Measurement Of Pressure Changes Research Articles

Setup Design and Data Evaluation for DEMS in Sodium Ion Batteries, Demonstrated on a Mn‐Rich Cathode Material

AbstractDifferential electrochemical mass spectrometry (DEMS) is a powerful operando method for analyzing side reactions in batteries. We describe our DEMS setup highlighting the relevance for implementing a reference electrode. Although the method provides valuable information, the correct assignment of the DEMS signals to types of gases and quantifying the amounts released can be challenging. A frequent limitation is that gas concentrations are calculated from single m/z ratios. This has the drawback of overlooking unexpected gases which can cause misinterpretation of the signal intensities, or even attributing to gases which are not actually formed. We present a multiple concentration determination (MCD) algorithm that uses the full MS‐spectra, which allows a more reliable determination of the gas release. We demonstrate this approach for Na‐ion half‐cells with P2‐Na0.67Mn3/4Ni1/4O2 (NaMNO) as cathode active material (CAM). Studying the gassing behavior for two electrolyte formulations (1 M NaPF6 in propylene carbonate (PC) and in diglyme (2G)). Against the general belief that glymes lead to more gassing at high potentials, we find that gas evolution for PC electrolytes is larger compared to 2G electrolytes. Dimethyl ether is found to be a decomposition product of 2G. Pressure change measurements are used to independently validate the gas quantification.

Design and Optimization of Piezoelectric Pressure Sensor with AlN as piezo electric material for High-Temperature Application using COMSOL 5.3

Dynamic pressure sensors in contrast to static pressure sensors measure pressure changes in liquids or gases generated due to a blast, a propulsion or an explosion, where the temperature is normally high which is above 700°C[1]. Piezoelectric pressure sensors with their inherent advantage of direct transduction capability are drawing attention for high-temperature applications. Lead Zirconate Titanate (PZT) and Zinc Oxide (ZnO) are popular ferroelectric materials for Piezoelectric sensor applications. Aluminum Nitride (AlN) is a suitable candidate for high-temperature applications with its high melting point of 2673 K, the piezoelectric property remaining stable even up to 1423K, the energy band gap of 6.2eV, piezoelectric coefficient d33 of 7pC/N and pressure handling capacity up to 10 MPa. In this study, COMSOL Multiphysics 5.3 was used to analyse the pressure sensing capability of AlN film by optimizing the crystal orientation and the dimension of AlN in addition to studying suitability of using at high temperature. Also a comparison is done on the high temperature performance of pressure sensor using Silicon and Silicon Carbide as diaphragm.

Oil–water two-phase flow-induced vibration of a cylindrical cyclone with vortex finder

Cylindrical cyclones play an important role in oil–water separation and sewage treatment in the petroleum industry. Here, we describe the characteristics of vibration induced by a two-phase rotational flow in a cylindrical cyclone. The cyclone operating parameters together with a dimensional analysis and multiphase flow numerical simulation were used to understand the flow field characteristics. The frequency and amplitude of pressure fluctuation were obtained by measuring pressure changes at points on the axis of the device. It shows that the pressure in a cylindrical cyclone varies periodically during separation and that fluctuation frequency and amplitude are related to the inlet velocity and flow split ratio. The effect of the overflow split ratio on the pressure fluctuation frequency is negligible, but increasing the overflow split ratio will cause greater fluctuation of the flow. For a cylindrical cyclone, the pressure fluctuation frequency can be calculated from the inlet velocity. Adjusting the inlet velocity and the overflow split ratio changes the mechanical response of the structure. The results of a modal analysis show that the structural vibration response is consistent with the response state of the lowest point of the internal central-vortex pressure and that both are in approximate circular motion. Furthermore, the frequency of pressure fluctuation induced by the flow is close to the intrinsic frequency of the structure with a single bottom constraint, which can cause unwanted resonance easily. Therefore, an appropriately added constraint on a cylindrical cyclone should be taken into consideration to avoid the resonance frequency.

Fluidic innervation sensorizes structures from a single build material.

