Sensors based on the detection of small resistance variations are universally recognized as piezoresistive. Being one of the simplest, most common and most investigated classes of sensors, continuous efforts are focused on creating improved devices with higher performance that can be used in many commercial and non–commercial applications (e.g. evaluation of strain, pressure, acceleration, force etc.). Consequently, despite the fact that more than 150 years have passed since the discovery of the piezoresistive effect in some classes of metals and semiconductors, the development of such sensors remains interesting and topical. Moreover, with the advent of second–generation robotics, research on piezoresistive sensors has undergone a massive increase. This paper aims to be a short, self–consistent vademecum which would be useful to researchers and engineers, since it focuses on the fundamentals of theory, materials, and readout–circuit design pertinent to the most recent developments in the field of piezoresistive sensors.

Theory, technology and applications of piezoresistive sensors: A review

Over the past four decades, the field of silicon piezoresistive pressure sensors has undergone a major revolution in terms of design methodology and fabrication processes. Cutting edge fabrication technologies have resulted in improved precision in key factors like dimensions of diaphragm and placement of piezoresistors. Considering the unique nature of each sensor and the trade-offs in design, it is not feasible to follow a standard design approach. Thus, it is useful to derive the specific design from a number of important factors to arrive at the `ideal' design. In this paper, we critically review and analyze the various design considerations and principles for silicon piezoresistive pressure sensor. We also report the effect of these considerations on the sensor output taking help of various CAD tools. Keeping in view the accuracy of state-of-the-art fabrication tools and the stringent demands of the present day market, it has become important to include many of these design aspects. Modelling using analytical expressions for thin plates has also been looked into as it gives a quick guideline and estimation of critical parameters before detailed finite element method analysis. Wherever possible, fabrication imperfections and their effects have been discussed. Dependency of piezoresistive coefficients on temperature and doping concentration, the effect of clamping condition of diaphragms and fabrication using wet bulk micromachining is also analyzed. Silicon-on-insulator based sensors along with innovative design strategies, and future trends have also been discussed. This paper will serve as a quick and comprehensive guide for pressure sensor developers.

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Erratum to: Design principles and considerations for the `ideal' silicon piezoresistive pressure sensor: a focused review

Pressures in the intracranial, intraocular and intravascular spaces are clinically useful for the diagnosis and management of traumatic brain injury, glaucoma and hypertension, respectively Conventional devices for measuring these pressures require surgical extraction after a relevant operational time frame Bioresorbable sensors, by contrast, eliminate this requirement, thereby minimizing the risk of infection, decreasing the costs of care and reducing distress and pain for the patient However, the operational lifetimes of bioresorbable pressure sensors available at present fall short of many clinical needs Here, we present materials, device structures and fabrication procedures for bioresorbable pressure sensors with lifetimes exceeding those of previous reports by at least tenfold We demonstrate measurement accuracies that compare favourably to those of the most sophisticated clinical standards for non-resorbable devices by monitoring intracranial pressures in rats for 25 days Assessments of the biodistribution of the constituent materials, complete blood counts, blood chemistry and magnetic resonance imaging compatibility confirm the biodegradability and clinical utility of the device Our findings establish routes for the design and fabrication of bioresorbable pressure monitors that meet requirements for clinical use

Bioresorbable pressure sensors protected with thermally grown silicon dioxide for the monitoring of chronic diseases and healing processes

To obtain ideal sensing materials with nearly zero temperature coefficient resistance (TCR) for self-temperature-compensated pressure sensors, we proposed an Incipient Network Conformal Growth (INCG) technology to prepare hybrid and elastic porous materials: the nanoparticles (NPs) are first dispersed in solvent to form an incipient network, another component is then introduced to coat the incipient network conformally via wet chemical route. The conformal coatings not only endow NPs with high stability but also offer them additional structural elasticity, meeting requirements for future generations of portable, compressive and flexible devices. The resultant polypyrrole/silver coaxial nanowire hybrid aero-sponges prepared via INCG technology have been processed into a piezoresistive sensor with highly sensing stability (low TCR 0.86 × 10–3/°C), sensitivity (0.33 kPa–1), short response time (1 ms), minimum detectable pressure (4.93 Pa) after suffering repeated stimuli, temperature change and electric heat...

