A new touch mode capacitive pressure sensor with two deformable diaphragms

To achieve the characteristics of better linearity, a new type of touch mode capacitive pressure sensor named as DDTMCPS is devised, which has a pair of deformable sensing diaphragms. Compared to present touch mode capacitive pressure sensors, the new sensor is characterized by better linearity, and large linear operation range. Such a device also has high sensitivity, and other advantages of normal touch mode capacitive pressure sensor. In the case of such a novel sensor, the second diaphragm served as bottom electrode plays great roles in modifying the deflection of the first diaphragm served as top electrode, furthermore optimizing the performance of touch mode sensors. Silicon fusion bonding technology is advised to fabricate the novel device.     

A new touch mode capacitive pressure sensor with two deformable diaphragms

1　IntroductionCapacitivepressuresensorsareknowntohavehighsensitivity ,robuststructure ,lowsensitivitytoouterenvironmenteffectsandnoturn ontemperaturedrift.However ,largenonlinearityisthedrawbackofsuchdevicesduetotheinverserelationbetweenca pacitanceandspacingbetweentwoelectrodes.Muchefforthasbeenmadetoimprovethelinearityofca pacitivepressuresensors .Amongthoseattempts ,touchmodecapacitivepressuresensorisamoresuc cessfuldesignforinthatnotonlygoodlinearityisgotten ,butalsolargeopera tingpressur…     

Vacuum-sealed silicon micromachined pressure sensors

Considerable progress in silicon pressure sensors has been made in recent years. This paper discusses three types of vacuum-sealed silicon micromachined pressure sensors that represent the present state of the art in this important area. The devices are a capacitive vacuum sensor, a surface-micromachined microdiaphragm pressure sensor, and a resonant pressure sensor. Vacuum sealing for these devices is accomplished using anodic bonding, films deposited using low-pressure chemical vapor deposition, and thermal out-diffusion of hydrogen, respectively. These sensors emphasize high sensitivity, small size, and excellent stability, respectively. The silicon-diaphragm vacuum sensor uses electrostatic force balancing to achieve a wide pressure measurement range     

Versatile Ion-Gel Fibrous Membrane for Energy-Harvesting Iontronic Skin

Developing versatile and high sensitivity sensors is beneficial for promoting flexible electronic devices and human-machine interactive systems. Researchers are working on the exploration of various active sensing materials toward broad detection, multifunction, and low-power consumption. Here, a versatile ion-gel fibrous membrane is presented by electrospinning technology and utilized to construct capacitive sensors and triboelectric nanogenerator (TENG). The iontronic capacitive sensor exhibits inherently favorable sensitivity and repeatability, which retains long-term stability after 5000 cycles. The capacitive sensor can also detect a clear pulse waveform at the human wrist and enable the mapping of pressure distribution by a capacitive sensory matrix. For the iontronic TENG, the maximum peak power is 54.56 µW and can be used to power commercial electronics. In addition, the prepared iontronic TENG array can achieve interactive, rapidly responsive, and accurate dynamic monitoring, which broadens the exploration to direct and effective sensory devices. The versatile ion-gel fibrous membrane is promising to provide an outstanding approach for physiological detection, biomechanical energy harvesting, human-machine interaction, and self-powered monitoring systems.     

A 16-channel capacitance-to-period converter for capacitive sensor applications

An electronic system able to read out arrays of up to sixteen different capacitive type sensors is presented. The output signal of the readout is a square wave signal, with oscillation period linearly modulated by the respective sensor capacitance under measurement. Components such as charge/discharge current control unit, a multiplexing unit and a bandgap voltage reference are integrated on chip, to obtain a stable and linear readout system for multiple sensors of variable types and capacitance ranges. The ASIC was designed and fabricated in AMS 0.35???m CMOS technology and was hosted on a PCB together with a supervising microcontroller, which is programmed to produce ratiometric measurements using reference capacitances to minimise parasitic effects. Finally, a USB interface undertakes the task of communicating the results to a personal computer. Characterization of the system was performed using (a) discrete capacitances and (b) capacitive pressure sensors. The system was evaluated in a capacitance range of 10?C140?pF exhibiting high linearity (r?=?0.9954) with sensitivity of 0.062???s/pF when tested using in-house made capacitive pressure sensors.     