Multifunctional materials with distributed sensing and programmed mechanical properties are required for myriad emerging technologies. However, current fabrication techniques constrain these materials’ design and sensing capabilities. We address these needs with a method for sensorizing architected materials through fluidic innervation, where distributed networks of empty, air-filled channels are directly embedded within an architected material’s sparse geometry. By measuring pressure changes within these channels, we receive feedback regarding material deformation. Thus, this technique allows for three-dimensional printing of sensorized structures from a single material. With this strategy, we fabricate sensorized soft robotic actuators on the basis of handed shearing auxetics and accurately predict their kinematics from the sensors’ proprioceptive feedback using supervised learning. Our strategy for facilitating structural, sensing, and actuation capabilities through control of form alone simplifies sensorized material design for applications spanning wearables, smart structures, and robotics.

The sialodynamic test: A preliminary porcine head study

ObjectivesTo provide a concept of measuring pressure changes under constant fluid infusion for the diagnosis of sialolithiasis, termed the sialodynamic test, in a porcine head model.MethodsUsing a porcine head model, a constant infusion of water into the submandibular gland of the two groups over 30 s was performed and the outlet pressure was measured. Metal beads were inserted into the salivary duct for obstruction simulation after the normal submandibular gland sialodynamic measurements were completed. Statistical analyses were performed to evaluate the differences between the measured individuals and the experimental group (n = 3).ResultsThe results showed no significant difference between individuals in the control group, but intergroup variation was noted in the simulated sialolithiasis group. The volume-dependent linear increase in pressure was exacerbated in the simulated sialolithiasis group compared with the control.ConclusionThis study indicated that evaluating the relationship between pressure and volume changes can help to determine whether stones are present in the submandibular gland. The sialodynamic test might serve as a potential diagnostic method for salivary diseases.

Simple Pressure Sensor with Highly Customizable Sensitivity Based on Fiber Bragg Grating and Pill-Shaped 3D-Printed Structure

This study presents a simple pill-shaped pressure sensor fabricated by fused deposition modelling (FDM) technology. A fiber Bragg grating (FBG) sensor was embedded inside the structure during the 3D printing process. The dimension of the sensor was simulated by the finite element method to explore the customizability of the pressure sensor. The proposed pill-shaped pressure sensor showed great linearity and achieved high sensitivity with a total Bragg-shifted wavelength of 1.44 nm in the pressure range between 0 and 0.35 MPa, corresponding to a pressure sensitivity of 4.11 nm/MPa. The measured pressure change matched closely with finite element simulation, and the sensitivity could easily increase five times by a thirty percent increase in structure size. The results showed that the pill-shaped pressure sensor had high linearity and great feasibility and could be easily customized to a wide pressure range for static and dynamic pressure measurements in industrial applications.

Shock tube study of natural gas oxidation at propulsion relevant conditions

Global climate change and rising crude oil prices have motivated search of clean, sustainable and economic fuel. Methane, having the highest hydrogen to carbon ratio is ideally the best option towards carbon neutral emissions and reduce greenhouse gas emissions. However, there the economic benefits are minimal when using pure methane because of purification costs. Natural gas primarily consists of methane but with appreciable amounts of C2C4 alkanes which significantly impact oxidation performance, especially when compared to pure methane at high pressures and temperatures, studies of natural gas have been scarce and there is new interest in studying natural gas for its application to propulsion devices. This single pulse shock tube study investigates the effect of natural gas composition on species yields as a function of temperature at various stoichiometric conditions (φ ≈ 0.5, 1.0, 2.0) and high pressure (240 atm) over a nominal reaction time of 2.5 ms. The experimentally measured speciation results for one real natural gas sample from Boise, ID (USA) and a reference natural gas sample are compared to species yield predictions using well established chemical kinetic mechanisms, to check the feasibility of using these mechanisms in the design of propulsion devices. The chemical kinetic simulations are carried out using the constant pressure approach as well as the changing pressure approach which considers the exact measured pressure change in the shock tube. The experiments provide a large speciation data set for optimizing chemical kinetic mechanisms for natural gas applications and to understand the effect of composition on natural gas chemical kinetics. The predictions vary significantly between models tested and effect of composition variation was evident. Aramco Mech 3.0 could predict the experiments almost perfectly, especially at fuel rich conditions.

