Bench-top Experiments Research Articles

Design of an Air Suction Wheel-Hole Single Seed Drill for a Wheat Plot Dibbler

Focusing on the problems of the poor filling ability and stability of the mechanical wheat seeder and the complicated structure of the pneumatic seeder, a special air suction wheel-hole single seed drill for remote controlled self-propelled single seed dibbler in wheat plots was designed in this paper. According to the agronomic requirements of precision seeding in wheat plots, the seeding wheel radius was set at 180 mm 16 suction holes. Using the discrete element simulation software EDEM to analyze the seed disturbance effect of different parameter designs, the thickness of seed suction ring was 16 mm, the height of seed suction mouth was 4.5 mm, and the diameter of seed suction cam was 12 mm. Through hydrodynamic simulation, the phase angle of the negative pressure chamber was 280 degrees, positive pressure chamber was 22 degrees, phase angle of the unpressurized interval zone was 20 degrees, thickness of the negative pressure chamber was 24.5 mm, diameter of transition pipe was 17.5 mm and length of the transition pipe was 14.5 mm. Based on the above design parameters, the samples were then processed and benchtop experiments carried out. The results showed that under the best operating parameters, the re-suction index was 0.82%, the leakage index was 6.67%, and the qualified index was 92.41%, which met the design requirements. This study could provide a reference for the design of single-seed dibbling technology in wheat plots.

Influence of sequential stimulation practices on geochemical alteration of shale

Water-based hydraulic fracturing fluids (HFFs) can chemically interact with formation shale, resulting in altered porosity and permeability of the host rock. Experimental investigations of spatial and temporal shale-HFF interactions are helpful in interpreting chemical compositions of the injectate, as well as predicting alteration of hydraulic properties in the reservoir due to mineral dissolution and precipitation. Most bench-top experiments designed to study shale-HFF chemical interactions, either using batch reactors or flow-through setups, are carried out assuming that the acid spearhead has already become mixed with neutral HFFs. During operations, however, HFFs are typically injected according to a sequenced pumping schedule, starting with a concentrated acid spearhead, followed by multiple additions of near-neutral pH HFFs containing chemical amendments and proppant. In this study, we use geochemical modeling to consider whether this pre-mixed experimental protocol provides results directly comparable to a sequential discrete fluid-shale interaction protocol. Our results show that for the batch system, the transient evolution in major ion concentrations is faster with the sequential procedure. After 2 h of reaction time, the two protocols converge to the same aqueous concentrations. In a flow-through geometry, the pre-mixed model predicts extensive chemical alteration close to the injection point but negligible alteration downstream. In contrast, the sequential model predicts mineral reactions over hundreds of meters along the flow path. The extent of shale alteration in the sequential model at a given location depends on shale mineralogy and where the acid spearhead resides during the shut-in period. The predictive model developed in this study can help experimentalists to design bench-top tests and operators to better translate the results of laboratory experiments into practical applications.

Chemo-Mechanics in All Solid State Composite Cathodes

Decarbonization of transportation systems will require a suite of battery technologies depending on the mode and scale. Solid state batteries are an energy dense and non-flammable alternative to conventional batteries and is currently being explored for passenger vehicles and portable electronics1,2. While there is considerable interest in understanding lithium metal anodes for solid state batteries, many significant challenges still exist in solid state cathodes. Solid state cathodes are composites and usually include a combination of active material, solid electrolyte and binder3. The composition, microstructure, and properties of the cathode has significant implications for rate performance, energy density, and lifetime of these systems. Here we examine composite solid state cathodes comprised of argyrodite Li6PS5Cl and LiNi0.8Co0.1Mn0.1O2. We examine how composition and structure influences performance with a specific lens on understanding how chemo-mechanical transformations and buried solid-solid interfaces evolved during cycle operation. In addition we show how external operating conditions (temperature/pressure) influence stress generation in these systems. In this talk we will discuss how we combine novel bench-top experiments with advanced operando x-ray characterization tools to quantify stress and correlate it to structure.[1]Shen, F., Dixit, M. B., Zaman, W., Hortance, N., Rogers, B., & Hatzell, K. B. (2019). Composite electrode ink formulation for all solid-state batteries. Journal of The Electrochemical Society, 166(14), A3182.[2]Hatzell, K. B., & Zheng, Y. (2021). Prospects on large-scale manufacturing of solid state batteries. MRS Energy & Sustainability, 8(1), 33-39.[3]Ren, Y., Hortance, N., & Hatzell, K. (2022). Mitigating Chemo-Mechanical Failure in Li-S Solid State Batteries with Compliant Cathodes. Journal of The Electrochemical Society.

