant frequency and the applied pressure is presented. The pressure sensitivity of the proposed device is about 0.113 MHz/mmHg in the pressure range of 0-300 mmHg. The measured results also showed that the proposed sensing mechanism has a wide range of linearity of pressure sensing.

This work presents a novel fully-compliant bistable device that only requires one actuator for switching between its two stable states. The proposed one-actuator bistable device consists of a curved-beam structure and a V-beam actuator. The proposed device, which is driven by a thermal actuator via moment input, is a significantly improved version of our previous work, consumes less die area, is of much less complexity, and does not require latching mechanisms. Characterization of the proposed device of different dimensions was performed and discussed. Preliminary measurement results show that a 50 pulse frequency of 7.5 V with 50% duty cycle applied to the V-beam actuator can continuously switch the device between the two stable states. The maximum switching rate is about 25 Hz.

This work presents the development of a tactile sensing array for continuous blood pulse wave monitoring. The polymer-based sensing device consists of two polydimethylsiloxane layers, which were patterned with microdomes transferred from nylon membrane filters. The microdomes form interlocked structures, which enable the tunneling piezoresistive effect and provide ultra-high sensitivity. The sensing array was designed in an 8 × 1 linear configuration, and the length-width ratio of each sensing element is about 8. This design facilitates the acquisition of blood pulse wave signals on the skin above a radial artery. The measured relationship between resistance and pressure force indicates that the sensor exhibits very high sensitivity (−6.08 kPa−1). The array sensing results revealed that crosstalk between the sensing elements was nominal. In addition, the repeatability testing also showed that the performance of the sensor was quite stable after 10,000 loading-unloading cycles.

A system integrating temperature, pressure and voice sensors is proposed for a smart oral appliance for use in diagnosing and alleviating obstructive sleep apnea (OSA). Using sealed bio-compatible packaging for intraoral use, this system is also capable of wireless charging and data transmission. This proposed design aims to enhance the effectiveness and convenience of OSA treatment.

Being the first demonstration of quasi-antiferroelertic Hf 1-x Zr x O 2 (QAFE-HZO, Zr=75%) negative-capacitance (NC) FET with non-hysteretic bi-directional sub-60mV/dec (SS for =51mV/dec, SS rev =53mV/dec, ΔV T FE overlap of negative dQ/dV FE for forward and reverse, indicating non-hysteretic QAFE-HZO.

In this work, we present an MXene-based flexible tactile and shear force sensing array using conductive multilayered MXene/carbon nanotube (CNT) composites as the sensing material. The multilayer sensing elements patterned on the nylon membrane substrate have excellent mechanical flexibility and elasticity. The fabricated multilayered MXene/CNT composites have advantages such as high piezoresistive sensitivity, anisotropic sensing capability, flexibility, and simplicity of fabrication. Furthermore, due to the relatively high aspect ratio of the patterned multilayer structure, the proposed sensing element has anisotropic characteristics, which can be employed for better shear sensing. The normal and shear force measurement results using the proposed device are also presented.

This work outlines the development of a wireless, flexible passive pressure sensor for monitoring cardiovascular pressure. The device employs Parylene C as a flexible substrate and is capable of being folded into a stent that is suitable for a catheter-based delivery system. An inductor–capacitor (LC) resonant tank, which consists of an inductor coil and a parallel-plate capacitor, was implemented for pressure sensing and wireless signal transmission. A multilayer MXene film embedded on the capacitor was used to enhance the pressure-sensing performance. External pressure on the device changes its capacitance, inducing a shift in the resonant frequency, which can be wirelessly retrieved using the phase-dip technique. The pressure responsivity of the proposed device is 0.093 MHz/mmHg, and the corresponding pressure sensitivity is 355 ppm/mmHg in the 0–250 mmHg pressure range.

This work presents a polymer-based capacitive sensor array capable of measuring both normal and shear forces. The capacitive sensing element consists of polydimethylsiloxane (PDMS) dielectric layers and gold electrode arrays. The PDMS dielectric layers were patterned with microdome structures using a simple micromachining technique with nylon membrane filters. Further, by using membranes with different pore sizes, the pressure sensitivity of the capacitive tactile sensor can be adjusted with ease. The measured relationship of capacitance versus pressure indicates that the sensitivity of sensors with interlocked interfaces is much higher than that of the sensor with planar films.

In this work, we present an ultra-sensitive temperature sensor for non-contact real-time respiratory monitoring. The sensing element of the proposed device is an acrylate-based temperature sensing material with positive temperature coefficient (PTC) deposited on an interdigital electrode pair. The acrylate-based material exhibits an order-of-magnitude variation in resistivity over a temperature change of a few degrees, and was capable of detecting tiny temperature changes induced by exhalation air flow. The transient behaviors of the fabricated device were measured. Also, the effects on different room temperatures and positions of the sensor were measured and discussed. The fabricated device possesses the advantages such as low cost, energy efficient, and simple operation compared to common existing methods.