In vitro circulation model driven by tissue-engineered dome-shaped cardiac tissue

The heart is an essential organ for animals and humans. With the increased availability of pluripotent stem cells, the use of three-dimensional cardiac tissues consisting of cultured cardiomyocytes in in vitro drug evaluation has been widely studied. Several models have been proposed for the realization of the pump function, which is the original function of the heart. However, there are no models that simulate the human circulatory system using cultured cardiac tissue. This study shows that a dome-shaped cardiac tissue fabricated using the cell sheet stacking technique can achieve a heart-like pump function and circulate culture medium, there by mimicking the human circulatory system. Firstly, human induced pluripotent stem cells were differentiated into autonomously beating cardiomyocytes, and cardiomyocyte cell sheets were created using temperature-responsive culture dishes. A cardiomyocyte sheet and a human dermal fibroblast sheet were stacked using a cell sheet manipulator. This two-layered cell sheet was then inflated to create a dome-shaped cardiac tissue with a base diameter of 8 mm. The volume of the dome-shaped cardiac tissue changed according to the autonomous beating. The stroke volume increased with the culture period and reached 21 ± 8.9 μl (n = 6) on day 21. It also responded to β-stimulant and extracellular calcium concentrations. Internal pressure fluctuations were also recorded under isovolumetric conditions by dedicated culture devices. The peak heights of pulsatile pressure were 0.33 ± 0.048 mmHg (n = 3) under a basal pressure of 0.5 mmHg on day 19. When the tissue was connected to a flow path that had check valves applied, it drove a directional flow with an average flow rate of approximately 1 μl s−1. Furthermore, pressure–volume (P–V) diagrams were created from the simultaneous measurement of changes in pressure and volume under three conditions of fluidic resistance. In conclusion, this cardiac model can potentially be used for biological pumps that drive multi-organ chips and for more accurate in vitro drug evaluation using P–V diagrams.

Development of Pt coated SS316 mesh gas diffusion electrodes for a PEM water electrolyzer anode

Cell performance of the polymer electrolyte membrane water electrolyzers is highly depended on the transferred water amount through the cell. Thus, anode gas diffusion electrodes should be selected carefully due to its effect on the overpotentials like mass transfer limitations and ohmic losses inside the cell. In this study, to reduce the cost of polymer electrolyte membrane water electrolyzers systems, stainless steel mesh electrodes (SS316) were used for a cheaper option as an anodic gas diffusion electrode for the polymer electrolyte membrane water electrolyzers. Pressure change measurement experiments were conducted to select the best mesh electrode pore size. In the pressure change measurement experiments, the M1 sample had the lowest pressure drops around 1.02 kPa. After the pressure change experiments, the M1 sample was coated by Pt noble metal in different molar ratios using electrodeposition method, like 1 mM (Case 1), 2 mM (Case 2), and 3 mM (Case 3). At 1.9 V, the current density was improved around 300% compared to the uncoated electrode in Case 3 sample. According to the results, it was seen that the Pt coated stainless steel electrode could be used as an alternative cost-effective gas diffusion electrode in polymer electrolyte membrane water electrolyzer system.

Low-Cost and Highly Sensitive Pressure Sensor with Mold-Printed Multi-Walled Carbon Nanotubes Dispersed in Polydimethylsiloxane.

Flexible pressure sensors with piezoresistive polymer composites can be integrated into elastomers to measure pressure changes in sealings, preemptively indicating a replacement is needed before any damage or leakage occurs. Integrating small percentages of high aspect ratio multi-walled carbon nanotubes (MWCNTs) into polymers does not significantly change its mechanical properties but highly affects its electrical properties. This research shows a pressure sensor based on homogeneous dispersed MWCNTs in polydimethylsiloxane with a high sensitivity region (0.13% kPa, 0–200 kPa) and sensitive up to 500 kPa. A new 3D-printed mold is developed to directly deposit the conductive polymer on the electrode structures, enabling sensor thicknesses as small as 100 μm.

