Graphene-based Pressure Sensor Research Articles

ELECTROMECHANICAL PRESSURE SENSORS BASED ON GRAPHENE: A REVIEW

Nanotechnology can revolutionize the sensor industry by introducing specific nanomaterials to work as sensing elements. Graphene, a two-dimensional carbon allotrope with exceptional electrical and mechanical properties, has emerged as a promising material for developing high-performance pressure sensors. Graphene-based pressure sensors offer significant advantages over traditional sensors, including high sensitivity, wide dynamic range, fast response time, and flexibility. This paper aims to deliver a review on the fundamental mechanisms underlying graphene-based pressure sensors, which includes piezoresistive, capacitive, and field-effect transistor (FET). Recent advancements in graphene-based pressure sensors have opened up new possibilities in various fields, including healthcare, electronics, and robotics. Here, we will highlight these emerging applications and explore the potential future developments of this technology.

Recent Advances in Graphene-Based Pressure Sensors: A Review

Recent Advances in Graphene-Based Pressure Sensors: A Review

ELECTROMECHANICAL PRESSURE SENSORS BASED ON GRAPHENE: A REVIEW

Objective: This review explores the potential of graphene, a two-dimensional carbon allotrope, in revolutionizing pressure sensors. Graphene's exceptional electrical and mechanical properties enable significant advancements in sensitivity, dynamic range, response time, and flexibility, addressing limitations in traditional sensor technologies. Methods: The study examines the fundamental mechanisms of graphene-based pressure sensors, including piezoresistive, capacitive, and field-effect transistor (FET) mechanisms. A comparative analysis of conventional materials such as piezoelectric, metallic, silicon, and polymer-based materials is conducted to highlight their strengths and limitations. The integration of nanomaterials, particularly graphene, into sensor designs is reviewed, emphasizing their contributions to enhanced sensor performance. Results: Graphene-based sensors demonstrate superior sensitivity and miniaturization capabilities due to their high surface-to-volume ratio, tunable electrical conductivities, and mechanical resilience. Emerging applications in healthcare, electronics, and robotics validate the transformative impact of graphene on sensor technologies. Novelty: This review underscores the unique advantages of graphene over traditional materials, emphasizing its potential to address challenges related to sensitivity, response time, and durability in extreme conditions. Future research directions are proposed to overcome existing limitations and expand the scope of graphene-based sensors across diverse industries.

Preparation of a Vertical Graphene-Based Pressure Sensor Using PECVD at a Low Temperature.

Flexible pressure sensors have received much attention due to their widespread potential applications in electronic skins, health monitoring, and human–machine interfaces. Graphene and its derivatives hold great promise for two-dimensional sensing materials, owing to their superior properties, such as atomically thin, transparent, and flexible structure. The high performance of most graphene-based pressure piezoresistive sensors relies excessively on the preparation of complex, post-growth transfer processes. However, the majority of dielectric substrates cannot hold in high temperatures, which can induce contamination and structural defects. Herein, a credibility strategy is reported for directly growing high-quality vertical graphene (VG) on a flexible and stretchable mica paper dielectric substrate with individual interdigital electrodes in plasma-enhanced chemical vapor deposition (PECVD), which assists in inducing electric field, resulting in a flexible, touchable pressure sensor with low power consumption and portability. Benefitting from its vertically directed graphene microstructure, the graphene-based sensor shows superior properties of high sensitivity (4.84 KPa−1) and a maximum pressure range of 120 KPa, as well as strong stability (5000 cycles), which makes it possible to detect small pulse pressure and provide options for preparation of pressure sensors in the future.

