Pressure Mapping Research Articles

EFFECT OF SPINAL FUSION ON BIOMECHANICS OF FACET JOINTS: SYNCHRONIZED SPATIO-TEMPORAL AND MECHANICAL ANALYSIS

ObjectivesUnderstanding lumbar facet joint involvement and biomechanical changes post spinal fusion is limited. This study aimed to establish an in vitro model assessing mechanical effects of fusion on human lumbar facet joints, employing synchronized motion, pressure, and stiffness analysis.Methods and ResultsSeven human lumbar spinal units (age 54 to 92, ethics 15/YH/0096) underwent fusion via a partial nucleotomy model mimicking a lateral cage approach with PMMA cement injection. Mechanical testing pre and post-fusion included measuring compressive displacement and load, local motion capture, and pressure mapping at the facet joints. pQCT imaging (82 microns isotropic) was carried out at each stage to assess the integrity of the vertebral endplates and quantify the amount of cement injected.Before fusion, relative facet joint displacement (6.5 ± 4.1 mm) at maximum load (1.1 kN) exceeded crosshead displacement (3.9 ± 1.5 mm), with loads transferred across both facet joints. After fusion, facet displacement (2.0 ± 1.2 mm) reduced compared to pre-fusion, as was the crosshead displacement (2.2 ± 0.6 mm). Post-fusion loads (71.4 ± 73.2 N) transferred were reduced compared to pre-fusion levels (194.5 ± 125.4 N). Analysis of CT images showed no endplate damage post-fusion, whilst the IVD tissue: cement volume ratio did not correlate with the post-fusion behaviour of the specimens.ConclusionAn in vitro model showed significant facet movement reduction with stand-alone interbody cage placement. This technique identifies changes in facet movement post-fusion, potentially contributing to subsequent spinal degeneration, highlighting its utility in biomechanical assessment.Conflicts of interestNoneSources of fundingThis work was funded by EPSRC, under grant EP/W015617/1.

Numerical Analysis of the Dynamic Properties of Bionic Raster Ceilings.

In this study, a numerical dynamic analysis of ceiling raster panels was performed. The analysis was conducted on panels designed with inspiration from bionics. The purpose of the analysis was to enable optimisation of the location of the holes in the designed slabs in order to achieve the preferred dynamic properties, including the natural frequencies of the slabs and an appropriate airflow to avoid the occurrence of resonance. Three different types of panels were used and a total of fifteen panels were designed in terms of their geometry, with circular, elliptical, and hexagonal perforations, made of different materials: polypropylene PP, wood, and aluminium. Then, using the finite element method and ANSYS 2023 R1 software, the airflow over the ceiling panels and their natural frequencies and vibration modes were analysed. The analysis took into account not only the shape of the openings, but also their percentage area relative to the total panel area and different airflow velocities. In addition, the results were compared in an analytical way with those obtained for a solid slab. The results obtained include findings on the mode shapes and values of the vibration frequencies of the plates, air pressure maps, histograms, and plots of the pressure dependence on the surface area of the plate openings.

The Relationship Between Sleep Quality and Mean Arterial Pressure (Map) Value In The Elderly With Hypertension In The Working Area Of The Palasari Health Center, Subang Regency

Abraham Maslow (1984) proposed a hierarchy of needs that includes 5 basic needs and desires in humans. The 5 levels of basic human needs are physiological needs Basic human needs are the elements needed to maintain balance, both physiologically and psychologically. One of them is sleep where humans need to meet their basic needs to achieve optimal energy needs. The current investigation employs a cross-sectional research design, utilizing a correlational approach to examine the research question at hand. The sampling method in this research used simple random sampling, the total sample was 94 respondents. The research instrument used the PSQI questionnaire and digital sphygmomanometer instrument. Where the Spearman Rank test results were obtained with a p-value < 0,001 and a Correlation Coefficient value of 0.503. So, based on the results of this research, it can be concluded that there is a relationship between sleep quality and MAP value in elderly people with hypertension in the work area of ​​the Palasari Health Center, Subang Regency in 2024 with a p-value<0,001 with a positive correlation coefficient. It is expected that the research will serve as a benchmark for future researchers in the field of education, particularly in their endeavors to enhance the quality of sleep in elderly individuals afflicted with hypertension, utilizing the MAP standards.

