Flexible and Transparent Pressure Sensor Based on CNTs Film Microstructure

Detection Range ◽

Electronic Skin ◽

Film Microstructure ◽

Abstract In recent years, capacitive flexible pressure sensors have been widely studied in electronic skin and wearable devices. The traditional capacitive pressure sensor has a higher production cost due to micro-nano machining technology such as lithography. This paper presents a flexible transparent capacitive pressure sensor based on a PDMS/CNT composite electrode, simple, transparent, flexible, and arrays without lithography. The sensitivity of the device has been tested to 0.0018 kpa -1 with a detection range of 0-30 kPa. The sensor is capable of rapidly detecting different pressures and remains stable after 100 load-unload tests.

Flexible Pressure Sensors with a Wide Detection Range Based on Self-Assembled Polystyrene Microspheres

Sensors ◽

10.3390/s19235194 ◽

2019 ◽

Vol 19 (23) ◽

pp. 5194

Author(s):

Wufan Chen ◽

Bingwei Wang ◽

Qianbing Zhu ◽

Xin Yan

Keyword(s):

Pressure Sensor ◽

Pressure Sensors ◽

Wearable Devices ◽

Large Area ◽

Polystyrene Microsphere ◽

Detection Range ◽

Electronic Skin ◽

Self Assembled ◽

Flexible Pressure Sensors ◽

Wide Pressure

Flexible pressure sensors are important components of electronic skin and flexible wearable devices. Most existing piezoresistive flexible pressure sensors have obtained high sensitivities, however, they have relatively small pressure detection ranges. Here, we report flexible pressure sensors with a wide detection range using polydimethylsiloxane (PDMS) as the substrate, carbon nanotube films as the electrode material, and self-assembled polystyrene microsphere film as the microstructure layer. The obtained pressure sensor had a sandwich structure, and had a wide pressure detection range (from 4 kPa to 270 kPa), a sensitivity of 2.49 kPa−1, and a response time of tens of milliseconds. Two hundred load–unload cycles indicated that the device had good stability. In addition, the sensor was obtained by large-area fabrication with a low power consumption. This pressure sensor is expected to be widely used in applications such as electronic skin and flexible wearable devices.

A Highly Sensitive and Flexible Capacitive Pressure Sensor Based on a Porous Three-Dimensional PDMS/Microsphere Composite

Polymers ◽

10.3390/polym12061412 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1412 ◽

Cited By ~ 2

Author(s):

Young Jung ◽

Wookjin Lee ◽

Kyungkuk Jung ◽

Byunggeon Park ◽

Jinhyoung Park ◽

...

Keyword(s):

Pressure Sensor ◽

Sacrificial Layer ◽

Three Dimensional ◽

Pressure Sensors ◽

Mechanical Stimuli ◽

Highly Sensitive ◽

Flexible Pressure Sensors ◽

Fast Rise ◽

Better Than

In recent times, polymer-based flexible pressure sensors have been attracting a lot of attention because of their various applications. A highly sensitive and flexible sensor is suggested, capable of being attached to the human body, based on a three-dimensional dielectric elastomeric structure of polydimethylsiloxane (PDMS) and microsphere composite. This sensor has maximal porosity due to macropores created by sacrificial layer grains and micropores generated by microspheres pre-mixed with PDMS, allowing it to operate at a wider pressure range (~150 kPa) while maintaining a sensitivity (of 0.124 kPa−1 in a range of 0~15 kPa) better than in previous studies. The maximized pores can cause deformation in the structure, allowing for the detection of small changes in pressure. In addition to exhibiting a fast rise time (~167 ms) and fall time (~117 ms), as well as excellent reproducibility, the fabricated pressure sensor exhibits reliability in its response to repeated mechanical stimuli (2.5 kPa, 1000 cycles). As an application, we develop a wearable device for monitoring repeated tiny motions, such as the pulse on the human neck and swallowing at the Adam’s apple. This sensory device is also used to detect movements in the index finger and to monitor an insole system in real-time.