Highly responsive screen-printed asymmetric pressure sensor based on laser-induced graphene

Graphene-based pressure sensors have received extensive attention in wearable devices. However, reliable, low-cost, and large-scale preparation of structurally stable graphene electrodes for flexible pressure sensors is still a challenge. Herein, for the first time, laser-induced graphene (LIG) powder are prepared into screen printing ink, and shape-controllable LIG patterned electrodes can be obtained on various substrates using a facile screen printing process, and a novel asymmetric pressure sensor composed of the resulting screen-printed LIG electrodes has been developed. Benefit from the 3D porous structure of LIG, the as-prepared flexible LIG screen-printed asymmetric pressure sensor has super sensing properties with a high sensitivity of 1.86 kPa−1, low detection limit of about 3.4 Pa, short response time, and long cycle durability. Such excellent sensing performances give our flexible asymmetric LIG screen-printed pressure sensor the ability to realize real-time detection of tiny body physiological movements (such as wrist pulse and pronunciation action). Besides, the integrated sensor array has a multi-touch function. This work could stimulate an appropriate approach to designing shape-controllable LIG screen-printed patterned electrodes on various flexible substrates to adapt the specific needs of fulfilling compatibility and modular integration for potential application prospects in wearable electronics.

Graphene-based pressure sensor and strain sensor for detecting human activities

Wearable pressure sensors and strain sensors with high sensitivity and large working range are essential for detecting human motions. However, fabricating wearable sensors, which are capable of detecting pressure or strain signals, still remains challenging. Herein, two kinds of novel sensors, pressure sensors and strain sensors, are fabricated using the same materials and similar fabrication processes. The sensors are fabricated by soaking cotton in graphene inks so as to avoid high temperature and toxic chemicals caused by reduction compared to traditional graphene oxide inks. The pressure sensor shows excellent performance with high sensitivity (0.12–0.41 kPa−1) and broad working range (0–20 kPa). The strain sensor also has outstanding sensitivity (gauge factor 22.6–83.7) and large working strain of 27%. These two sensors are further demonstrated to show the ability of detecting human activities such as breathing, wrist pulsing, respiration, etc. The low-cost and scalable fabrication along with the good comprehensive performance of the sensors makes them applicable in wearable electronic devices for human health monitoring and movements.

Enhanced-sensitivity and highly flexible stress/strain sensor based on PZT nanowires-modified graphene with wide range carrier mobility

Flexible stress/strain sensors have widespread applications including healthy monitoring systems, smart robotics, and wearable devices. Graphene, a promising carbon material with several excellent properties, is widely used in flexible stress/strain sensors. Creating a graphene-based pressure sensor with improved sensitivity remains highly challenging owing to the difficulty in widening the band gap of graphene. Herein, a novel heterostructural enhanced-sensitivity stress/strain sensor composed of two-dimensional (2D) graphene and one-dimensional (1D) lead zirconate titanate (PZT) nanowires as the sensitivity material, was fabricated. The polarized charges generated by the piezoelectric nanowires under mechanical stress acted as ionized impurities to increase the scattering carriers of graphene, thereby changing its conductivity; additionally, the high piezoelectric property of nanowires provided numerous polarized charges, resulting in increased scattering carriers. Therefore, the as-fabricated device has an enhanced sensitivity of 2.95 × 10−2 kPa−1, which is higher than that of the pure graphene-based pressure sensor. In particular, the fabricated sensor can detect bending strain, such as the bending and straightening of a finger, and the angle of opening a book. Furthermore, the device can record handwritten signals that can be used as indicators of biometric information. Thus, the fabricated device provides a viable and convenient approach for application in multi-functional electronic wearable devices.

Temperature Characteristics of a Pressure Sensor Based on BN/Graphene/BN Heterostructure.