Battery-Free, Wireless Multi-Modal Sensor, and Actuator Array System for Pressure Injury Prevention.

Simultaneous monitoring of critical parameters (e.g., pressure, shear, and temperature) at bony prominences is essential for the prevention of pressure injuries in a systematic manner. However, the development of wireless sensor array for accurate mapping of risk factors has been limited due to the challenges in the convergence of wireless technologies and wearable sensor arrays with a thin and small form factor. Herein, a battery-free, wireless, miniaturized multi-modal sensor array is introduced for continuous mapping of pressure, shear, and temperature at skin interfaces. The sensor array includes an integrated pressure and shear sensor consisting of 3D strain gauges and micromachined components. The mechanically decoupled design of the integrated sensor enables reliable data acquisition of pressure and shear at skin interfaces without the need for additional data processing. The sensor platform enables the analysis of interplay among localized pressure, shear, and temperature in response to changes in the patient's movement, posture, and bed inclination. The validation trials using a novel combination of wireless sensor arrays and customized pneumatic actuator demonstrate the efficacy of the platform in continuous monitoring and efficient redistribution of pressure and shear without repositioning, thereby improving the patient's quality of life.

Mapping global land conversion pressure to support conservation planning

Proactively identifying where land conversion might occur is critical to targeted and effective conservation planning. Previous efforts to map future habitat loss have largely focused on forested systems and have been limited in their consideration of drivers of loss. We developed a 1-km resolution, global map of land conversion pressure from multiple drivers, referred to as the conversion pressure index (CPI). The CPI combines past rates of anthropogenic change, as measured by temporal human modification maps, with suitability maps for potential future expansion by large-scale development. The CPI thus offers a new way to measure a cumulative gradient of anthropogenic pressure as opposed to categorical land cover change. We find that nearly 23% of land across 200 countries have relatively high conversion pressure, potentially impacting over 460 million ha of intact natural lands. We illustrate how this information can be used to identify areas for proactive conservation to avoid future loss and ensure that national commitments under the Kunming-Montreal Global Biodiversity and Paris Agreement Climate Frameworks are upheld.

Geometry-modulated all organic 3D printed smart PLA fibers for flextension amplified giant mechanical energy harvesting and Machine learning assisted pressure mapping

Piezoelectret sensors offer a promising avenue for harvesting abundant mechanical energy in the environment, providing a sustainable power solution for low-powered electronics. However, effectively harnessing large impact mechanical energy remains a challenge. In this study, we introduce a novel 3D cylindrical self-powered piezoelectret sensor capable of converting irregular axial impact forces into uniform radial pressures, enabling efficient large-scale impact mechanical energy harvesting. The cylindrical piezoelectret sensor, operating via a flextensional mechanism, was fabricated using 3D printed poly(lactic acid) (PLA) fibers as the piezoelectret layer and poly(3,4-ethylenedioxythiophene) (PEDOT)-coated PLA as the electrode layer. Our cylindrical sensor demonstrates the output voltage, and current of ∼ 11.4 V and 7.2 μA, representing remarkable improvement of 250 % and 160 % respectively, compared to flat fiber membrane device. Furthermore, we leverage IoT connectivity and machine learning techniques to utilize the fabricated robotic sensor for pressure mapping applications. Through machine learning algorithms, we achieve a remarkable accuracy of 100 % in character identification based on sensor data. This work highlights the potential of organic robotic sensors for efficient energy harvesting and intelligent pressure mapping applications, paving the way for the development of sustainable and adaptive sensor systems for various real-world scenarios.

Junction Piezotronic Transistor Arrays Based on Patterned ZnO Nanowires for High-Resolution Tactile and Photo Mapping.