A single-electrode capacitive sensor using incremental delta–sigma architecture

This paper presents a single-electrode capacitive sensor using a single-bit second-order incremental delta–sigma architecture. In order to achieve high accuracy in this capacitance-to-digital converter (CDC), the shielding signal and the digitally controlled offset capacitors are used in combination with the delta–sigma CDC. The designed sensor is suitable for capacitive transducers for ±10 pF input range with sub-fF resolution.     

A new 0.35 μm CMOS electronic interface for wide range floating capacitive and grounded/floating resistive sensor applications

In this paper we propose a novel interface circuit suitable for the read-out of both wide range floating capacitive and grounded/floating resistive sensors. This solution, employing only two Operational Amplifiers (OAs) as active blocks and some passive components, is based on a square-wave oscillating circuit topology which, instead of a voltage integration typically performed by other solutions in the literature, operates a voltage differentiation. Therefore, the proposed circuit, performing an impedance-to-period (Z–T) conversion, results to be suitable as first analog front-end for both wide variation capacitive (e.g., relative humidity) and resistive (e.g., gas) sensors. Its sensitivity and dynamic range can be easily set through external passive components. Preliminary experimental measurements, which have characterized and validated this solution, have been conducted through a suitable prototype PCB fabricated with discrete commercial components. Then, the proposed interface has been also designed at transistor level, in a standard CMOS technology (AMS 0.35 um), developing a single-chip integrated circuit with low-voltage (1.8 V, single supply) low-power (about 350 μW) characteristics in a very small silicon area (lower than 0.6 mm²) which results to be suitable for sensor array configurations and portable applications. Further experimental results, achieved utilizing commercial sample resistors and capacitors to emulate sensor behavior, have shown a linear trend and a satisfactory accuracy in the evaluation of floating capacitive (in the range 10 pF–1 μF), grounded resistive (in the range 150 kΩ–1.5 MΩ) and floating resistive (in the range 10 MΩ–1 GΩ) variations, also when compared to other solutions presented in the literature. The satisfactory interface behavior has been also confirmed by the measurement of both relative humidity through the commercial sensor Honeywell HCH-1000 (capacitive) and carbon monoxide CO through the commercial air quality sensor FIGARO TGS-2600 (resistive).     

Highly Adaptive Transducer Interface Circuit for Multiparameter Microsystems

A reconfigurable transducer interface circuit that combines the communication and signal conditioning necessary to link a variety of sensors and actuators to a microsystem controller is reported. The adaptive readout circuitry supports high-resolution signal acquisition from capacitive, resistive, voltage and current mode sensors with programmable control of gain and offset to match sensor range and sensitivity. The chip accommodates sensor self test and self calibration and supports several power management schemes. It provides digital and analog outputs to control actuators and a standard interface to peripheral components. The 2.2times2.2 mm CMOS chip was fabricated in 0.5-mum, 3-metal, 2-poly process, dissipates ~50 muW at 3.3 V in a typical multisensor application utilizing periodic sleep mode, and can read out a wide range of sensors with high sensitivity. A prototype microsystem with a microcontroller and MEMS pressure, humidity, and temperature sensors has been implemented to characterize interface chip performance     

Rational Design of Capacitive Pressure Sensors Based on Pyramidal Microstructures for Specialized Monitoring of Biosignals

There is an increasing demand for specialized pressure sensors in various applications. Previously, capacitive pressure sensors have been shown to have wide versatility in use, with a high degree of potential tuning possible through manipulating the geometry or material selection of the dielectric layer. However, in order to make sensors that are tunable and predictable, the design and fabrication method first needs to be developed. Presented here is an improved fabrication method to achieve tunable, consistent, and reproducible pressure sensors by using a pyramid microstructured dielectric layer along with a lamination layer. The as‐produced sensor performance is able to match predicted trends. Further, a simple model based on this system is developed and its efficacy is experimentally confirmed. Then, the model to predict a wide range of material and microstructure geometric properties prior to device fabrication is used to provide trends on sensor performance. Finally, it is demonstrated that the new method can be used to targetedly design a pressure sensor for a specific application—in vitro pulse sensing.     

