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

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.

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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 ◽

Capacitive Pressure Sensor ◽

Element Analysis ◽

Sequential Coupling ◽

Flexible Pressure Sensors

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.

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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 ◽

Capacitive Pressure Sensor ◽

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.

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A multiscale flexible pressure sensor based on nanovesicle-like hollow microspheres for micro-vibration detection in non-contact mode

Nanoscale ◽

10.1039/c8nr09506j ◽

2019 ◽

Vol 11 (12) ◽

pp. 5737-5745 ◽

Cited By ~ 4

Author(s):

Tie Li ◽

Lili Li ◽

Yuanyuan Bai ◽

Yudong Cao ◽

Qifeng Lu ◽

...

Keyword(s):

Pressure Sensor ◽

Pressure Sensors ◽

Hollow Microspheres ◽

Contact Mode ◽

Vibration Signals ◽

Vibration Detection ◽

Flexible Pressure Sensor ◽

Micro Vibration ◽

Flexible Pressure Sensors

Hierarchical nanovesicle-like hollow microspheres are employed to fabricate flexible pressure sensors for detecting micro-vibration signals in non-contacting mode.

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Self-Restoring Capacitive Pressure Sensor Based on Three-Dimensional Porous Structure and Shape Memory Polymer

Polymers ◽

10.3390/polym13050824 ◽

2021 ◽

Vol 13 (5) ◽

pp. 824

Author(s):

Byunggeon Park ◽

Young Jung ◽

Jong Soo Ko ◽

Jinhyoung Park ◽

Hanchul Cho

Keyword(s):

Porous Structure ◽

Shape Memory ◽

Pressure Sensor ◽

Shape Memory Polymer ◽

Three Dimensional ◽

Pressure Sensors ◽

Capacitive Pressure Sensor ◽

Practical Applications ◽

Flexible Pressure Sensor ◽

Sensing Performance

Highly flexible and compressible porous polyurethane (PU) structures have effectively been applied in capacitive pressure sensors because of the good elastic properties of the PU structures. However, PU porous structure-based pressure sensors have been limited in practical applications owing to their low durability during pressure cycling. Herein, we report a flexible pressure sensor based on a three-dimensional porous structure with notable durability at a compressive pressure of 500 kPa facilitated by the use of a shape memory polymer (SMP). The SMP porous structure was fabricated using a sugar templating process and capillary effect. The use of the SMP resulted in the maintenance of the sensing performance for 100 cycles at 500 kPa; the SMP can restore its original shape within 30 s of heating at 80 °C. The pressure sensor based on the SMP exhibited a higher sensitivity of 0.0223 kPa−1 than a typical PU-based sensor and displayed excellent sensing performance in terms of stability, response time, and hysteresis. Additionally, the proposed sensor was used to detect shoe insole pressures in real time and exhibited remarkable durability and motion differentiation.

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Microdome-Tunable Graphene/Carbon Nanotubes Pressure Sensors Based on Polystyrene Array for Wearable Electronics

Materials ◽

10.3390/ma14237385 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7385

Author(s):

Xingjie Su ◽

Chunli Luo ◽

Weiguo Yan ◽

Junyi Jiao ◽

Dongzhou Zhong

Keyword(s):

Carbon Nanotubes ◽

Pressure Sensor ◽

Self Assembly ◽

Low Cost ◽

Pressure Sensors ◽

Conductive Filler ◽

Human Motion ◽

Wearable Electronics ◽

Flexible Pressure Sensor ◽

Human Finger

Resistive pressure sensors are appealing due to having several advantages, such as simple reading mechanisms, simple construction, and quick dynamic response. Achieving a constantly changeable microstructure of sensing materials is critical for the flexible pressure sensor and remains a difficulty. Herein, a flexible, tunable resistive pressure sensors is developed via simple, low-cost microsphere self-assembly and graphene/carbon nanotubes (CNTs) solution drop coating. The sensor uses polystyrene (PS) microspheres to construct an interlocked dome microstructure with graphene/CNTs as a conductive filler. The results indicate that the interlocked microdome-type pressure sensor has better sensitivity than the single microdome-type and single planar-type without surface microstructure. The pressure sensor’s sensitivity can be adjusted by varying the diameter of PS microspheres. In addition, the resistance of the sensor is also tunable by adjusting the number of graphene/CNT conductive coating layers. The developed flexible pressure sensor effectively detected human finger bending, demonstrating tremendous potential in human motion monitoring.

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Flexible and Transparent Pressure Sensor Based on CNTs Film Microstructure

10.21203/rs.3.rs-1078880/v1 ◽

2021 ◽

Author(s):

Liangliang Liu ◽

Xin Yan

Keyword(s):

Pressure Sensor ◽

Production Cost ◽

Composite Electrode ◽

Pressure Sensors ◽

Wearable Devices ◽

Capacitive Pressure Sensor ◽

Detection Range ◽

Electronic Skin ◽

Film Microstructure ◽

Flexible Pressure Sensors

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.