Recently, a great deal of interest has been focused on developing sensors that can measure both pressure and light. However, traditional sensors are difficult to integrate into silicon (Si)-based integrated circuits. Therefore, it is particularly important to design a sensor that operates on a new principle. In this paper, junction piezotronic transistor (JPT) arrays based on zinc oxide (ZnO) nanowire are demonstrated. And the JPT arrays show high spatial resolution pressure and light mapping with 195 dpi. Because ZnO nanowires are arranged vertically above the p-type Si channel's center of the transistor, the width of the heterojunction depletion region is constricted by the positive piezoelectric potential generated by strained ZnO. In addition, photogenerated charge carriers can be created in the Si channel when JPT is stimulated by light, which increases its electrical conductivity. Consequently, the external pressure and light distribution information can be obtained from the variation in the output current of the device. The prepared JPT arrays can be compatible with Si transistors, which make them highly competitive and make it possible to incorporate both pressure and light sensors into large integrated circuits. This work will contribute to many applications, such as intelligent clothing, human-computer interaction, and electronic skin.

Understanding the Biomechanics of Musculoskeletal Injuries in High-Risk Environmental Conditions

The present study examines the biomechanics of musculoskeletal injuries in high-risk environmental conditions by thoroughly analyzing diverse data sources and employing various methodologies. This study utilizes motion analysis, force sensor measurements, computer simulations, and biomechanical testing to examine the various factors contributing to musculoskeletal injuries. The analysis of motion indicates that specific tests, namely varus test, impose considerably greater biomechanical stress, thereby emphasizing their susceptibility to causing injuries. The force sensor data reveals that pressure mapping system is responsible for exerting the highest force, raising concerns regarding its potential impact on the risk of injury. According to computer simulations, various injury risks are associated with different conditions, with load carriage exhibiting the highest risk. The analysis of joint stability during biomechanical testing reveals discrepancies in joint stability levels across different tasks. Outliers within the dataset highlight tasks that exhibit notable concerns regarding joint stability. Moreover, supplementary motion analysis data about various task variants, such as Sulcus sign and vasus stress test unveils distinct variations that lead to heightened levels of biomechanical stress. The discoveries mentioned above offer valuable perspectives on the biomechanical foundations of musculoskeletal injuries in environments with elevated risk levels. The aforementioned findings emphasize the necessity of implementing focused interventions, enhancing equipment design, and implementing heightened safety measures to reduce the risks of injury effectively. The present study establishes a fundamental basis for subsequent research endeavors and proposes approaches designed to safeguard the welfare of individuals operating in demanding contexts.

Patient-specific deep learning for 3D protoacoustic image reconstruction and dose verification in proton therapy.

Protoacoustic (PA) imaging has the potential to provide real-time 3D dose verification of proton therapy. However, PA images are susceptible to severe distortion due to limited angle acquisition. Our previous studies showed the potential of using deep learning to enhance PA images. As the model was trained using a limited number of patients' data, its efficacy was limited when applied to individualpatients. In this study, we developed a patient-specific deep learning method for protoacoustic imaging to improve the reconstruction quality of protoacoustic imaging and the accuracy of dose verification for individualpatients. Our method consists of two stages: in the first stage, a group model is trained from a diverse training set containing all patients, where a novel deep learning network is employed to directly reconstruct the initial pressure maps from the radiofrequency (RF) signals; in the second stage, we apply transfer learning on the pre-trained group model using patient-specific dataset derived from a novel data augmentation method to tune it into a patient-specific model. Raw PA signals were simulated based on computed tomography (CT) images and the pressure map derived from the planned dose. The reconstructed PA images were evaluated against the ground truth by using the root mean squared errors (RMSE), structural similarity index measure (SSIM) and gamma index on 10 specific prostate cancer patients. The significance level was evaluated by t-test with the p-value threshold of 0.05 compared with the results from the groupmodel. The patient-specific model achieved an average RMSE of 0.014 ( ), and an average SSIM of 0.981 ( ), out-performing the group model. Qualitative results also demonstrated that our patient-specific approach acquired better imaging quality with more details reconstructed when comparing with the group model. Dose verification achieved an average RMSE of 0.011 ( ), and an average SSIM of 0.995 ( ). Gamma index evaluation demonstrated a high agreement (97.4% [ ] and 97.9% [ ] for 1%/3 and 1%/5mm) between the predicted and the ground truth dose maps. Our approach approximately took 6 s to reconstruct PA images for each patient, demonstrating its feasibility for online 3D dose verification for prostate protontherapy. Our method demonstrated the feasibility of achieving 3D high-precision PA-based dose verification using patient-specific deep-learning approaches, which can potentially be used to guide the treatment to mitigate the impact of range uncertainty and improve the precision. Further studies are needed to validate the clinical impact of thetechnique.

