Flexible Ultra-Thin Nanocomposite Based Piezoresistive Pressure Sensors for Foot Pressure Distribution Measurement

Foot pressure measurement plays an essential role in healthcare applications, clinical rehabilitation, sports training and pedestrian navigation. Among various foot pressure measurement techniques, in-shoe sensors are flexible and can measure the pressure distribution accurately. In this paper, we describe the design and characterization of flexible and low-cost multi-walled carbon nanotubes (MWCNT)/Polydimethylsiloxane (PDMS) based pressure sensors for foot pressure monitoring. The sensors have excellent electrical and mechanical properties an show a stable response at constant pressure loadings for over 5000 cycles. They have a high sensitivity of 4.4 kΩ/kPa and the hysteresis effect corresponds to an energy loss of less than 1.7%. The measurement deviation is of maximally 0.13% relative to the maximal relative resistance. The sensors have a measurement range of up to 330 kPa. The experimental investigations show that the sensors have repeatable responses at different pressure loading rates (5 N/s to 50 N/s). In this paper, we focus on the demonstration of the functionality of an in-sole based on MWCNT/PDMS nanocomposite pressure sensors, weighing approx. 9.46 g, by investigating the foot pressure distribution while walking and standing. The foot pressure distribution was investigated by measuring the resistance changes of the pressure sensors for a person while walking and standing. The results show that pressure distribution is higher in the forefoot and the heel while standing in a normal position. The foot pressure distribution is transferred from the heel to the entire foot and further transferred to the forefoot during the first instance of the gait cycle.

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Deep learning approach to estimate foot pressure distribution in walking with application for a cost-effective insole system

Journal of NeuroEngineering and Rehabilitation ◽

10.1186/s12984-022-00987-8 ◽

2022 ◽

Vol 19 (1) ◽

Author(s):

Frederick Mun ◽

Ahnryul Choi

Keyword(s):

Older Adults ◽

Deep Learning ◽

Pressure Distribution ◽

Correlation Coefficient ◽

Short Term Memory ◽

Low Cost ◽

Pressure Sensors ◽

Foot Pressure ◽

Age Related ◽

Pathological Gait

Abstract Background Foot pressure distribution can be used as a quantitative parameter for evaluating anatomical deformity of the foot and for diagnosing and treating pathological gait, falling, and pressure sores in diabetes. The objective of this study was to propose a deep learning model that could predict pressure distribution of the whole foot based on information obtained from a small number of pressure sensors in an insole. Methods Twenty young and twenty older adults walked a straight pathway at a preferred speed with a Pedar-X system in anti-skid socks. A long short-term memory (LSTM) model was used to predict foot pressure distribution. Pressure values of nine major sensors and the remaining 90 sensors in a Pedar-X system were used as input and output for the model, respectively. The performance of the proposed LSTM structure was compared with that of a traditionally used adaptive neuro-fuzzy interference system (ANFIS). A low-cost insole system consisting of a small number of pressure sensors was fabricated. A gait experiment was additionally performed with five young and five older adults, excluding subjects who were used to construct models. The Pedar-X system placed parallelly on top of the insole prototype developed in this study was in anti-skid socks. Sensor values from a low-cost insole prototype were used as input of the LSTM model. The accuracy of the model was evaluated by applying a leave-one-out cross-validation. Results Correlation coefficient and relative root mean square error (RMSE) of the LSTM model were 0.98 (0.92 ~ 0.99) and 7.9 ± 2.3%, respectively, higher than those of the ANFIS model. Additionally, the usefulness of the proposed LSTM model for fabricating a low-cost insole prototype with a small number of sensors was confirmed, showing a correlation coefficient of 0.63 to 0.97 and a relative RMSE of 12.7 ± 7.4%. Conclusions This model can be used as an algorithm to develop a low-cost portable smart insole system to monitor age-related physiological and anatomical alterations in foot. This model has the potential to evaluate clinical rehabilitation status of patients with pathological gait, falling, and various foot pathologies when more data of patients with various diseases are accumulated for training.

