This work reports a flexible and wearable nanocomposite made of nitrogen doped carbon dot (N-CD) modified PVDF (PCD) nanocomposite assisted piezoelectric device (PPNCD) that can harvest different ...forms of mechanical energy and convert them into electrical energy. The efficacy of this device is dependent upon its ‘sandwiched’ structure made of PCD nanocomposite wrapped with aluminum electrodes on both sides. Herein, N-doped CD has been incorporated into PVDF matrix for obtaining maximum β-crystalline phase (F(β) ∼ 80.4%), which is confirmed by XRD, FTIR and DSC analysis. The polarizability of the PCD nanocomposite has a great contribution to the total output performance of the device. The polarizability of the film has been measured by using a standard density functional approach. The piezoelectric coefficient (d33) has also been calculated, which is found to be 29 pC/N. Such augmented electrical parameters and enhanced piezoelectric coefficient are further utilized to fabricate the PPNCD device, which is capable to detect human body movements efficiently and can act as a weight sensor with a sensitivity of 10.2 V/kPa (up to 0.5 kPa). Moreover, this device provides a power density of 1979.87μWcm−3 and exhibits an exceptional output performance (VOC ∼ 80V) under periodic finger impartations in comparison to other carbon based piezoelectric nanogenerators. The PPNCD device can illuminate 15 blue/white LEDs and charge a 2.2 μF capacitor within a few seconds under continuous finger impartations. Such a multifunctional device could be a promising candidate for both healthcare monitoring systems and their power supplies.
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Mechanical energy is one of the freely available green energy sources that could be harvested to meet the small-scale energy demand. Piezoelectric nanogenerators can be used to harvest the ...biomechanical energy that is available in everyday human life and power various portable electronics. Herein, a ferroelectric material, i.e., lithium tantalate (LiTaO3), was synthesized and used to fabricate a flexible piezoelectric nanogenerator (FPNG). Generally, ferroelectric materials display a strong electrostatic dipole moment and high piezoelectric coefficient, thus resulting in enhanced electrical performance. First, LiTaO3 nanoparticles were synthesized and loaded into poly(vinylidene difluoride) (PVDF) to form a piezoelectric film and then, the piezoelectric composite film was sandwiched between two aluminum electrodes to fabricate an FPNG. The effect of the electrical performance of FPNG as a function of the concentration of LiTaO3 loaded into PVDF was systematically investigated and optimized. The 2.5 wt % FPNG exhibited open-circuit voltage, short-circuit current, and power density values of ∼18 V, ∼1.2 μA, and ∼25 mW/m2, respectively. Furthermore, the FPNG revealed good electrical stability and mechanical durability. Finally, the FPNG was employed as a weight sensor to harvest various biomechanical energies and operate low-power- electronics.
•A novel weighing sensor is proposed based on the Michelson interferometer.•Optical probes measure the relative displacement of a dual beam structure due to an applied weight.•The energy centrobaric ...correction method is used to enhance resolution and accuracy.•The proposed sensor is highly linear, with low hysteresis, high sensitivity, and high precision.•The proposed sensor is a good candidate for application in complex environments.
A novel weight sensor based on the Michelson interferometer is proposed in this study to meet the demands of complex environments. The sensor uses a dual-beam type elastic element, optimized to enhance its sensitivity. Its deformation under load is sensed by a broadband optical coherence displacement measurement system, which, in combination with the spectrum correction method, enables displacement sensing down to sub-nanometer resolution. An optical interferometric weight sensor with a rated load of 6 kg is fabricated under laboratory conditions, and its performance is verified experimentally. The proposed weight sensor demonstrates good stability and achieves a sensitivity of 146.814 μm/kg, theoretical resolution of 0.004 g, nonlinearity error of 0.034%, maximum repeatability error of 0.036%, and maximum hysteresis error of 0.055%, with the relative error of the identification threshold not exceeding 0.1%. The proposed weighing method and sensor represent a significant improvement over other reported interferometer-type weight sensors.
A flexible weight sensor based on optical fibre macrobending loss, using 1550 nm wavelength light and small fibre bending path lengths is presented. An applied load depresses an impactor layer of ...cylindrical protrusions into a soft mat covered with optical fibre, causing the optical loss of the fibre to increase. An experimental study of two fibre types, two impactor materials, two impactor designs and a range of protrusion bend radii from 3 mm to 10 mm is shown. For weights greater than 2 kg, a linear response in optical loss (dB) is observed for an applied weight load in kg. The proportionality constant between loss and load, and thus the total amount of optical loss for up to 10 kg of weight load, can be tuned by changing the sensor physical parameters, shown here in ranges from 0.5 dB up to 25 dB.