Towards chemical source tracking and characterization using physics-informed neural networks

This paper presents a new algorithm using physics-informed neural networks (PINNs) to track and characterize spatio-temporally varying chemical sources based on time-resolved measurements of chemical concentration, fluid velocity, and pressure. Chemical source emission functions, chemical concentration, fluid velocity and fluid pressure fields are modeled as multi-layer perceptrons (MLPs). During the training process, sensors readings of chemical concentration, fluid velocity, and fluid pressure are matched to the output of the respective MLPs at the given spatio-temporal locations. Simultaneously, the physics of fluid flow and chemical dispersion at an arbitrary number of spatio-temporal locations in the domain of interest are enforced through regularization. Once trained, the constituent MLPs can be evaluated to generate the time resolved maps of source emissions, chemical concentration, fluid velocity and pressure. Extensive numerical simulation validate the method, including scenarios with both static and dynamic sources in complex flow fields. This innovative approach marks a significant advancement in environmental monitoring technologies.

Correlation analysis of central venous pressure and Intra-thoracic pressures in Acute Respiratory Distress Syndrome mechanical ventilated patients, a pilot Study

Abstract Background Positive end expiratory pressure can affect measurement of central venous pressure through increased intrathoracic pressure. However, when positive end expiratory pressure (PEEP) is applied, central venous pressure and pleural pressure often increases more than right atrial pressure, so that transmural right atrial pressure (true filling pressure) decreases. Aim of the study Primary end point was to recognizing correlation coefficient between mean CVP and intra- thoracic pressures on volume-controlled mode and spontaneous modes on same population of mechanically ventilated ARDS patients. The secondary end point is to compare the correlation coefficient R during both modes with parameters of ventilatory settings. Patient and Methods A cohort observational prospective study was done enrolling single group of patients with acute respiratory distress syndrome, who necessitate mechanical ventilation more than two days after connection to ventilators, the study was performed with demonstration of central venous pressure in cmH2O upon application of needed PEEP. Central venous catheter inserted for measuring CVP were processed in accordance with the standard guidelines. Results There were statistically significant differences between control and support group regarding the PEEP, Plateau pressure, mean CVP and mean airway pressure MAP. The data were higher in control than support group with p-value <0.001, 0.002 and 0.004, respectively. There was statistically significant positive correlation between R and CVP in the control group with p < 0.001 and r = 0.918. There was statistically significant positive correlation between R and ΔPIT in support group with p 0.001 and r = 0.926. The correlation between CVP and R among the control group was R = 0.028 + 0.032 * CVP with p-value <0.001, whereas the correlation between ΔPIT and R among the support group was R = 0.465 + 0.020 * ΔPIT with p-value = 0.022 Conclusion The relation between hemodynamics change of central venous pressures and intrathoracic pressure is new independent marker for evaluating ARDS mechanically ventilated patients. Values of R correlation are different in controlled mode relative to spontaneous mode during ARDS ventilated patients.

Stability of ischial pressure with 3D thermoplastic elastomer cushion and the characteristics of four types of cushions in pressure redistribution.

Wheelchair cushions are recommended to be used with wheelchair and can protect the buttocks from pain and injury by relieving interface pressure for wheelchair users. However, further investigations are required for proper use in response to the development of new types of wheelchair cushions. The objective of this study was to evaluate physical characteristics of wheelchair cushions by comparing pressure redistributing effects of four types of cushions. The participants were 16 healthy adults who consented to participate in this study. A pressure mapping system (CONFORMat, Nitta Corp.) was used for the measurements. Pressure at ischium was measured immediately after the stabilization of the sitting posture and 10 minutes after. The pressure at ischium significantly decreased with any wheelchair cushions (P < 0.01). A significant negative correlation between body mass index and pressure at ischium was observed without a wheelchair cushion (r = - 0.70), however, the correlation disappeared upon use of a wheelchair cushion. The pressure at ischium increased over time with cushions of urethane, air, and urethane-air hybrid while that with the 3D thermoplastic elastomer cushion did not, and the change in the pressure was statistically less than that in other cushions (P < 0.01). Use of wheelchair cushions was effective in redistribution of the pressure at ischium, and the overtime change in the pressure depends on the type of used cushions.