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Flexible Capacitive Pressure Sensors with Micro-Patterned Porous Dielectric Layer for Wearable Electronics

Journal of Micromechanics and Microengineering ◽

10.1088/1361-6439/ac49a3 ◽

2022 ◽

Author(s):

Jing Wang ◽

Longwei Li ◽

Lanshuang Zhang ◽

Panpan Zhang ◽

Xiong Pu

Keyword(s):

Pressure Sensor ◽

Flexible Electronics ◽

Dielectric Layer ◽

Pressure Sensors ◽

High Sensitivity ◽

Capacitive Sensor ◽

Human Motion ◽

Capacitive Pressure Sensor ◽

Wearable Electronics ◽

Emulsified Water

Abstract Highly sensitive soft sensors play key roles in flexible electronics, which therefore have attracted much attention in recent years. Herein, we report a flexible capacitive pressure sensor with high sensitivity by using engineered micro-patterned porous polydimethylsiloxane (PDMS) dielectric layer through an environmental-friendly fabrication procedure. The porous structure is formed by evaporation of emulsified water droplets during PDMS curing process, while the micro-patterned structure is obtained via molding on sandpaper. Impressively, this structure renders the capacitive sensor with a high sensitivity up to 143.5 MPa-1 at the pressure range of 0.068~150 kPa and excellent anti-fatigue performance over 20,000 cycles. Meanwhile, the sensor can distinguish different motions of the same person or different people doing the same action. Our work illustrates the promising application prospects of this flexible pressure sensor for the security field or human motion monitoring area.

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A Full Printed Flexible Pressure Sensor with Improved Temperature Performance based on Optimized Curing Mechanism

Journal of Imaging Science and Technology ◽

10.2352/j.imagingsci.technol.2022.66.2.020406 ◽

2021 ◽

Author(s):

Jingnan Ma ◽

Mengmeng Liang ◽

Wei Wang

Keyword(s):

High Temperature ◽

Pressure Sensor ◽

Flexible Electronics ◽

Material Selection ◽

Pressure Sensors ◽

Functional Materials ◽

Temperature Performance ◽

Curing Mechanism ◽

Flexible Pressure Sensor ◽

Flexible Pressure Sensors

Printable flexible pressure sensors have many important applications in wearable systems. One major challenge of such a sensor is to maintain sensing properties in high temperature. By optimizing the curing mechanism of the flexible pressure sensor functional materials, this paper proposes a new method of achieving high temperature properties for a full printed sensor. The establishment of curing theory is mainly studied. The printing process of this kind of sensor is systematically stated and tested to check whether it can continue to function at high temperatures. Ultimately a fully-printed flexible pressure sensor with good temperature performance is achieved. The paper focuses around the technical route of “material selection—theoretical analysis —function material preparation—design and preparation of device—device performance evaluation”. Suitable materials are used in flexible pressure sensors and the curing mechanism is established. This proposed technique can be extended to the development of other printable flexible sensors, which can lead to a huge impact on future applications of the flexible electronics.

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A highly sensitive and flexible capacitive pressure sensor based on a micro-arrayed polydimethylsiloxane dielectric layer

Journal of Materials Chemistry C ◽

10.1039/c8tc04297g ◽

2018 ◽

Vol 6 (48) ◽

pp. 13232-13240 ◽

Cited By ~ 38

Author(s):

Longquan Ma ◽

Xingtian Shuai ◽

Yougen Hu ◽

Xianwen Liang ◽

Pengli Zhu ◽

...

Keyword(s):

Pressure Sensor ◽

Dielectric Layer ◽

Sandwich Structure ◽

High Sensitivity ◽

Capacitive Pressure Sensor ◽

Pdms Substrate ◽

Highly Sensitive ◽

Flexible Pressure Sensor

A flexible pressure sensor with high sensitivity has been proposed which consists of a typical sandwich structure by integrating a PDMS substrate with a micro-arrayed PDMS dielectric layer.

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Highly Sensitive, Breathable, and Flexible Pressure Sensor Based on Electrospun Membrane with Assistance of AgNW/TPU as Composite Dielectric Layer

Sensors ◽

10.3390/s20092459 ◽

2020 ◽

Vol 20 (9) ◽

pp. 2459 ◽

Cited By ~ 1

Author(s):

Jie Wang ◽

Yaoyuan Lou ◽

Bin Wang ◽

Qing Sun ◽

Mingwei Zhou ◽

...

Keyword(s):

Pressure Sensor ◽

Dielectric Layer ◽

Silver Nanowires ◽

Synergistic Effects ◽

Pressure Sensors ◽

Mechanical Deformation ◽

Wearable Devices ◽

Electrospun Membrane ◽

Highly Sensitive ◽

Flexible Pressure Sensor

Pressure sensors have been widely used in electronic wearable devices and medical devices to detect tiny physical movements and mechanical deformation. However, it remains a challenge to fabricate desirable, comfortable wearing, and highly sensitive as well as fast responsive sensors to capture human body physiological signs. Here, a new capacitive flexible pressure sensor that is likely to solve this problem was constructed using thermoplastic polyurethane elastomer rubber (TPU) electrospinning nanofiber membranes as a stretchable substrate with the incorporation of silver nanowires (AgNWs) to build a composite dielectric layer. In addition, carbon nanotubes (CNTs) were painted on the TPU membranes as flexible electrodes by screen printing to maintain the flexibility and breathability of the sensors. The flexible pressure sensor could detect tiny body signs; fairly small physical presses and mechanical deformation based on the variation in capacitance due to the synergistic effects of microstructure and easily altered composite permittivity of AgNW/TPU composite dielectric layers. The resultant sensors exhibited high sensitivity (7.24 kPa−1 within the range of 9.0 × 10−3 ~ 0.98 kPa), low detection limit (9.24 Pa), and remarkable breathability as well as fast responsiveness (<55 ms). Moreover, both continuously pressing/releasing cycle over 1000 s and bending over 1000 times did not impair the sensitivity, stability, and durability of this flexible pressure sensor. This proposed strategy combining the elastomer nanofiber membrane and AgNW dopant demonstrates a cost-effective and scalable fabrication of capacitive pressure sensors as a promising application in electronic skins and wearable devices.

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