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Carbon/Silicone Nanocomposite-Enabled Soft Pressure Sensors with a Liquid-Filled Cell Structure Design for Low Pressure Measurement

Sensors ◽

10.3390/s21144732 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4732

Author(s):

Fei Wang ◽

Xiaoming Tao

Keyword(s):

Pressure Measurement ◽

Cell Structure ◽

Pressure Sensors ◽

High Sensitivity ◽

Humanoid Robots ◽

Low Pressure ◽

Measurement Range ◽

Structure Design ◽

Wearable Electronics ◽

Minimal Resistance

In the fields of humanoid robots, soft robotics, and wearable electronics, the development of artificial skins entails pressure sensors that are low in modulus, high in sensitivity, and minimal in hysteresis. However, few sensors in the literature can meet all the three requirements, especially in the low pressure range (<10 kPa). This article presents a design for such pressure sensors. The bioinspired liquid-filled cell-type structural design endows the sensor with appropriate softness (Young’s modulus < 230 kPa) and high sensitivity (highest at 0.7 kPa−1) to compression forces below 0.65 N (6.8 kPa). The low-end detection limit is ~0.0012 N (13 Pa), only triple the mass of a bee. Minimal resistance hysteresis of the pressure sensor is 7.7%. The low hysteresis is attributed to the study on the carbon/silicone nanocomposite, which reveals the effect of heat treatment on its mechanical and electromechanical hysteresis. Pressure measurement range and sensitivity of the sensor can be tuned by changing the structure and strain gauge parameters. This concept of sensor design, when combined with microfluidics technology, is expected to enable soft, stretchable, and highly precise touch-sensitive artificial skins.

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Development Of PVDF Thick Film Interdigitated Capacitors For Pressure Measurement On Flexible Melinex Substrates

MRS Proceedings ◽

10.1557/proc-870-h2.4 ◽

2005 ◽

Vol 870 ◽

Cited By ~ 1

Author(s):

Arous Arshak ◽

Khalil Arshak ◽

Deirdre Morris ◽

Olga Korostynska ◽

Essa Jafer

Keyword(s):

Polymer Film ◽

Thick Film ◽

Pressure Measurement ◽

Pressure Sensors ◽

High Sensitivity ◽

Strain Gauges ◽

Interdigitated Electrodes ◽

Higher Sensitivity

AbstractIn this work, a PVDF thick film paste was deposited onto interdigitated electrodes to form a capacitor. Two different substrates, alumina and Melinex® were used. Capacitors, fabricated on alumina substrates were tested as strain gauges, and showed a high sensitivity with low hysteresis. Capacitors on Melinex® substrates were tested as pressure sensors by adhering them to planar and cylindrical surfaces and subjecting them to pressures up to 300 kPa. Their sensitivity and hysteresis during cycling were examined and compared. It was found that sensors on cylindrical surfaces showed a higher sensitivity, however the hysteresis was also increased. It is thought that this is due to instabilities in the polymer film, accentuated by stretching of the substrate.

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

Journal of Micromechanics and Microengineering ◽

10.1088/1361-6439/ac388d ◽

2021 ◽

Author(s):

Jiang Zhao ◽

Jiahao Gui ◽

Jinsong Luo ◽

Jing Gao ◽

Caidong Zheng ◽

...

Keyword(s):

Pressure Sensor ◽

Screen Printing ◽

Large Scale ◽

Low Cost ◽

Pressure Sensors ◽

High Sensitivity ◽

Wearable Electronics ◽

Integrated Sensor ◽

Patterned Electrodes ◽

Screen Printed

Abstract 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.

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Flexible and Highly Sensitive Pressure Sensors Based on Microstructured Carbon Nanowalls Electrodes

Nanomaterials ◽

10.3390/nano9040496 ◽

2019 ◽

Vol 9 (4) ◽

pp. 496 ◽

Cited By ~ 10

Author(s):

Xi Zhou ◽

Yongna Zhang ◽

Jun Yang ◽

Jialu Li ◽

Shi Luo ◽

...