Polypyrrole/Silver Coaxial Nanowire Aero-Sponges for Temperature-Independent Stress Sensing and Stress-Triggered Joule Heating

Searching strain sensitive materials for electronic skin is of crucial significance because of the restrictions of current materials such as poor electrical conductivity, large energy consumption, complex manufacturing process, and high cost. Here, we report a flexible strain sensor based on the Zr55Cu30Ni5Al10 metallic glass thin film which we name metallic glass skin. The metallic glass skin, synthesized by ion beam deposition, exhibits piezoresistance effects with a gauge factor of around 2.86, a large detectable strain range (∼1% or 180° bending angle), and good conductivity. Compared to other e-skin materials, the temperature coefficient of resistance of the metallic glass skin is extremely low (9.04 × 10−6 K−1), which is essential for the reduction in thermal drift. In addition, the metallic glass skin exhibits distinct antibacterial behavior desired for medical applications, also excellent reproducibility and repeatability (over 1000 times), nearly perfect linearity, low manufacturing cost, and neg...

Flexible strain sensors with high performance based on metallic glass thin film

For the purposes of pressure measurement at high temperature in oil drilling industry as well as in other industrial measurement and control systems, the strain gauge chip of piezoresistive pressure sensor is designed based on separation by implanted oxygen (SIMOX) SOI (silicon on insulator) technology, and then fabricated in the micro-machining work bay. Some kinds of sensor mechanical structures are designed for different customers and conditions. The thermal coefficients of expansion (TCE) mismatches between different materials within the high-pressure sensor system are investigated. The sensor is fabricated successfully by using high temperature packaging process. The temperature coefficient of sensitivity (TCS) and temperature coefficient of offset (TCO) compensation circuitry is demonstrated. Based on experimental data, the sensor is tested with high accuracy and good stability.

Fabrication and temperature coefficient compensation technology of low cost high temperature pressure sensor

The present invention aims at providing one kind of silicon chip/glass ring bonding apparatus suitable for mass production. In the apparatus, the electric soldering iron is used as the upper electrode and heating part, is fixed on stainless steel rack and can shift up and down back and forth. The wire connected to the electric soldering iron and the holed steel plate form DC loop via the DC transformer to provide electrostatic field, and the AC power supply of 220 V is used to heat the Pyrex glass ring. The present invention has bonding time as short as 2 min and bonding voltage as low as 160 V, and realize low temperature low voltage fast chip/glass ring bonding.

Silicon chip / glass ring bonding apparatus

The present invention is aimed at providing a method for improving high-temperature-resistant microtype low-cost pressure transducer Said method adopts the following steps: making silicon chip and glass ring be connected together by utilizing electrostatic bonding process, selecting annealed gold wire, thermal compression bonding to implement inner lead bonding; adopting high-temperature adhesive to make the silicon chip/glass ring composite elastic body be cohered in stainless steel fastener, and making the inner fastener be cohered on the stainless steel base, hardening said combined body at room temperature, further hardening said combined body is oven, adopting high-temperature soldering tin wire to make high-temperature wire be soldered on high-temperature circuit board, hardening sensor in high-temperature oven to make it obtain final bond strength, parallel-connecting resistors between red and yellow lines and between red and green lines respectively and series-connecting resistor between red and black lines so as to obtain the invented product

Wang Quan

Papers

Fabrication and temperature coefficient compensation technology of low cost high temperature pressure sensor

Silicon chip / glass ring bonding apparatus

Method for improving high-temp-resistant micro-low cost pressure sensor