Energy consumption of lift systems is one key issue in modern high-rise buildings, drawing property owners’ attention and accounting for 6% of total electricity consumption by end-use in Hong Kong. A ...Benchmarking Energy Performance Indicator (BEPI), <J/kg-m>, measured in J.kg−1.m−1 and proposed by the first author of this paper for lift installations is mentioned in the Technical Guidelines of the Building Energy Code, as one emerging good engineering practice. BEPI is a fair parameter for comparing energy performance of lifts irrespective of their brand, model, travel, speed, capacity and control. It considers energy performance due to both the motor drive efficiency and traffic control intelligence. However, one main obstacle to make it statutory is the lacking of a generic monitor able to retrieve three sets of real time data (normally unavailable on an existing lift) to compute the BEPI, namely energy consumption, instantaneous car load and traveling distance, and to collect ample data statistically reliable enough to determine an acceptable threshold value. This paper describes the development of a proof-of-concept prototype BEPI monitor by giving full technical details on the rationale and history of development, the hardware components, software framework, and updated numerical results of one implementation inside the headquarters of Electrical & Mechanical Services Department (EMSD) of HKSAR. Experiences in installing and calibrating those external sensors that make the whole system non-disturbing to normal lift operation, as well as the procedures in computing the BEPI, are discussed in greater details. It has been shown that the BEPI is traffic dependent but the weekly average of it is relatively stable, confirming it may be robust enough for benchmarking purpose. The solution described in this paper may help roll out the monitoring of BEPI for all lifts inside and outside Hong Kong.
Stockouts constitute a major challenge in the retail industry. Stockouts are caused by errors related to manual stockkeeping and by the misplacement of items on shelves. Such errors account for up to ...4% of lost sales. Real-time inventory management systems for misplaced items or missing stock detection in retail stores are limited. Accordingly, a conductive polymer-based interactive shelving system for real-time inventory management is developed. The system comprises an 80 × 48 sensor array fabricated by screen-printing a piezoresistive carbon-based conductive polymer layer onto gold interdigitated electrodes deposited on a flexible substrate. Each sensing pixel has dimensions of 5 mm × 5 mm and a sensing area of 4 mm × 4 mm. The sensor mat can detect the shape and weight features of stockkeeping units (SKUs), which can then be analyzed by a TensorFlow model for SKU identification. The developed system is characterized for functional resistance range, uniformity, repeatability, and durability. The accuracy of SKU identification achieved using shape features only and the accuracy of SKU identification achieved using both shape and weight features is 95% and 99.2%, respectively. The key novelty of the work is the development of a deep learning-embedded interactive smart shelving system for retail inventory management by using the shape and weight features of SKU. Also, the developed system helps to detect the SKU if they are stacked one over the other. Furthermore, multiple sensor mats implemented on various shelves in a retail store can be modularized and integrated for monitoring under the control of a single PC. Accordingly, the proposed retail inventory tracking system can facilitate the development of automated “humanless” shops.
This paper describes an automated method and device to conduct the Chair Stand Tests of the Fullerton Functional Test Battery. The Fullerton Functional Test is a suite of physical tests designed to ...assess the physical fitness of older adults. The Chair Stand Tests, which include the Five Times Sit-to-Stand Test (5xSST) and the 30 Second Sit-to-Stand Test (30CST), are the standard for measuring lower-body strength in older adults. However, these tests are performed manually, which can be labor-intensive and prone to error. We developed a sensor-integrated chair that automatically captures the dynamic weight and distribution on the chair. The collected time series weight-sensor data is automatically uploaded for immediate determination of the sit-to-stand timing and counts, as well as providing a record for future comparison of lower-body strength progression. The automatic test administration can provide significant labor savings for medical personnel and deliver much more accurate data. Data from 10 patients showed good agreement between the manually collected and sensor-collected 30CST data (M = 0.5, SD = 1.58, 95% CI = 1.13). Additional data processing will be able to yield measurements of fatigue and balance and evaluate the mechanisms of failed standing attempts.
Dynamic characteristics play a crucial role in evaluating the performance of weight sensors and are essential for achieving fast and accurate weight measurements. This study focuses on a weight ...sensor based on optical coherence displacement. Using finite element analysis, the sensor was numerically simulated. Frequency domain and time domain dynamic response characteristics were explored through harmonic response analysis and transient dynamic analysis. The superior dynamic performance and reduced conditioning time of the non-contact optical coherence-based displacement weight sensor were confirmed via a negative step response experiment that compared the proposed sensing method to strain sensing. Moreover, dynamic performance metrics for the optical coherence displacement-type weight sensor were determined. Ultimately, the sensor’s dynamic performance was enhanced using the pole-zero placement method, decreasing the overshoot to 4.72% and reducing the response time to 0.0132 s. These enhancements broaden the sensor’s operational bandwidth and amplify its dynamic response capabilities.
•Cascaded tapered single fiber interferometer for weight sensing is proposed.•Spectral shift and intensity modulation with increase in weight is calibrated.•Experimental findings validate proposed ...theoretical sensing characteristics.•Technique for sensitivity enhancement of the configuration has been presented.
A practical single-fiber Mach-Zehnder interferometer (SF-MZI) based weight sensor has been proposed and experimentally demonstrated. Considering the two modes interference, a novel mathematical basis corroborating the shift in the output fringe pattern of SF-MZI with applied weight placed on its interference region has been substantiated. Further, a correlation between the average induced birefringence, due to loading of interferometer, and the applied weight has been suggested theoretically and endorsed experimentally for the first time for the suggested scheme. The sensitivity of the proposed configuration was observed to be 112 pm/gm for the applied weights ranges from 0 to 100 gm. For the same weight ranges, the sensitivity of the interferometer, was enhanced, by placing it between phase shifters (PSs) inserted in Sagnac interferometer, to 183 pm/gm and 151 pm/gm, respectively.