平面电容传感器液位检测系统设计

为了对高度小于100mm的液位进行非接触式测量,采用液位变化改变平面电容边缘电场参量的方法,对平面电容传感器的工作原理进行了理论分析,研究了平面电容传感器的结构参量对其灵敏度、穿透深度的影响,并对传感器结构参量进行了优化, 基于平面电容传感器, 设计了非接触式低液位检测系统,通过对纯净水、洗洁精溶液和墨汁的实验验证,取得了0mm~100mm范围的液位测量数据。结果表明,该检测系统工作稳定,具有线性输出,重复性误差约为±0.28%,数据修正前的测量误差小于7.8%。这一结果对非接触式较低液位的检测是有帮助的。     

A square-diaphragm piezoresistive pressure sensor with arectangular central boss for low-pressure ranges

Describes the theory and experimental data for a piezoresistive low-pressure sensor featuring a variety of advantages. The objective of this development was a sensor with high sensitivity, high overload range, and good linearity. In comparison to familiar sensor types, the sensor developed for the pressure range of 10 kPa exhibits an excellent sensitivity of 35 mV/V FSO (full scale output) and nonlinearity <±0.05%. The sensor's theoretical performance was confirmed by measurements on manufactured pressure sensors     

一种具有较大电容动态测量范围的接口电路

针对应用广泛的电容式传感器信号采集问题,提出了一种具有较大电容动态测量范围的高精度电容式传感器接口电路。该接口电路包括一个电容式有源电桥,以及用于将电容直接转换为频率的张弛振荡器,电路的频率输出用于确定微湿度传感器的响应特性。在基于薄膜的电容湿度传感器上进行了测试,实验结果表明,相比现有的类似电路设计,提出电路的结构更加简单且具有更大的电容测量范围和较高的精度,在1 p-600 p测量范围内的精度（误差百分比）<-2.14%,接口电路灵敏度为4.91 Hz/ppm,且输出频率与电容变化成线性关系。     

A fingerprint sensor based on the feedback capacitive sensingscheme

This paper introduces a single-chip, 200×200-element sensor array implemented in a standard two-metal digital CMOS technology. The sensor is able to grab the fingerprint pattern without any use of optical and mechanical adaptors. Using this integrated sensor, the fingerprint is captured at a rate of 10 F/s by pressing the finger skin onto the chip surface. The fingerprint pattern is sampled by capacitive sensors that detect the electric field variation induced by the skin surface. Several design issues regarding the capacitive sensing problem are reported and the feedback capacitive sensing scheme (FCS) is introduced. More specifically, the problem of the charge injection in MOS switches has been revisited for charge amplifier design     

Fiber-optic current and voltage sensors using a Bi12GeO20single crystal

By using Faraday and Pockels' effects of a Bi12GeO20(BGO) single crystal, two kinds of fiber-optic sensors for electric current and voltage were tentatively fabricated. The optimum design of these sensors and their performances were investigated. It was verified that the BGO crystal is very available for either of the current and voltage sensors with regard to their sensitivity and stability. As for the experimental results, the minimum detectable magnetic field of 10^-2Oe and the temperature dependence within ±2 percent in the temperature range of -25 to 85°C was obtained for the current sensor, while for the voltage sensor the sensitivity of 10^-3V and the temperature dependence within ± 0.5 percent was in the same temperature range.     

Design of an integrated low-noise read-out system for DNA capacitive sensors

This paper presents an electronic system for a fast DNA label-less detection. The sensitivity of the capacitive sensor in use is improved by depositing an insulating self-assembled monolayer (SAM) over the golden electrodes. The capacitance shift due to the hybridization effect is monitored by means of a charge-sensitive amplifier and digitalized by means of a comparator and a counter. The read-out solution demonstrates the ability to identify a 0.01% variation on the capacitive value of the sensor. Results from measurements with the optimized sensor show the reliability of the electronics. The investigated solution is suitable for monolithic systems or for a micro-fabricated array of sensors. An example of the integrated front-end is described and performances and noise evaluation are reported here.     