Pressure Interpolation in Water Distribution Networks by Using Gaussian Processes: Application to Leak Diagnosis

This work presents the reconstruction of the pressure head map of a water distribution system (WDS). This approach relies on historical data collected from a reduced number of sensors placed at some nodes of the WDS. Thus, a Gaussian regression process is then applied to estimate the pressure head at those nodes without a sensor, which allows the reconstruction of the pressure map for the whole network. Then, for leak diagnosis purposes, a dataset of pressure head maps of the WDN is created considering leaky scenarios, and a correlation method is applied to estimate the leak location. Then, for clarity, the Hanoi network is used to evaluate the performance of this leak diagnosis strategy in a simulation environment, assuming the availability of only three sensors. The results showed the potential for pressure head map reconstruction and leak localization.

Consolidation and seepage solutions in enclosure space based on non-zero-constant values boundary.

Research is ongoing to find solutions to the problem of Consolidation and seepage in saturated clay in enclosure space. Firstly, the boundary of non-zero-constant values is established, considering the seepage boundary of the clay is affected by pumping water or lowering boundary pressure on the site. Secondly, the differential equation is established to reflect the spatial and temporal variations of excess pore water pressure dissipation in the clay in enclosure space, and the solution is derived using variable separation methods. Finally, based on results of the solution derived, contour maps of the water pressure are drawn corresponding with the different inhomogeneous boundary conditions.

A Visual-Inertial Pressure Fusion-Based Underwater Simultaneous Localization and Mapping System.

Detecting objects, particularly naval mines, on the seafloor is a complex task. In naval mine countermeasures (MCM) operations, sidescan or synthetic aperture sonars have been used to search large areas. However, a single sensor cannot meet the requirements of high-precision autonomous navigation. Based on the ORB-SLAM3-VI framework, we propose ORB-SLAM3-VIP, which integrates a depth sensor, an IMU sensor and an optical sensor. This method integrates the measurements of depth sensors and an IMU sensor into the visual SLAM algorithm through tight coupling, and establishes a multi-sensor fusion SLAM model. Depth constraints are introduced into the process of initialization, scale fine-tuning, tracking and mapping to constrain the position of the sensor in the z-axis and improve the accuracy of pose estimation and map scale estimate. The test on seven sets of underwater multi-sensor sequence data in the AQUALOC dataset shows that, compared with ORB-SLAM3-VI, the ORB-SLAM3-VIP system proposed in this paper reduces the scale error in all sequences by up to 41.2%, and reduces the trajectory error by up to 41.2%. The square root has also been reduced by up to 41.6%.

Effect of attachment flash on clear aligner force delivery: an in vitro study

BackgroundThe introduction of auxiliaries such as composite attachment has improved the force delivery of clear aligner (CA) therapy. However, the placement of the attachment may give rise to a flash, defined as excess resin around the attachment which may affect CA force delivery. This in vitro study aims to determine the differences in the force generated by the attachment in the presence or absence of flash in CA.Materials and methodsTristar Trubalance aligner sheets were used to fabricate the CAs. Thirty-four resin models were 3D printed and 17 each, were bonded with ellipsoidal or rectangular attachments on maxillary right central incisors. Fuji Prescale pressure film was used to measure the force generated by the attachment of CA. The images of colour density produced on the films were processed using a calibrated pressure mapping system utilising image processing techniques and topographical force mapping to quantify the force. The force measurement process was repeated after the flash was removed from the attachment using tungsten-carbide bur on a slow-speed handpiece.ResultsThe intraclass correlation coefficient showed excellent reliability (ICC = 0.96, 95% CI = 0.92–0.98). The average mean force exerted by ellipsoidal attachments with flash was 8.05 ± 0.16 N, while 8.11 ± 0.18 N was without flash. As for rectangular attachments, the average mean force with flash was 8.48 ± 0.27 N, while 8.53 ± 0.13 N was without flash. Paired t-test revealed no statistically significant difference in the mean force exerted by CA in the presence or absence of flash for both ellipsoidal (p = 0.07) and rectangular attachments (p = 0.41). Rectangular attachments generated statistically significantly (p < 0.001) higher mean force than ellipsoidal attachments for flash and without flash.ConclusionAlthough rectangular attachment generated a significantly higher force than ellipsoidal attachment, the force generated by both attachments in the presence or absence of flash is similar (p > 0.05).

