A magnetic susceptor in a printable filament form is developed for the induction welding of thermoplastic composites. The susceptor is based on Ni particles embedded in a poly-ether-imide matrix. It is extruded and spooled to form a filament which can then be 3D-printed. The susceptor produces heat by hysteresis losses due to the magnetic properties of the Ni particles. As opposed to other typical electrically conductive heating elements, no percolation threshold needs to be achieved to produce heat as the Ni particles individually heat up when exposed to the induction coil’s magnetic field. The heating efficiency of the susceptor filament and its deposition by the fused filament fabrication technique are demonstrated. The susceptor is used to assemble all thermoplastic composite sandwich panels. The sandwich samples are tested by the flatwise tensile test and a tensile strength of 4.6 MPa is obtained, which is equivalent to or higher than reported strengths for typical aerospace-grade sandwich panels. The printable susceptor opens the way to new induction welding or heating applications as it can be printed on a surface to produce a desired heating pattern.

To control solids circulation and optimize design and operating parameters in a circulating fluidized bed full-loop system, measurement and modeling of solids flow behaviors in an aerated standpipe and inclined pipe were conducted. Different aeration gas flows were injected at the inclined pipe, which was equipped with different orifice sizes of 37 mm, 54 mm and 75 mm, for regulating solids flow rates. The magnetic tracer-tracking method, which only needs to inject one small magnetic tracer for each measurement to follow the main solids flow, was successfully demonstrated for measuring sand particles’ real-time discharge rates, with good accuracy and no calibration requirement. A mathematical model was constructed to predict solids discharge rates and investigate the adverse effect of the pressure gradient in the standpipe bed in a full loop fluidized bed system. The optimization of the solids-return and circulation unit could therefore be achieved with the tools developed in this study.

In the present study, the application of a magnetic tracer-tracking method in measuring solids circulation in a fluidized bed standpipe is investigated, due to its advantages of little intervention and cost efficiency, especially in pressurized systems. The method only needs to inject one small magnetic tracer to follow the main solid flow in the standpipe, therefore predicting particles’ real-time velocities. The measurement accuracy was thoroughly tested via comparing to conventional descending and accumulation methods. Main tracer properties, including tracer shape, density, and magnet core, were considered. Solids flow patterns in the standpipe were also regulated by changing orifice sizes and adding an inclined pipe, for the purpose of investigating the measurement accuracy in various conditions. The adverse effect of a narrow orifice on measurement was addressed via constructing a model that includes sand particles’ non-uniform velocity distribution across the standpipe cross-section. To interpret behaviors of tracers varied in size and density, a mathematical model was constructed to describe forces exerted on the tracer in the solids bed. The behaviors of the tracer immersed into the solids bed were also examined, providing an insight to that in a standpipe with continuous solids circulation. The solids bed density was also regulated by varying the mixture of olivine sand and carbonaceous particles at different proportions. The magnetic tracer-tracking method has been successfully validated, demonstrating good measurement accuracy of solids discharge flow rates in the standpipe, particularly avoiding cumbersome calibration. Moreover, the method can also determine sand waving and oscillated discharge behaviors, which might be related to solids’ stick–slip phenomena and is unlikely to be accurately determined using conventional descending and accumulation methods. 

Aim: A reliable tool to visualise children’s early stress signs to prevent dental fear development is needed. The aim was to evaluate the commercially available, CE marked, Shimmer3 GSR + unit’s ability to indicate for stress as a reaction of fear or pain for a non-invasive dental treatment (NI) and an invasive dental treatment (I). Methods: Patients 14–16 years old were invited to undergo an oral check-up (NI) or an orthodontic premolar extraction (I), respectively. Digital data, measured via electrodes and optical pulse probe, placed on the wrist and fingers, monitored by the Shimmer3 GSR + unit, was transferred via Bluetooth to the HP-laptop. The observed digital parameters were: heart rate based on photoplethysmography (PPG), galvanic skin response (GSR), and 3-axis gyroscope and accelerometer signals for hand movements. Protocols for patient self-report scales were used: coloured analogue scale for pain intensity, facial analogue scale for the mood, and a dental fear scale. Descriptive statistics was performed. Results: The NI-group: 20 patients, (14.6 ± 0.5 years), underwent 20 oral check-ups. The I-group: 14 patients, (15.3 ± 0.5 years), underwent 28 premolar extractions. All patients tolerated the Shimmer3 GSR + unit well. The GSR signal increased significantly, at start and during the oral injection, in the I-group. The GSR amplitudes persisted throughout and post the dental injection. No general uniform pattern or high GSR amplitudes were produced regarding NI-group. Conclusions: Considering the limitations of this study, the following conclusions can be made: the invasive treatment resulted in a specific unison GSR pattern, while the non-invasive procedure showed individually scattered GSR reactions. The commercially available CE-marked Shimmer3 GSR + device indicated the patient’s stress response triggered by the invasive anaesthetic procedure. © The Author(s) 2024.

From 2007 in US and from 2022 in EU it is mandatory to use TPMS monitoring in new cars. Sensors mounted in tires require a continuous power supply, which currently only is from batteries. Piezoelectric energy harvesting is a promising technology to harvest energy from tire movement and deformation to prolong usage of batteries and even avoid them inside tires. This study presents a simpler method to simultaneous model the tire deformation and piezoelectric harvester performance by using a new simulation approach - dynamic bending zone. For this, angular and initial velocities were used for rolling motion, while angled polarization was introduced in the model for the piezoelectric material to generate correct voltage from tire deformation. We combined this numerical simulation in COMSOL Multiphysics with real-life measurements of electrical output of a piezoelectric energy harvester that was mounted onto a tire. This modelling approach allowed for 10 times decrease in simulation time as well as simpler investigation of systems parameters influencing the output power. By using experimental data, the simulation could be fine-tuned for material properties and for easier extrapolation of tire deformation with output harvested energy from simulations done at low velocity to the high velocity experimental data.

Screen printed piezoelectric polyvinylidene fluoride?trifluoro ethylene (PVDF?TrFE)-based sensors laminated between glass panes in the temperature range 80?110?°C are presented. No degradation of the piezoelectric signals is observed for the sensors laminated at 110?°C, despite approaching the Curie temperature of the piezoelectric material. The piezoelectric sensors, here monitoring force impact in smart glass applications, are characterized by using a calibrated impact hammer system and standardized impact situations. Stand-alone piezoelectric sensors and piezoelectric sensors integrated on poly(methyl methacrylate) are also evaluated. The piezoelectric constants obtained from the measurements of the nonintegrated piezoelectric sensors are in good agreement with the literature. The piezoelectric sensor response is measured by using either physical electrical contacts between the piezoelectric sensors and the readout electronics, or wirelessly via both noncontact capacitive coupling and Bluetooth low-energy radio link. The developed sensor concept is finally demonstrated in smart window prototypes, in which integrated piezoelectric sensors are used to detect break-in attempts. Additionally, each prototype includes an electrochromic film to control the light transmittance of the window, a screen printed electrochromic display for status indications and wireless communication with an external server, and a holistic approach of hybrid printed electronic systems targeting smart multifunctional glass applications.

We report on the implementation of an induction based, low temperature, high frequency ac susceptometer capable of measuring at frequencies up to 3.5 MHz and at temperatures between 2 K and 300 K. Careful balancing of the detection coils and calibration allow a sample magnetic moment resolution of 5 × 10⁻¹⁰ Am² at 1 MHz. We discuss the design and characterization of the susceptometer and explain the calibration process. We also include some example measurements on the spin ice material CdEr₂S₄ and iron oxide based nanoparticles to illustrate functionality.