An Augmented Reality-Based Interaction Scheme for Robotic Pedicle Screw Placement.

Robot-assisted surgery is becoming popular in the operation room (OR) for, e.g., orthopedic surgery (among other surgeries). However, robotic executions related to surgical steps cannot simply rely on preoperative plans. Using pedicle screw placement as an example, extra adjustments are needed to adapt to the intraoperative changes when the preoperative planning is outdated. During surgery, adjusting a surgical plan is non-trivial and typically rather complex since the available interfaces used in current robotic systems are not always intuitive to use. Recently, thanks to technical advancements in head-mounted displays (HMD), augmented reality (AR)-based medical applications are emerging in the OR. The rendered virtual objects can be overlapped with real-world physical objects to offer intuitive displays of the surgical sites and anatomy. Moreover, the potential of combining AR with robotics is even more promising; however, it has not been fully exploited. In this paper, an innovative AR-based robotic approach is proposed and its technical feasibility in simulated pedicle screw placement is demonstrated. An approach for spatial calibration between the robot and HoloLens 2 without using an external 3D tracking system is proposed. The developed system offers an intuitive AR–robot interaction approach between the surgeon and the surgical robot by projecting the current surgical plan to the surgeon for fine-tuning and transferring the updated surgical plan immediately back to the robot side for execution. A series of bench-top experiments were conducted to evaluate system accuracy and human-related errors. A mean calibration error of 3.61 mm was found. The overall target pose error was 3.05 mm in translation and in orientation. The average execution time for defining a target entry point intraoperatively was 26.56 s. This work offers an intuitive AR-based robotic approach, which could facilitate robotic technology in the OR and boost synergy between AR and robots for other medical applications.

Design and pre-clinical evaluation of a folding magnetic anastomosis device for minimally invasive surgery

Objective: This work presents the results of Benchtop tests and pre-clinical study of a novel design for a foldable magnetic anastomosis device. The device can be deployed through an endoscope device channel and fold into a ring larger than the deployment port. This new design enables the target application in JJ-anastomosis creation. Material and methods: The folding anastomosis device is constructed from a chain of permanent magnets suspended in a suture weaving inspired by the contact-aided compliant mechanisms. The device was deployed through an endoscope in Benchtop experiments and its expected coupling force was measured in a pull test. A set of experiments was executed during the pre-clinical study, where the device was deployed in the abdomen, to estimate the reliability of deployment and the plausibility of the use in jejuno-jejunal (JJ)- and gastrojejunal (GJ)-anastomosis creation. Results: The presented folding anastomosis device was shown to deploy through an endoscope device channel and a catheter with an inner diameter of 3.2 mm. After deployment the device folds reliably into a ring with an outer diameter of 7–8 mm. The folded device was shown to exhibit a coupling force comparable to similar cases of JJ-anastomosis creation. It is concluded that the presented design of a folding magnetic ring is suitable for select cases of magnetic compression anastomosis where the device is either delivered through a catheter to fold into an anastomosis ring larger than the deployment port or through an endoscopes device channel to allow for convenient visual confirmation of the device during placement.

Towards breath sensors that are self-powered by design.

Piezoelectric materials are widely used to generate electric charge from mechanical deformation or vice versa. These strategies are increasingly common in implantable medical devices, where sensing must be done on small scales. In the case of a flow rate sensor, a sensor’s energy harvesting rate could be mapped to that flow rate, making it ‘self-powered by design (SPD)’. Prior fluids-based SPD work has focused on turbulence-driven resonance and has been largely empirical. Here, we explore the possibility of sub-resonant SPD flow sensing in a human airway. We present a physical model of piezoelectric sensing/harvesting in the airway, which we validated with a benchtop experiment. Our work offers a model-based roadmap for implantable SPD sensing solutions. We also use the model to theorize a new form of SPD sensing that can detect broadband flow information.