This paper presents a novel LC-based passive wireless flexible pressure sensor that employs microstructured ferromagnetic films with tunable effective permeability. The proposed device consists of a micromachined planar spiral coil and a polymer film with cilia arrays (CAs) realized by the ferrofluidic instability principle. The effective permeability of the polymer film can be tuned by deforming the CAs with externally applied pressure, which can be estimated in turn by detecting the resonant frequency of the device using the phase-dip technique. The fabrication parameters for synthesizing different dimensions and densities of CAs were investigated as well. Devices of different CA densities were measured and discussed. The measured results showed that the device quality factor and phase change both increased with applied pressure. Due to this characteristic, the proposed device is advantageous over typical capacitive LC-based devices and performs better in wireless interrogation while maintaining the sensitivity of pressure sensing.

This work proposes a miniaturized wireless heating strip designed for safe wireless hyperthermia treatment against restenosis. The proposed heating strip was designed to be inserted into a stent that can be deployed in a blood vessel using a typical catheter-based delivery system. The device consists of a micromachined LC-based resonator and a microheater with a temperature regulator (MHTR). The LC-based resonator was employed to achieve wireless resonant RF heating, with the embedded MHTR serving as an electric current breaker in the resonator circuit to maintain the strip’s temperature within a desired range. An acrylate-based composite was used as the key material of the MHTR for temperature sensing and electric-current breaking. The MHTR allows smooth heating regulation in a passive manner, reducing the complexity of the device, and thus further facilitates the miniaturization of the device. The frequency responses to temperature of devices with and without an MHTR were studied. The performance of devices immersed in physiological saline solution was also examined in detail. Wireless heating tests demonstrated that the proposed MHTR effectively maintained the device temperature at around 45 °C with an output RF power of 500 mW. The results indicate that the proposed device potentially offers safe and reliable hyperthermia treatment.

This work presents a moment-driven bistable microdevice that requires only one actuator to switch between the device’s two stable states. The proposed device, which is a significantly improved version of our previous work, consists of two simple MEMS structures: a curved-beam structure and a V-beam actuator. Because the device is actuated by external moments, it consumes a smaller device area, and is less complex. In addition, the proposed device does not require latching mechanisms to lock the states. The closed-form design criteria for the proposed device were derived and validated with experimental measurement results. Transient bistable switching behaviors of the device were measured by using a vibrometer. Preliminary measurement results showed that the device can reliably switch between two stable states at 40 Hz with an actuation voltage of 10 V.

The spectrometer was used to measure the wavelength of illumination, but the intensity of the spectrometer was large because of its complex optical path and component. In contrast, the photo diode (PD) was applied to detect the light intensity, but the total intensity volume was detected instead of each wavelength. Therefore, the novelty sensor was developed to measure the lighting dose that irradiated by the light at specific wavelengths. The light emitted diode (LED) at different wavelengths were fabricated by different semiconductor processes and doping different materials, and it will emit the light when the current pass through the component. Moreover, the reverse effect would be induced and the electron of materials would move run and the current would be activated when the LED was irradiated by the illumination source. Therein, the LED as a dose sensor has a characteristic that was only being activated by the light source at the same wavelength. In the experiment, three different colors of LED (red-670nm, green-528nm, blue-485nm) were employed to be the dosage sensor, which called as light-receiving diode (LRD), and the same LED were also the light source to irradiate the dosage sensor. From the results, the relationship between the intensity and the irradiance distance and angle was established, and the minimum variation between the measured and evaluated intensity of 3 % was obtained. In the future, the actual lighting dose could be evaluated from the presented information about the manuscript and without wearing the detection module in the lighting therapy process. Moreover, the evaluated could be recorded to investigate the effect between the lighting dose and physiological mechanisms or diseases.

The pulse pressure variation associated with arterial blood flow is a valuable indicator for early diagnosis of cardiovascular diseases, which could lead to lots of health problems if left untreated. To detect the subtle wrist artery pressure, a cuffless wearable integrated system using a tunneling piezoresistive sensor, which achieves ultrahigh sensitivity, is presented in this paper. After the readout circuit amplifies and converts the pulse pressure-induced signal, a wireless communication module transmits the data to intellectual devices and eventually to the cloud storage. Real-time and sustainable pulse pressure monitoring is demonstrated from sensor detection to cloud computing. Through the digital signal processing, long-term pulse pressure monitoring improves the accuracy of cuffless applications, and measured data can accomplish cardiovascular event fast screening after being processed by Hilbert Huang transform (HHT), pulse rate variability (PRV), and multi-scale entropy (MSE) analysis.

In this work, a mandibular advancement device integrated with a highly-sensitive pressure sensing array and a system-on-a-chip (SoC) is presented. The device is designed for monitoring the tongue pressure distributions of patients for treating orofacial disorders such as obstructive sleep apnea syndrome and snoring. The pressure sensing array consists of a conductive polymer assembled with interdigital electrodes, and the SoC chip possesses the capabilities of array scanning and RF transmission. Microdome structures were patterned on the conductive polymer for enhancing the sensitivity of pressure sensing. The proposed device exhibit excellent sensitivity and rapid response. The pressure patterns induced by the tongue positions before and after the tongue drop during sleep were also presented.