Smart seat cushion feasibility pilot study: automated interface pressure modulation of individuals with spinal cord Injury

This study investigates the functionality and feasibility of a novel smart seat cushion system designed for wheelchair users with spinal cord injuries. The cushion, equipped with air cells that serve as both sensors and actuators, was tested on 24 participants for its real-time pressure mapping, automated pressure redistribution, and pressure offloading functions. A commercial pressure mat was concurrently used to validate the cushion’s pressure modulation functions. Additionally, the perceived comfort of the cushion was evaluated using General Discomfort Assessment (GDA) and Discomfort Intensity (DIS) scores, which provided insights into participants’ overall comfort and discomfort levels. Real-time pressure profiles generated by the cushion resembled commercial pressure mat readings. During tests with individuals with spinal cord injury, the cushion was able to dynamically generate and display the real-time pressure profile of a seated individual with strong precision (correlation to commercial pressure mat: r ranging from 0.76 to 0.88), providing effective input into pressure modulation functions. Pressure redistribution algorithms eliminated peak pressure and reduced the overall pressure at the interface. Pressure offloading algorithms automatically identified the regions with the highest interface pressure and subsequently relieved the pressure from those areas. User feedback showed that the cushion was comfortable after redistribution and offloading. This work demonstrated the feasibility of an advanced smart seat cushion system for wheelchair users with spinal cord injuries. The cushion was capable of redistributing pressure evenly across the seating surface, ensuring user’s comfort. Additionally, it identifies and eliminates high-pressure points, further improving comfort and reducing the risk of pressure injuries.

Endothelial function cannot be assessed by the reactive hyperemia following occlusion

Reactive hyperemia (RH) and the post occlusive reactive hyperemia (PORH) are known to assess vascular function in vivo and referred as useful prognostic tools in vascular medicine. However, its translation to clinical practice is poor due to important unsolved inconsistencies. Our group has been studying the adaptive responses following RH. Here we clarify the involved mechanism, its impact on general hemodynamics and the significance of these responses. A convenience sample of fourteen healthy women (48.0 ± 8.0 y.o.) was selected, all being normotensive non-menopausal, with no signs of vascular impairment (normal ankle-brachial index and mean arterial pressure MAP), and with (self-reported) equivalent levels of physical activity. The study followed all principles of good clinical practice established for human research and was previously approved by the institutional Ethics Committee. The protocol included three phases—a baseline register (Phase I) during rest, giving place to the occlusion as part of the PORH maneuver challenge period (Phase II) with one minute, followed by a ten-minute recovery period (Phase III). PORH was performed on one randomly chosen upper limb, using the cuff of the TASK FORCE® platform for the continuous monitoring of blood pressure and hemodynamics. After baseline acquisition, the cuff was rapidly inflated with 200 mmHg to occlude the brachial artery for one minute. Then the cuff was rapidly deflated, and signals registered for recovery recordings. Perfusion was measured in both hands by laser Doppler flowmetry (3rd finger) with a Perimed5000 system. To confirm previous evidence regarding the mechanism(s) involved, we also accessed the RH impact(s) on the contralateral forearm skin circulation by functional imaging using a multi-scan photoptoacoustic tomography (PAT) (MSOT iThera system). The tissue hypoxia related to RH-PORH is referred to evoke a local vasodilation, such that hyperemia occurs following the cessation of occlusion. Thus, any reduction of this response has been associated to endothelial impairment. However, our studies have shown suffcient evidence of a centrally mediated reflex rather than a local response mediated by local vasodilators. In fact, LDF clearly detected significant perfusion reductions in both hands during and following occlusion, more pronounced in the challenged limb, while PAT confirmed similar changes in the superficial plexus on the contralateral forearm. Additionally of interest, no significant hemodynamical changes were found with PORH apart from MAP when comparing recovery with baseline periods. Our results clearly show that the physiological significance of RH or POHR reduction can no longer be regarded to solely represent “endothelial disfunction” but rather an expression of a global adaptive hemodynamical response, centrally mediated, that might originate essential endpoints also measurable in the contralateral limb, with clinical utility. This research was financed by national funds through FCT - Foundation for Science and Technology, I.P. (Portugal), under the [UIDB/04567/2020] and [UIDP/ 04567/2020] projects, and by COFAC/ALIES for the use of the photoacoustic instrument. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Measurement of the local static mechanical pressure of earplugs