Wearable Intracranial Pressure Monitoring Sensor for Infants.

Monitoring of intracranial pressure (ICP) is important for patients at risk of raised ICP, which may indicate developing diseases in brains that can lead to brain damage or even death. Monitoring ICP can be invaluable in the management of patients suffering from brain injury or hydrocephalus. To date, invasive measurements are still the standard method for monitoring ICP; however, these methods can not only cause bleeding or infection but are also very inconvenient to use, particularly for infants. Currently, none of the non-invasive methods can provide sufficient accuracy and ease of use while allowing continuous monitoring in routine clinical use at low cost. Here, we have developed a wearable, non-invasive ICP sensor that can be used like a band-aid. For the fabrication of the ICP sensor, a novel freeze casting method was developed to encapsulate the liquid metal microstructures within thin and flexible polymers. The final thickness of the ICP sensor demonstrated is 500 µm and can be further reduced. Three different designs of ICP sensors were tested under various pressure actuation conditions as well as different temperature environments, where the measured pressure changes were stable with the largest stability coefficient of variation being only CV = 0.0206. In addition, the sensor output values showed an extremely high linear correlation (R2 > 0.9990) with the applied pressures.

Degradation Mechanism of Lithium-Oxygen Batteries with High Areal Capacity and Lean Electrolyte

Because the nonaqueous Li–O2 batteries are still in their infancy due to numerous problems, there is no report, which actually attained the energy density of 500 Wh/kg in a complete cell level as a rechargeable battery. Except a few works[ref.1-3], almost all studies reported so far included too much excess weight of electrolytes, which results in much lower energy densities than those of LIBs. When the electrolyte amount is decreased to fulfill the energy density of 500 Wh/kg, the cell cannot be cycled. Therefore, it is especially important to quantify the decomposition reactions in Li–O2 batteries under more practical conditions of less electrolyte amount and high areal capacity[ref.4].In previous studies, less attention have been payed about the amounts of Li metal electrode and liquid electrolyte, when they determined cycle life of Li–O2 cells, even though these amounts are the important factors to determine not only energy density but also cycle life. Almost all studies so far have been carried out using a thick Li foil (100–500 μm thick). Because the equivalent weight of Li and graphite are 3860 and 372 mAh/g, respectively, the capacity ratio of negative to positive electrodes (N/P ratio) should be at least less than 3860/372 ≒ 10 to keep the advantage over graphite electrodes. When the areal capacity of the Li metal anode is set to 4 mAh/cm2, the thickness of the Li metal is calculated to be about 20 μm. On the other hand, the electrolyte amount has a more significant influence on the energy density than the Li metal thickness owing to the larger mass density of the electrolyte (1.16 g/cm3) than that of Li metal (0.53 g/cm3). The ratio of the electrolyte volume to the total pore volume of cell components is an important parameter, however, the ratio of electrolyte weight to cell capacity (E/C, gA/h) is empirically used to represent the electrolyte amount in LIBs.10 The E/C ratio in our experiments is 10 gA/h, which is much smaller than those of previous studies (E/C ≥ 50 gA/h).In the present study, we have examined reaction products in a porous carbon positive electrode by using a two-compartment cell design, where anode and cathode compartments were separated by a solid-state Li+ conductor to eliminate possible interference from the reactions at Li metal negative electrode. Because the monitoring the gas consumed/produced during the operation is nearly the only way to determine the CE of the O2 electrode, we used on-line gas analysis as well as pressure change measurements for understanding parasitic reactions coming from electrolyte decomposition. As a result, we clarified that the ratio of electrolyte weight to cell capacity is a good parameter to correlate with cycle life. Only 5 cycles were obtained at an areal capacity of 4 mAh/cm2. When the areal capacity was decreased to half, the cycle life was extended to 18 cycles. However, the total electric charge consumed for parasitic reactions was 35 and 59% at the first and the third cycle, respectively. This surprisingly large amount of parasitic reactions was suppressed by half using redox mediators while keeping a similar cycle life. Based on by-product distribution, we will propose possible mechanisms of TEGDME decomposition.