Keyword(s):

Pressure Sensor ◽

High Performance ◽

Limit Of Detection ◽

Pressure Sensors ◽

High Sensitivity ◽

Physiological Signals ◽

Healthcare Applications ◽

Highly Sensitive ◽

Carbon Nanowalls ◽

Pressure Regime

Wearable pressure sensors have attracted widespread attention in recent years because of their great potential in human healthcare applications such as physiological signals monitoring. A desirable pressure sensor should possess the advantages of high sensitivity, a simple manufacturing process, and good stability. Here, we present a highly sensitive, simply fabricated wearable resistive pressure sensor based on three-dimensional microstructured carbon nanowalls (CNWs) embedded in a polydimethylsiloxane (PDMS) substrate. The method of using unpolished silicon wafers as templates provides an easy approach to fabricate the irregular microstructure of CNWs/PDMS electrodes, which plays a significant role in increasing the sensitivity and stability of resistive pressure sensors. The sensitivity of the CNWs/PDMS pressure sensor with irregular microstructures is as high as 6.64 kPa−1 in the low-pressure regime, and remains fairly high (0.15 kPa−1) in the high-pressure regime (~10 kPa). Both the relatively short response time of ~30 ms and good reproducibility over 1000 cycles of pressure loading and unloading tests illustrate the high performance of the proposed device. Our pressure sensor exhibits a superior minimal limit of detection of 0.6 Pa, which shows promising potential in detecting human physiological signals such as heart rate. Moreover, it can be turned into an 8 × 8 pixels array to map spatial pressure distribution and realize array sensing imaging.

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High-Sensitivity Flexible Pressure Sensor-Based 3D CNTs Sponge for Human–Computer Interaction

Polymers ◽

10.3390/polym13203465 ◽

2021 ◽

Vol 13 (20) ◽

pp. 3465

Author(s):

Jianli Cui ◽

Xueli Nan ◽

Guirong Shao ◽

Huixia Sun

Keyword(s):

Pressure Sensor ◽

High Performance ◽

Large Scale ◽

Low Cost ◽

Pressure Sensors ◽

Chemical Vapor ◽

High Sensitivity ◽

Wearable Electronics ◽

Wide Range ◽

Flexible Pressure Sensors

Researchers are showing an increasing interest in high-performance flexible pressure sensors owing to their potential uses in wearable electronics, bionic skin, and human–machine interactions, etc. However, the vast majority of these flexible pressure sensors require extensive nano-architectural design, which both complicates their manufacturing and is time-consuming. Thus, a low-cost technology which can be applied on a large scale is highly desirable for the manufacture of flexible pressure-sensitive materials that have a high sensitivity over a wide range of pressures. This work is based on the use of a three-dimensional elastic porous carbon nanotubes (CNTs) sponge as the conductive layer to fabricate a novel flexible piezoresistive sensor. The synthesis of a CNTs sponge was achieved by chemical vapor deposition, the basic underlying principle governing the sensing behavior of the CNTs sponge-based pressure sensor and was illustrated by employing in situ scanning electron microscopy. The CNTs sponge-based sensor has a quick response time of ~105 ms, a high sensitivity extending across a broad pressure range (less than 10 kPa for 809 kPa−1) and possesses an outstanding permanence over 4,000 cycles. Furthermore, a 16-pixel wireless sensor system was designed and a series of applications have been demonstrated. Its potential applications in the visualizing pressure distribution and an example of human–machine communication were also demonstrated.

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Temperature measurement performance of silicon piezoresistive MEMS pressure sensors for industrial applications

Facta universitatis - series Electronics and Energetics ◽

10.2298/fuee1501123f ◽

2015 ◽

Vol 28 (1) ◽

pp. 123-131 ◽

Cited By ~ 5

Author(s):

Milos Frantlovic ◽

Ivana Jokic ◽

Zarko Lazic ◽

Branko Vukelic ◽

Marko Obradov ◽

...

Keyword(s):

Temperature Measurement ◽

Low Cost ◽

Pressure Sensors ◽

High Sensitivity ◽

Correction Method ◽

Industrial Applications ◽

Sensor Applications ◽

Piezoresistive Pressure Sensors ◽

Mems Pressure Sensors

Temperature and pressure are the most common parameters to be measured and monitored not only in industrial processes but in many other fields from vehicles and healthcare to household appliances. Silicon microelectromechanical (MEMS) piezoresistive pressure sensors are the first and the most successful MEMS sensors, offering high sensitivity, solid-state reliability and small dimensions at a low cost achieved by mass production. The inherent temperature dependence of the output signal of such sensors adversely affects their pressure measurement performance, necessitating the use of correction methods in a majority of cases. However, the same effect can be utilized for temperature measurement, thus enabling new sensor applications. In this paper we perform characterization of MEMS piezoresistive pressure sensors for temperature measurement, propose a sensor correction method, and demonstrate that the measurement error as low as ? 0.3?C can be achieved.