Analysis of the absorption kinetics following dermal exposure to large doses of volatile organic compounds

A mathematical method was developed to study the skin penetration of volatile organic compounds (VOCs) after exposure to a high dose of the substance. While closed-form solutions exist to describe the diffusion and evaporation from small amounts, numerical approaches are often implemented to predict dermal transport involving large doses. This work offers a Laplace transform-based method to estimate the time constant and dynamic and steady-state behaviors. First, the process was divided into two stages, separated by the time it took for excess chemicals to be depleted from the skin surface. Series solutions were written for the percutaneous VOC concentration, absorption and evaporation in the first stage. Application of Laplace transform methods yielded transient profiles after the compound dissipated from the surface of the stratum corneum. In addition, the procedure facilitated the calculation of the time constant and steady-state values. The method was validated using benchtop and fume hood experiments conducted with N,N-diethyl-3-methylbenzamide (DEET) and air velocities of 0.165 m/s and 0.72 m/s, respectively. The increase in the flow rate decreased the total amount of VOC absorbed and reduced the period required for the surface fluid to disappear.

Design and Backdrivability Modeling of a Portable High Torque Robotic Knee Prosthesis With Intrinsic Compliance For Agile Activities.

High-performance prostheses are crucial to enable versatile activities like walking, squatting, and running for lower extremity amputees. State-of-the-art prostheses are either not powerful enough to support demanding activities or have low compliance (low backdrivability) due to the use of high speed ratio transmission. Besides speed ratio, gearbox design is also crucial to the compliance of wearable robots, but its role is typically ignored in the design process. This paper proposed an analytical backdrive torque model that accurately estimate the backdrive torque from both motor and transmission to inform the robot design. Following this model, this paper also proposed methods for gear transmission design to improve compliance by reducing inertia of the knee prosthesis. We developed a knee prosthesis using a high torque actuator (built-in 9:1 planetary gear) with a customized 4:1 low-inertia planetary gearbox. Benchtop experiments show the backdrive torque model is accurate and proposed prosthesis can produce 200 Nm high peak torque (shield temperature <60°C), high compliance (2.6 Nm backdrive torque), and high control accuracy (2.7/8.1/1.7 Nm RMS tracking errors for 1.25 m/s walking, 2 m/s running, and 0.25 Hz squatting, that are 5.4%/4.1%/1.4% of desired peak torques). Three able-bodied subject experiments showed our prosthesis could support agile and high-demanding activities.

Products of catalytic oxidative coupling of methane to improve thermal efficiency in natural gas engines

Pretreating natural gas using catalytic oxidative coupling of methane (OCM) produces ethylene and ethane, both species that increase fuel reactivity, thus increasing the potential to expand the operability range of highly efficient compression ignition combustion in natural gas engines. This paper presents the first experimental results on the impact of OCM product species on engine thermal efficiency and operability range. In the work, a benchtop experiment was conducted to generate a product species distribution from OCM over a Sr/La2O3 catalyst. A computational study using known chemical mechanisms was then employed to investigate the laminar flame speed and ignition delay of the OCM-modified fuel. Finally, engine experiments in both spark-ignition and compression-ignition combustion modes were carried out using a variable compression ratio single-cylinder engine. Results from the benchtop catalyst experiments showed that practical fuel conversion for single-pass OCM resulted in 18 % methane conversion, 60 % C2 selectivity, and 10.8 % C2 yield at a molar C/O ratio of 6. After determining realistic fuel blending ratios for engine operation, the numerical simulation results showed that fuel reactivity and ignition delay improved compared to with methane alone, while laminar flame speed decreased due to higher dilution from the presence of inert OCM products. Engine experimental results confirmed that OCM products have an advantage in CI mode due to reduced ignition delay time. The CI operating range was widely expanded, and approximately 9.9% thermal efficiency gain was achieved. By contrast, efficiency in SI mode was reduced when using OCM products due to an increase in combustion duration and retarded combustion phasing.