A Precise Capacitance-to-Pulse Width Converter for Integrated Sensors

This work describes a novel approach for interfacing capacitive sensors in the sub-pF range. The system generates a PWM signal with a linear relationship between the pulse duration and the sensor capacitance. The circuit exhibits intrinsic low sensitivity to temperature and process variations and is therefore an interesting solution when extremely wide operating temperature ranges are required. A detailed analysis of the noise characteristics, aimed to give indications about the circuit optimisation, is presented. The interface has been designed using the 0.35 μm BCD6 process of STMicroelectronics and tested by means of electrical simulations.     

MEMS高精度电容读出电路的单芯片集成研究

MEMS电容式传感器的迅速发展为后续集成化读出电路的设计提出了巨大挑战.系统地分析了制约微传感器高精度电容读出电路设计的主要因素,回顾了目前主要的几种读出电路结构,阐述了这些电路的基本原理,并对影响电路分辨率的主要设计参数进行了分析和对比,最后探讨了电容式读出电路设计的发展趋势.     

Lightweight,Superelastic Boron Nitride/Polydimethylsiloxane Foam as Air Dielectric Substitute for Multifunctional Capacitive Sensor Applications

Porous polymeric foams as dielectric layer for highly sensitive capacitive based pressure sensors have been extensively explored owing to their excellent flexibility and elasticity. Despite intensive efforts, most of previously reported porous polymer foams still suffer from difficulty in further lowering the attainable density limit of ≈0.1 g cm^?3 while retaining high sensitivity and compressibility due to the limitations on existing fabrication techniques and materials. Herein, utilizing 3D interconnected networks of few‐layer hexagonal boron nitride foams (h‐BNFs) as supporting frameworks, lightweight and highly porous BN/polydimethylsiloxane composite foams (BNF@PDMS) with densities reaching as low as 15 mg cm^?3 and permittivity close to that of air are fabricated. This is the lightest PDMS‐based foam reported to date. Owing to the synergistic effects between BN and PDMS, these lightweight composite foams possess excellent mechanical resilience, extremely high compressibility (up to 95% strain), good cyclic performance, and superelasticity. Being electrically nonconductive, the potential application of BNF@PDMS as a dielectric layer for capacitive sensors is further demonstrated. Remarkably, the as‐fabricated device can perform multiple sensing functions such as noncontact touch sensor, environmental monitoring sensor, and high sensitivity pressure sensor that can detect extremely low pressures of below 1 Pa.     

A Soft Resistive Acoustic Sensor Based on Suspended Standing Nanowire Membranes with Point Crack Design

An artificial basilar membrane (ABM) is an acoustic transducer that mimics the mechanical frequency selectivity of the real basilar membrane, which has the potential to revolutionize current cochlear implant technology. While such ABMs can be potentially realized using piezoelectric, triboelectric, and capacitive transduction methods, it remains notoriously difficult to achieve resistive ABM due to the poor frequency discrimination of resistive‐type materials. Here, a point crack technology on noncracking vertically aligned gold nanowire (V‐AuNW) films is reported, which allows for designing soft acoustic sensors with electric signals in good agreement with vibrometer output—a capability not achieved with corresponding bulk cracking system. The strategy can lead to soft microphones for music recognition comparable to the conventional microphone. Moreover, a soft resistive ABM is demonstrated by integrating eight nanowire‐based sensor strips on a soft trapezoid frame. The wearable ABM exhibits high‐frequency selectivity in the range of 319–1951 Hz and high sensitivity of 0.48–4.26 Pa^?1. The simple yet efficient fabrication in conjunction with programmable crack design indicates the promise of the methodology for a wide range of applications in future wearable voice recognition devices, cochlea implants, and human–machine interfaces.     

飞秒激光制备光纤微孔传感器

为了实现高精度、低成本的液体折射率测量,采用飞秒激光水辅助微加工技术,制备出一种基于微孔结构的单模光纤液体折射率传感器.研究了传感器的传输损耗与孔内液体折射率及微孔长度的关系,利用射线理论分析了传感的机理,讨论了温度对传感器性能的影响.结果表明,该传感器在折射率1.333～1.413区间具有良好的线性响应,灵敏度达到157.48dB/RIU,且不易受温度串扰.该传感器具有结构紧凑、制备简单、高灵敏度、温度不敏感和低成本等优点,在生物化学测量领域中有着广泛的应用前景.