Manual Cervical Traction and Trunk Stabilization Cause Significant Changes in Upper and Lower Esophageal Sphincter: A Randomized Trial

ObjectivesDysfunctions in the lower esophageal sphincter (LES) and the upper esophageal sphincter (UES) levels can occur owing to poor muscle coordination, contraction, or relaxation. Such condition can possibly be addressed by functional rehabilitation. The aim of this study was to measure pressure changes in the UES and LES at rest and during routine rehabilitation techniques, that is, cervical manual traction and trunk stabilization maneuver. MethodsThis study was conducted in a University Hospital Gastrointestinal Endoscopy Center. Cervical manual traction and a trunk stabilization maneuver were performed in a convenient group of 54 adult patients with gastroesophageal reflux disease. High-resolution manometry was used to measure pressure changes in the LES and UES at rest and during manual cervical traction and trunk stabilization maneuver. ResultsAverage initial resting UES pressure was 90.91 mmHg. A significant decrease was identified during both cervical traction (average UES pressure = 42.13 mmHg, P < .001) and trunk stabilization maneuver (average UES pressure = 62.74 mmHg, P = .002). The average initial resting LES pressure was 14.31 mmHg. A significant increase in LES pressure was identified both during cervical traction (average LES pressure = 21.39 mmHg, P < .001) and during the trunk stabilization maneuver, (average pressure = 24.09 mmHg, P < .001). ConclusionCervical traction and trunk stabilization maneuvers can be used to decrease pressure in the UES and increase LES pressure in patients with gastroesophageal reflux disease.

Towards Accurate Boundary Conditions for CFD Models of Synthetic Jets in Quiescent Flow

In this paper, an accurate model to simulate the dynamics of the flow of synthetic jets (SJ) in quiescent flow is proposed. Computational modeling is an effective approach to understand the physics involved in these devices, commonly used in active flow control for several reasons. For example, SJ actuators are small; hence, it is difficult to experimentally measure pressure changes within the cavity. Although computational modeling is an advantageous approach, experiments are still the main technique employed in the study of SJs due to the lack of accurate computational models. The same aspect that represents an advantage over other techniques also represents a challenge for the computational simulations, such as capturing the unsteady phenomena, localized compressible effects, and boundary layer formation characteristic of this complex flow. One of the main challenges in the simulation of SJs is related to the fact that the spatial and temporal scales of the actuator and the corresponding flow control application differed in several orders of magnitude. Hence, in this study we focus on the use of Computational Fluid Dynamics (CFD) and Reduced Order Models (ROM) to develop an accurate yet low-cost model to capture the complexities of the flow of a SJ in quiescent flow. Numerical results show two possible paths for SJ modeling; (1) to obtain a boundary condition to predict velocity profile and jet formation from experimental data of diaphragm’s deformation; and, (2) to predict peak velocity at the jet’s outlet with a ROM approach and to use the physical details of the actuator to develop an accurate boundary condition for CFD. Both approaches are validated through experimental data available in the literature; good agreement between results from CFD, Lumped Element Model (LEM), and experimental data are achieved. Finally, it was concluded that the coupling between LEM and CFD is a novel and accurate approach, which improves CFD due to the advantages of LEM closing the gap between LEM’s lack of flow detail and CFD’s lack of geometrical/physical information of the actuator.