Earplugs are used in various critical industrial sectors, such as construction, aviation, military and defense, transportation, and healthcare. However, they present inherent drawbacks, notably discomfort that can lead to inconsistent and incorrect use, thereby leaving a significant proportion of workers vulnerable to irreversible hearing damage, ranging from tinnitus to deafness. This discomfort is closely linked to a physical parameter known as static mechanical pressure (SMP), representing the pressure exerted by earplugs on the earcanal walls. Determining the SMP is crucial for developing earplugs that prioritize comfort. However, experimental studies in this area are scarce and there is no experimental set-up capable of measuring the SMP whether in vivo or ex vivo. The objective of this paper is to fill this gap by presenting a novel experimental system designed to mimic a real earcanal, equipped with an optical probe for precise pressure measurements at various points along the earcanal. This precision-targeted methodology holds the promise of yielding a comprehensive pressure map spanning the entirety of the contact area between the earplug and earcanal, thereby offering unprecedented insights into SMP distribution. To validate our test bench, we conducted experiments using cylindrical rolled-down PVC earplugs inserted into a rigid cylindrical earcanal replica of varying radii. We compared our results with data obtained from a commercially available radial force tester commonly used in investigating stent grafts. Once validation was achieved, we expanded our investigation to measure SMP across various types of earplugs. Additionally, we designed and measured the SMP using roll-down foam earplugs in an artificial earcanal shaped to resemble the human anatomy. Our experimental findings were corroborated with data from finite element method (FEM) numerical calculations. Apart from providing the first comprehensive characterization of the static mechanical pressure exerted by earplugs, our research reveals that with roll-down foam earplugs, increased compression prior to insertion leads to reduced SMP. The versatility of our specially designed test bench allows for mapping SMP caused by earplugs across diverse earcanal shapes. Integration of this instrument into design frameworks holds promise for enhancing the physical comfort of earplugs and, consequently, improving their overall efficacy in hearing protection.

An electrical impedance tomography based artificial soft skin pressure sensor: Characterisation and force modelling

Using electrical impedance tomography (EIT) to drive a pressure mapping device shows great potential, due to the customisability of the sensing domain and the non-invasive nature of the boundary electrodes. A pressure mapping system has been developed in this work that uses a carbon black silicone rubber (CBSR) nanoparticle sensing domain, giving the sensing domain a comparable softness to human skin tissue. To take this technology into a commercial application the performance of such an EIT-based sensor must be quantifiable and repeatable. In this work a series of experiments were repeated for various load locations, strains, and carbon black percentages. Capturing this data gave insight into the how the sensing domain performs over time and captured the transient events limiting the sensor. Metrics were determined to quantify the sensor’s spatial resolution. Load localisation could be determined with error values as low as 0.67 mm. A series of randomised test loads gave similar spatial performance results to the more structured experiments. A quasi-static conductance-force model of the material was developed with an accuracy of ± 0.78 N. One important metric is temporal resolution, as it is the least quantified performance metric in literature, however can be the most important for some applications. For the sensor domains tested, average settling times of between 19.0 – 44.5 s and 22.5 – 36.0 s were determined for 8 and 9 wt% CBSR samples. This sensor platform shows promise for future soft surface pressure mapping applications. Further use of the developed performance metrics will allow for a variety of sensor applications to be validated.