Temperature is a significant factor in the application of graphene-based pressure sensors. The influence of temperature on graphene pressure sensors is twofold: an increase in temperature causes the substrates of graphene pressure sensors to thermally expand, and thus, the graphene membrane is stretched, leading to an increase in the device resistance; an increase in temperature also causes a change in the graphene electrophonon coupling, resulting in a decrease in device resistance. To investigate which effect dominates the influence of temperature on the pressure sensor based on the graphene–boron nitride (BN) heterostructure proposed in our previous work, the temperature characteristics of two BN/graphene/BN heterostructures with and without a microcavity beneath them were analyzed in the temperature range 30–150 °C. Experimental results showed that the resistance of the BN/graphene/BN heterostructure with a microcavity increased with the increase in temperature, and the temperature coefficient was up to 0.25%°C−1, indicating the considerable influence of thermal expansion in such devices. In contrast, with an increase in temperature, the resistance of the BN/graphene/BN heterostructure without a microcavity decreased with a temperature coefficient of −0.16%°C−1. The linearity of the resistance change rate (ΔR/R)–temperature curve of the BN/graphene/BN heterostructure without a microcavity was better than that of the BN/graphene/BN heterostructure with a microcavity. These results indicate that the influence of temperature on the pressure sensors based on BN/graphene/BN heterostructures should be considered, especially for devices with pressure microcavities. BN/graphene/BN heterostructures without microcavities can be used as high-performance temperature sensors.

Fabrication of Low-Cost and Highly Sensitive Graphene-Based Pressure Sensors by Direct Laser Scribing Polydimethylsiloxane.

The cost-effective production of flexible interconnects is a challenge in epidermal electronics. Here we report a low-cost approach for producing and patterning graphene films from polydimethylsiloxane films by direct laser scribing in ambient air. The produced graphene films exhibit high electrical conductivity and excellent mechanical properties and can thus be used directly as a flexible conductive layer without the need for metals. The skinlike pressure sensor with these layers exhibits ultrahigh sensitivity (∼480 kPa-1) while maintaining the fast response/relaxation time (2 μs/3 μs) and excellent cycle stability (>4000 repetitive cycles). Moreover, it can naturally attach to the skin to monitor the wrist pulse. In addition, a 7 × 7 sensor array has been fabricated, which possesses the capability to detect the spatial distribution of pressure. This device has great potential for application in epidermal electronics because of its low cost and high performance.

Static Capacitive Pressure Sensing Using a Single Graphene Drum.

To realize nanomechanical graphene-based pressure sensors, it is beneficial to have a method to electrically readout the static displacement of a suspended graphene membrane. Capacitive readout, typical in micro-electromechanical systems, gets increasingly challenging as one starts shrinking the dimensions of these devices because the expected responsivity of such devices is below 0.1 aF/Pa. To overcome the challenges of detecting small capacitance changes, we design an electrical readout device fabricated on top of an insulating quartz substrate, maximizing the contribution of the suspended membrane to the total capacitance of the device. The capacitance of the drum is further increased by reducing the gap size to 110 nm. Using an external pressure load, we demonstrate the successful detection of capacitance changes of a single graphene drum down to 50 aF, and pressure differences down to 25 mbar.

Highly-Sensitive Graphene-based Flexible Pressure Sensor Platform

In this work, graphene has been utilized as the sensing material for the development of a highly-sensitive flexible pressure sensor platform. It has been demonstrated that a graphene-based pressure sensor platform that is able to measure pressure change of up to 3 psi with a sensitivity of 0.042 psi-1 and a non-linearity of less than 1% has been accomplished. The developed device, which resides on a flexible platform, will be applicable for integration in continuous wearables health-care monitoring system for the measurement of blood pressure.

Recent Advances in Graphene-Based Pressure Sensors

With the promising applications in artificial intelligence systems and wearable health care devices, great efforts have been devoted to develop advanced pressure sensors. Graphene-based materials are promising pressure sensor materials due to the excellent electrical conductivity, outstanding mechanical properties and large surface area. This review summarizes the recent advances and progress in graphene and graphene-based pressure sensors. Perspectives and challenges in this exciting field are also highlighted and discussed.

Graphene "microdrums" on a freestanding perforated thin membrane for high sensitivity MEMS pressure sensors.