Numerical modelling of changes of pressure inside the protected room during fighting the fire using carbon dioxide

Purpose This paper aims to study and assess a new approach for prediction of changes of pressure during gas discharge inside the room protected by fixed gaseous extinguishing system by computational fluid dynamics (CFD) simulations. Design/methodology/approach The research program consisted of two stages. The first stage was dedicated to the experimental measurements of pressure changes during extinguishing gas discharge into the test chamber in a real scale (70 m3), for two relief openings that differ in their area. The next step was about performing CFD simulations forecasting pressure changes during gas discharge into the numerically represented test chamber. Estimation of the correctness and usefulness of the CFD model was based on a comparison of the CFD results with standard calculations and experimental measurements. Findings Numerical modelling of pressure changes during the carbon dioxide discharge was very close to the experiment. The obtained results had sufficient accuracy (in most cases relative error &lt;15%), while the standard approach predicted pressure changes with an average relative error over 36% and did not estimate the decrease of pressure at all. Originality/value Conducted research confirms the viability of the new approach in modelling the pressure changes and indicates additional benefits of the numerical analyses in the determination of the fire safety of protected premises.

Probing Changes in Pressure With Subpascal Resolution Using an Optical Fiber Fabry–Perot Interferometer

This article reports a novel optical fiber extrinsic Fabry–Perot interferometer (EFPI) for probing pressure changes with subpascal (~0.1 Pa, $\sim 1.45\times 10^{-5}$ psi) resolution. The principal idea of the sensor is to employ a traditional C-shaped Bourdon tube as a mechanical transducer that is coupled to a highly sensitive EFPI device. The cavity of the EFPI device is formed between a gold-coated mirror, mounted to a concave section of the Bourdon tube, and the endface of an optical fiber mounted at the base section of the Bourdon tube. Based on this design, the pressure-induced deflections of the Bourdon tube are directly correlated with the changes in cavity length of the EFPI, which can be determined by analyzing the interference signals. An experiment based on probing hydrostatic pressure changes induced by the addition of single water droplets to a test chamber was performed to quantify the measurement resolution of the proposed sensor because an apparatus for producing exceedingly small, stable, and reproducible pressure changes does not exist. Compared with conventional optical fiber pressure sensors, the proposed pressure sensor requires a simple fabrication process and can be used to measure pressure changes with high sensitivity ( $\sim 23.5~\mu \text{m}$ /kPa, cavity length change/pressure change). Moreover, the sensitivity and resolution of the pressure sensor can be flexibly adjusted using Bourdon tubes designed for different dynamic ranges (e.g., 0–70 MPa, 0–10152 psi). It is believed that the proposed novel pressure sensor has the potential to find a wide range of applications that require precise instrumentation.

Pressure based MRI-compatible muscle fascicle length and joint angle estimation

BackgroundFunctional magnetic resonance imaging (fMRI) provides critical information about the neurophysiology of the central nervous systems (CNS), posing clinical significance for the understanding of neuropathologies and advancement of rehabilitation. Typical fMRI study designs include subjects performing designed motor tasks within specific time frames, in which fMRI data are then analyzed by assuming that observed functional brain activations correspond to the designed tasks. Therefore, developing MRI-compatible sensors that enable real-time monitoring of subjects’ task performances would allow for highly accurate fMRI studies. While several MRI-compatible sensors have been developed, none have demonstrated the ability to measure individual muscle fascicle length during fMRI, which could help uncover the complexities of the peripheral and central nervous systems. Furthermore, previous MRI-compatible sensors have been focused on biologically intact populations, limiting accessibility to populations such as those who have undergone amputation.MethodsWe propose a lightweight, low-cost, skin impedance-insensitive pressure-based muscular motion sensor (pMMS) that provides reliable estimates of muscle fascicle length and joint angle. The muscular motions are captured through measured pressure changes in an air pocket wrapped around the muscle of interest, corresponding to its muscular motion. The muscle fascicle length and joint angle are then estimated from the measured pressure changes based on the proposed muscle-skin-sensor interaction dynamics. Furthermore, we explore an integration method of multiple pMMS systems to expand the sensor capacity of estimating muscle fascicle length and joint angle. Ultrasound imaging paired with joint encoder measurements are utilized to assess pMMS estimation accuracy of muscle fascicle length in the tibialis anterior (TA) and ankle joint angle, respectively, of five biologically intact subjects.ResultsWe found that a single pMMS sufficiently provides robust and accurate estimations of TA muscle fascicle length and ankle joint angle during dorsiflexion at various speeds and amplitudes. Further, differential pressure readings from two pMMSs, in which each pMMS were proximally and distally placed, were able to mitigate errors due to perturbations, expanding pMMS capacity for muscle fascicle length and ankle joint angle estimation during the full range of plantar flexion and dorsiflexion.ConclusionsOur results from this study demonstrate the feasibility of the pMMS system to further be incorporated in fMRI settings for real-time monitoring of subjects’ task performances, allowing sophisticated fMRI study designs.