Ultra-Sensitive Flexible Pressure Sensor Based on Microstructured Electrode

Sensors ◽

10.3390/s20020371 ◽

2020 ◽

Vol 20 (2) ◽

pp. 371 ◽

Cited By ~ 5

Author(s):

Mengmeng Li ◽

Jiaming Liang ◽

Xudong Wang ◽

Min Zhang

Keyword(s):

Pressure Sensor ◽

Dielectric Layer ◽

Pressure Sensors ◽

High Sensitivity ◽

Capacitive Sensor ◽

Duty Ratio ◽

Element Analysis ◽

Sequential Coupling ◽

Flexible pressure sensors with a high sensitivity in the lower zone of a subtle-pressure regime has shown great potential in the fields of electronic skin, human–computer interaction, wearable devices, intelligent prosthesis, and medical health. Adding microstructures on the dielectric layer on a capacitive pressure sensor has become a common and effective approach to enhance the performance of flexible pressure sensors. Here, we propose a method to further dramatically increase the sensitivity by adding elastic pyramidal microstructures on one side of the electrode and using a thin layer of a dielectric in a capacitive sensor. The sensitivity of the proposed device has been improved from 3.1 to 70.6 kPa−1 compared to capacitive sensors having pyramidal microstructures in the same dimension on the dielectric layer. Moreover, a detection limit of 1 Pa was achieved. The finite element analysis performed based on electromechanical sequential coupling simulation for hyperelastic materials indicates that the microstructures on electrode are critical to achieve high sensitivity. The influence of the duty ratio of the micro-pyramids on the sensitivity of the sensor is analyzed by both simulation and experiment. The durability and robustness of the device was also demonstrated by pressure testing for 2000 cycles.

Carbonized Cotton Fabric-Based Flexible Capacitive Pressure Sensor Using a Porous Dielectric Layer with Tilted Air Gaps

Sensors ◽

10.3390/s21113895 ◽

2021 ◽

Vol 21 (11) ◽

pp. 3895

Author(s):

Yelin Ko ◽

Chi Cuong Vu ◽

Jooyong Kim

Keyword(s):

Cotton Fabric ◽

Pressure Sensor ◽

Low Cost ◽

Pressure Sensors ◽

Wearable Electronics ◽

Detection Range ◽

Air Gaps ◽

Wide Range ◽

Knitted Structure

Flexible and wearable pressure sensors have attracted significant attention owing to their roles in healthcare monitoring and human–machine interfaces. In this study, we introduce a wide-range, highly sensitive, stable, reversible, and biocompatible pressure sensor based on a porous Ecoflex with tilted air-gap-structured and carbonized cotton fabric (CCF) electrodes. The knitted structure of electrodes demonstrated the effectiveness of the proposed sensor in enhancing the pressure-sensing performance in comparison to a woven structure due to the inherent properties of naturally generated space. In addition, the presence of tilted air gaps in the porous elastomer provided high deformability, thereby significantly improving the sensor sensitivity compared to other dielectric structures that have no or vertical air gaps. The combination of knitted CCF electrodes and the porous dielectric with tilted air gaps achieved a sensitivity of 24.5 × 10−3 kPa−1 at 100 kPa, along with a wide detection range (1 MPa). It is also noteworthy that this novel method is low-cost, facile, scalable, and ecofriendly. Finally, the proposed sensor integrated into a smart glove detected human motions of grasping water cups, thus demonstrating its potential applications in wearable electronics.

High sensitivity and broad detection range flexible capacitive pressure sensor based on rGO cotton fiber for human motion detection

Smart Materials and Structures ◽

10.1088/1361-665x/ac3c07 ◽

2021 ◽

Author(s):

Rongliang Zheng ◽

Youyuan Wang ◽

Zhanxi Zhang ◽

Yanfang Zhang ◽

Jinzhan Liu

Keyword(s):