We present a microelectromechanical system (MEMS) graphene-based pressure sensor realized by transferring a large area, few-layered graphene on a suspended silicon nitride thin membrane perforated by a periodic array of micro-through-holes. Each through-hole is covered by a circular drum-like graphene layer, namely a graphene "microdrum". The uniqueness of the sensor design is the fact that introducing the through-hole arrays into the supporting nitride membrane allows generating an increased strain in the graphene membrane over the through-hole array by local deformations of the holes under an applied differential pressure. Further reasons contributing to the increased strain in the devised sensitive membrane include larger deflection of the membrane than that of its imperforated counterpart membrane, and direct bulging of the graphene microdrum under an applied pressure. Electromechanical measurements show a gauge factor of 4.4 for the graphene membrane and a sensitivity of 2.8 × 10(-5) mbar(-1) for the pressure sensor with a good linearity over a wide pressure range. The present sensor outperforms most existing MEMS-based small footprint pressure sensors using graphene, silicon, and carbon nanotubes as sensitive materials, due to the high sensitivity.

Piezoresistive effects in controllable defective HFTCVD graphene-based flexible pressure sensor.

In this work, the piezoresistive effects of defective graphene used on a flexible pressure sensor are demonstrated. The graphene used was deposited at substrate temperatures of 750, 850 and 1000 °C using the hot-filament thermal chemical vapor deposition method in which the resultant graphene had different defect densities. Incorporation of the graphene as the sensing materials in sensor device showed that a linear variation in the resistance change with the applied gas pressure was obtained in the range of 0 to 50 kPa. The deposition temperature of the graphene deposited on copper foil using this technique was shown to be capable of tuning the sensitivity of the flexible graphene-based pressure sensor. We found that the sensor performance is strongly dominated by the defect density in the graphene, where graphene with the highest defect density deposited at 750 °C exhibited an almost four-fold sensitivity as compared to that deposited at 1000 °C. This effect is believed to have been contributed by the scattering of charge carriers in the graphene networks through various forms such as from the defects in the graphene lattice itself, tunneling between graphene islands, and tunneling between defect-like structures.

Fabrication of a graphene-based pressure sensor by utilising field emission behavior of carbon nanotubes

In this paper, a miniature graphene-based field emission pressure sensor is reported for the first time, in which carbon nanotubes have been applied as the cathode and reduced graphene oxide sheets have been utilized as the flexible anode. Since, graphene is the thinnest (one atom thick) known structure with a uniform thickness, graphene based membrane is a promising candidate for pressure sensors which allows both high sensitivity and very small chip area, simultaneously. A maximum sensitivity of about 21.9μA/A/Pa is achieved at the bias voltage of 5 V for the fabricated field emission pressure sensor, which is about two orders of magnitude higher than the previously reported graphene based pressure sensors. The fabricated structure has been also used as a graphene based resonator in which emission current is applied to detect the mechanical resonance, efficiently. The measured resonance frequency is measured about 10 MHz, which is shifted to lower frequencies by increasing the ambient pressure. The measured sensitivity, for the resonant operation mode, is about 11.32 Hz/Pa (S = Δf/ΔP). Owing to the inherent low mass of graphene, the presented structure can be entitled as a promising resonant pressure sensor.

Graphene-based pressure nano-sensors

We perform atomistic simulations to study the failure behavior of graphene-based pressure sensor, which is made of a graphene nanoflake suspended over a well in a silicon-carbide substrate and clamped on its surrounding edge by the covalent bonds between the graphene flake and the substrate. Two distinct types of mechanical failure are identified: the first one is characterized by complete detachment of the graphene nanoflake from the silicon-carbide substrate via breaking the covalent bonds between the carbon atoms of the graphene flake and the silicon atoms of the substrate; the second type is characterized by the rupture of the graphene nanoflake via breaking the carbon-carbon bonds within the graphene. The type of mechanical failure is determined by the clamped area between the graphene flake and the substrate. The failure pressure can be tuned by changing the clamped area and the well radius. A model is proposed to explain the transition between the two types of failure mode. The present work provides a quantitative framework for the design of graphene-based pressure sensors.