Time response characteristics of a highly sensitive barometric pressure change sensor based on MEMS piezoresistive cantilevers

This paper describes the frequency characteristics of a highly sensitive barometric pressure change sensor. Here, we propose a method to measure pressure changes based on microelectromechanical systems piezoresistive cantilevers and an air chamber. The proposed sensor structure realizes a mechanical high pass filter to eliminate the influence of the barometric pressure change due to meteorological variations. The experimental frequency characteristics indicate that the proposed sensor unit with a high resolution of less than 0.1 Pa from 0.1 to 10 Hz responds to pressure changes with a high pass filter property according to the chamber volume size.

Patient-specific 3D-printed coronary models based on coronary computed tomography angiography volumes to investigate flow conditions in coronary artery disease

Background: 3D printed patient-specific coronary models have the ability to enable repeatable benchtop experiments under controlled blood flow conditions. This approach can be applied to CT-derived patient geometries to emulate coronary flow and related parameters such as Fractional Flow Reserve (FFR). Methods: This study uses 3D printing to compare such benchtop FFR results with a non-invasive CT-FFR research software algorithm and catheter based invasive FFR (I-FFR) measurements. Fifty-two patients with a clinical indication for I-FFR underwent a research Coronary CT Angiography (CCTA) prior to catheterization. CT images were used to measure CT-FFR and to generate patient-specific 3D printed models of the aortic root and three main coronary arteries. Each patient-specific model was connected to a programmable pulsatile pump and benchtop FFR (B-FFR) was derived from pressures measured proximal and distal to coronary stenosis using pressure transducers. B-FFR was measured for two coronary outflow rates (‘normal’, 250 ml min−1; and ‘hyperemic’, 500 ml min−1) by adjusting the model’s distal coronary resistance. Results: Pearson correlations and ROC AUC were calculated using invasive I-FFR as reference. The Pearson correlation factor of CT-FFR and B-FFR-500 was 0.75 and 0.71, respectively. Areas under the ROCs for CT-FFR and B-FFR-500 were 0.80 (95%CI: 0.70–0.87) and 0.81 (95%CI: 0.64–0.91) respectively. Conclusion: Benchtop flow simulations with 3D printed models provide the capability to measure pressure changes at any location in the model, for ultimately emulating the FFR at several simulated physiological blood flow conditions. Clinical Trial Registration: https://clinicaltrials.gov/show/NCT03149042

Estimation of viscoelasticity of radial artery via simultaneous measurement of changes in pressure and diameter using a single ultrasound probe

To establish an evaluation index for vascular endothelial function, we developed an ultrasonic probe that can measure changes in blood pressure and blood vessel diameter at the same position in the radial artery. Based on phantom experiments, the pressure waveforms measured using the piezoelectric effect of the ultrasonic probe element and those using a pressure sensor exhibited a high correlation (correlation coefficient: r = 0.979 – 0.999). We confirmed the continuous measurement of the relationship between changes in blood pressure and the diameter from the in vivo experiments. We could then estimate the changes in viscoelasticity by calibrating the output from the probe element to the absolute blood pressure values in advance. The average coefficients of variations were 0.02 and 0.24 for elasticity and viscosity, respectively. This study demonstrated the possibility of measuring changes in the viscoelastic moduli of the radial arterial wall due to flow-mediated dilation using the developed ultrasonic probe.