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Novel Pressure Sensors Made from Nanocomposites (Biodegradable Polymers–Metal Oxide Nanoparticles): Fabrication and Characterization

Ukrainian Journal of Physics ◽

10.15407/ujpe63.8.754 ◽

2018 ◽

Vol 63 (8) ◽

pp. 754 ◽

Cited By ~ 8

Author(s):

A. Hashim ◽

A. Hadi

Keyword(s):

Electrical Conductivity ◽

Dielectric Properties ◽

Low Cost ◽

Metal Oxide Nanoparticles ◽

Pressure Sensors ◽

High Sensitivity ◽

Oxide Nanoparticles ◽

Ac Electrical Conductivity ◽

Dc Electrical Conductivity ◽

Pressure Sensitive

This paper aims to the preparation of novel pressure-sensitive nanocomposites with low cost, light weight, and good sensitivity. The nanocomposites of polyvinyl alcohol, polyacrylic acid, and lead oxide nanoparticles have been investigated. The dielectric properties and dc electrical conductivity of (PVA–PAA–PbO2) nanocomposites have been studied. The dielectric properties of nanocomposites were measured in the frequency range (100 Hz–5 MHz). The experimental results showed that the dielectric constant and dielectric loss of (PVA–PAA–PbO2) nanocomposites decrease, as the frequency increases, and they increase with the concentrations of PbO2 nanoparticles. The ac electrical conductivity of (PVA–PAA–PbO2) nanocomposites increases with the frequency and the concentrations of PbO2 nanoparticles. The dc electrical conductivity of (PVA–PAA–PbO2) nanocomposites also increases with the concentrations of PbO2 nanoparticles. The application of pressure-sensitive nanocomposites has been examined in the pressure interval (60–200) bar. The results showed that the electrical resistance of (PVA–PAA–PbO2) pressure-sensitive nanocomposites decreases, as the compressive stress increases. The (PVA–PAA–PbO2) nanocomposites have high sensitivity to pressure.

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Static and Total Pressure Sensor Development Methodology based on Elastic Sensing Elements and Optical Rules

Herald of the Bauman Moscow State Technical University Series Instrument Engineering ◽

10.18698/0236-3933-2021-1-33-50 ◽

2021 ◽

pp. 33-50

Author(s):

R.A. Borisov ◽

I.V. Antonets ◽

A.V. Krotov

Keyword(s):

Pressure Sensor ◽

Total Pressure ◽

Air Flow ◽

Experimental Studies ◽

Pressure Sensors ◽

High Sensitivity ◽

Measurement Range ◽

Design Parameters ◽

Signal System ◽

Digital Information

Information on the parameters of static atmospheric pressure and total pressure of the incoming air flow is the primary information in the air signal system, which is part of the integrated aircraft control system. This information makes it possible to calculate the altitude and speed of the aircraft for automated and automatic control. Static and total pressures are measured by aerometric parameter sensors, whose technical characteristics largely determine the range and values of the measurement accuracy of the air signal system. Relying on the requirements for aircraft flight safety and in accordance with the existing standards for horizontal and vertical separation, rather stringent requirements are imposed on the accuracy of air pressure measurement. Instrumental errors in measuring static and total air flow pressures with a probability of 0.95 should not exceed 0.02 and 0.05 % of the measurement range. The considered original aerometric pressure sensor based on an optical rule, whose high sensitivity requires minimal deformation of the elastic sensitive element, makes it possible to fulfill these requirements. The non-contact digital information retrieval and the operation of the information system under vacuum conditions significantly increased the efficiency of measurement processes. The paper focuses on an algorithm for calculating the main design parameters of elastic sensitive elements in almost the entire range of their standard sizes taking into account the technical capabilities of the secondary converter. The results of the experiments and experimental studies confirmed the sufficiency of theoretical methods for calculating the parameters of elastic elements for pressure sensors

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