Pressure Sensor ◽

Cotton Fiber ◽

Pressure Sensors ◽

High Sensitivity ◽

Human Motion ◽

Superior Performance ◽

Joint Movement ◽

Process Technology ◽

Abstract Recently, flexible pressure sensors have attracted considerable interest in electronic skins, wearable devices, intelligent robots and biomedical diagnostics. However, the design of high sensitivity flexible pressure sensors often relies on expensive materials and complex process technology, which greatly limit their popularity and applications. Even worse, chemical-based sensors are poorly biocompatible and harmful to the environment. Here, we developed a flexible capacitive pressure sensor based on reduced graphene oxide (rGO) cotton fiber by a simple and low-cost preparation process. The environmentally friendly sensor exhibited a comprehensive performance with not only ultra-high sensitivity (up to 15.84 kPa-1) and a broad sensing range (0-500 kPa), but also excellent repeatability (over 400 cycles), low hysteresis (≤11.6%), low detection limit (<0.1 kPa) and wide frequency availability (sensitivity from 19.71 kPa-1 to 11.24 kPa-1, frequency from 100 Hz to 10 kHz). Based on its superior performance, the proposed sensor can detect various external stimuli (vertical stress, bending and airflow) and has been successfully applied for facial expression recognition, breathing detection, joint movement and walking detection, showing great potential for application in artificial electronic skin and wearable healthcare devices.

A theoretical model of flexible capacitive pressure sensor with microstructured electrode for highly sensitive electronic skin

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/ac34a9 ◽

2021 ◽

Author(s):

Weidong Yang ◽

Wenxuan Ding ◽

Menglong Liu ◽

Jun Yang ◽

Mao Li

Keyword(s):

Pressure Sensor ◽

Electromechanical Coupling ◽

Present Model ◽

Pressure Sensors ◽

Compressive Force ◽

Contact Radius ◽

Electronic Skin ◽

Highly Sensitive ◽

Theory Framework

Abstract Electronic skin (E-skin) has attracted much attention in smart wearables, prosthetics, and robotics. The capacitive-type pressure sensor is generally regarded as one good option to design tactile sensing devices owing to its superior sensitivity in low-pressure region, fast response time and convenient manufacturing. Introducing microstructures on electrode surface is an effective approach to achieve highly sensitive capacitive pressure sensors. In this work, an electromechanical model is proposed to build the relationship between capacitance change and compressive force. The present model can predict the sensitivity of capacitive pressure sensor with microstructured electrodes, where each cellular microstructure is modeled using the contact mechanics theory. It is the first time in the literature that based on Hertz theory framework, one rigorous electromechanical theory framework is established to model flexible capacitive pressure sensor, and the model can be extended to other microstructures, such as micro-pyramid, micro-pillar, and micro-dome array. The validation indicates that the analytical results well agree with the experimental data from our previous work and other literatures. Moreover, the present model can well capture the sensitivity of pressure sensor on the beginning range of small pressure. The sensitivity on this range is the most significant for the E-skin due to its robust linearity for one pressure sensor. Besides, we analyzed the compressive force-displacement relationship, the compressive force-contact radius relationship and the influences of the geometrical and material parameters on the electromechanical coupling effect. The results show that the height and the Young’s modulus of the soft dielectric layer are regarded as the dominant influencing factors in the sensitivity of capacitive pressure sensors.

Printed and Flexible Capacitive Pressure Sensor with Carbon Nanotubes based Composite Dielectric Layer

Micromachines ◽

10.3390/mi10110715 ◽

2019 ◽

Vol 10 (11) ◽

pp. 715 ◽

Cited By ~ 1

Author(s):

Zhenxin Guo ◽

Lixin Mo ◽

Yu Ding ◽

Qingqing Zhang ◽

Xiangyou Meng ◽

...

Keyword(s):

Artificial Intelligence ◽

Carbon Nanotubes ◽

Aspect Ratio ◽

Pressure Sensor ◽

Dielectric Layer ◽

Pressure Sensors ◽

Weight Fraction ◽

Flexible Pressure Sensor ◽

Flexible pressure sensors have attracted tremendous attention from researchers for their widely applications in tactile artificial intelligence, electric skin, disease diagnosis, and healthcare monitoring. Obtaining flexible pressure sensors with high sensitivity in a low cost and convenient way remains a huge challenge. In this paper, the composite dielectric layer based on the mixture of carbon nanotubes (CNTs) with different aspect ratios and polydimethylsiloxane (PDMS) was employed in flexible capacitive pressure sensor to increase its sensitivity. In addition, the screen printing instead of traditional etching based methods was used to prepare the electrodes array of the sensor. The results showed that the aspect ratio and weight fraction of the CNTs play an important role in improving the sensitivity of the printed capacitive pressure sensor. The prepared capacitive sensor with the CNTs/PDMS composite dielectric layer demonstrated a maximum sensitivity of 2.9 kPa−1 in the pressure range of 0–450 Pa, by using the CNTs with an aspect ratio of 1250–3750 and the weight fraction of 3.75%. The mechanism study revealed that the increase of the sensitivity of the pressure sensor should be attributed to the relative permittivity increase of the composite dielectric layer under pressure. Meanwhile, the printed 3 × 3 and 10 × 10 sensor arrays showed excellent spatial resolution and uniformity when they were applied to measure the pressure distribution. For further applications, the flexible pressure sensor was integrated on an adhesive bandage to detect the finger bending, as well as used to create Morse code by knocking the sensor to change their capacitance curves. The printed and flexible pressure sensor in this study might be a good candidate for the development of tactile artificial intelligence, intelligent medical diagnosis systems and wearable electronics.

Development of circuit solution and design of capacitive pressure sensor array for applied robotics

Robotics and Technical Cybernetics ◽

10.31776/rtcj.8406 ◽

2020 ◽

Vol 8 (4) ◽

pp. 296-307

Author(s):

Konstantin Krestovnikov ◽

Aleksei Erashov ◽

Аleksandr Bykov

Keyword(s):

Pressure Sensor ◽

Output Signal ◽

Sensor Array ◽

Applied Pressure ◽

Pressure Sensors ◽

Fine Tuning ◽

Cell Parameters ◽

Linear Pattern ◽

Sensor Structure

This paper presents development of pressure sensor array with capacitance-type unit sensors, with scalable number of cells. Different assemblies of unit pressure sensors and their arrays were considered, their characteristics and fabrication methods were investigated. The structure of primary pressure transducer (PPT) array was presented; its operating principle of array was illustrated, calculated reference ratios were derived. The interface circuit, allowing to transform the changes in the primary transducer capacitance into voltage level variations, was proposed. A prototype sensor was implemented; the dependency of output signal power from the applied force was empirically obtained. In the range under 30 N it exhibited a linear pattern. The sensitivity of the array cells to the applied pressure is in the range 134.56..160.35. The measured drift of the output signals from the array cells after 10,000 loading cycles was 1.39%. For developed prototype of the pressure sensor array, based on the experimental data, the average signal-to-noise ratio over the cells was calculated, and equaled 63.47 dB. The proposed prototype was fabricated of easily available materials. It is relatively inexpensive and requires no fine-tuning of each individual cell. Capacitance-type operation type, compared to piezoresistive one, ensures greater stability of the output signal. The scalability and adjustability of cell parameters are achieved with layered sensor structure. The pressure sensor array, presented in this paper, can be utilized in various robotic systems.

Flexible pressure sensing film based on ultra-sensitive SWCNT/PDMS spheres for monitoring human pulse signals

Journal of Materials Chemistry B ◽

10.1039/c5tb00653h ◽

2015 ◽

Vol 3 (27) ◽

pp. 5436-5441 ◽

Cited By ~ 29

Author(s):

Yan-Long Tai ◽

Zhen-Guo Yang

Keyword(s):

Pressure Sensors ◽

Pressure Sensing ◽

Prosthetic Limbs ◽

Electronic Skin ◽

Essential Components ◽

Biomedical Diagnostics ◽

Healthcare Monitoring ◽

Flexible Pressure Sensors ◽

Human Healthcare

Flexible pressure sensors are essential components of an electronic skin for future attractive applications ranging from human healthcare monitoring to biomedical diagnostics to robotic skins to prosthetic limbs.

Flexible hemispheric microarrays of highly pressure-sensitive sensors based on breath figure method

Nanoscale ◽

10.1039/c8nr01495g ◽

2018 ◽

Vol 10 (22) ◽

pp. 10691-10698 ◽

Cited By ~ 37

Author(s):

Zhihui Wang ◽

Ling Zhang ◽

Jin Liu ◽

Hao Jiang ◽

Chunzhong Li

Keyword(s):

Pressure Sensor ◽

Pressure Sensors ◽

Pressure Sensing ◽

Sensing Range ◽

Pressure Sensitive ◽

Breath Figure ◽

Breath Figure Method ◽

Flexible pressure sensors with interlocked hemispheric microstructures are prepared by a novel breath figure strategy. The subtle microstructure remarkably improves the sensitivity and pressure sensing range of the pressure sensor.