(Invited, Digital Presentation) Chemo-Mechanics in Lithium Metal Solid State Batteries

Transportation accounts for 23% of energy-related carbon dioxide emissions and electrification is a pathway toward ameliorating these growing challenges. All solid state batteries could potentially address the safety and driving range requirements necessary for widespread adoption of electric vehicles. However, the power densities of all-solid state batteries are limited because of ineffective ion transport at solid|solid interfaces. New insight into the governing physics that occur at intrinsic and extrinsic interfaces are critical for developing engineering strategies for the next generation of energy dense batteries. However, buried solid|solid interfaces are notoriously difficult to observe with traditional bench-top and lab-scale experiments. Understanding material transformations within these interfaces is critical for assessing failure onset and growth mechanisms in solid electrolytes is necessary for high performance solid-state batteries. While phenomenological understanding of failure mechanisms in garnet solid electrolytes exist, limited experimental validation is available. Herein, we examine the two predominant failure mechanisms observed in lithium metal solid state batteries: (1) filament formation, and (2) isolated lithium plating. We combine a suite of ex situ diagnostic techniques with in situ x-ray imaging to probe material transformation and chemo-mechanics and lithium metal-solid-electrolyte interfaces. Operating conditions as well as material processing conditions are discussed.

Co-axial Projective Imaging for Augmented Reality Telementoring in Skin Cancer Surgery.

Telemedicine has the potential to overcome the unequal distribution of medical resources worldwide. In this study, we report the second-generation co-axial projective imaging (CPI-2) system featured with orthotopic image projection for augmented reality surgical telementoring. The CPI-2 system can acquire surgical scene images from the local site, transmit them wirelessly to the remote site, and project the virtual annotations drawn by a remote expert with great accuracy to the surgical field. The performance characteristics of the CPI-2 system are quantitatively verified in benchtop experiments. The ex vivo study that compares the CPI-2 system and a monitor-based telementoring system shows that the CPI-2 system can reduce the focus shift and avoid subjective mapping of the instructions from a monitor to the real-world scene, thereby saving operation time and achieving precise teleguidance. The clinical feasibility of the CPI-2 system is validated in teleguided skin cancer surgery. Our ex vivo and in vivo experiment results imply the improved performance of surgical telementoring, and the clinical utility of deploying the CPI-2 system for surgical interventions in resource-limited settings. The CPI-2 system has the potential to reduce healthcare disparities in remote areas with limited resources.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10439-022-03000-4.

Hydraulic Detrusor for Artificial Bladder Active Voiding.

The gold standard treatment for bladder cancer is radical cystectomy that implies bladder removal coupled to urinary diversions. Despite the serious complications and the impossibility of controlled active voiding, bladder substitution with artificial systems is a challenge and cannot represent a real option, yet. In this article, we present hydraulic artificial detrusor prototypes to control and drive the voiding of an artificial bladder (AB). These prototypes rely on two actuator designs (origami and bellows) based either on negative or positive operating pressure, to be combined with an AB structure. Based on the bladder geometry and size, we optimized the actuators in terms of contraction/expansion performances, minimizing the liquid volume required for actuation and exploring different actuator arrangements to maximize the voiding efficiency. To operate the actuators, an ad hoc electrohydraulic circuit was developed for transferring liquid between the actuators and a reservoir, both of them intended to be implanted. The AB, actuators, and reservoir were fabricated with biocompatible flexible thermoplastic materials by a heat-sealing process. We assessed the voiding efficiency with benchtop experiments by varying the actuator type and arrangement at different simulated patient positions (horizontal, 45° tilted, and vertical) to identify the optimal configuration and actuation strategy. The most efficient solution relies on two bellows actuators anchored to the AB. This artificial detrusor design resulted in a voiding efficiency of about 99%, 99%, and 89%, in the vertical, 45° tilted, and horizontal positions, respectively. The relative voiding time was reduced by about 17, 24, and 55 s compared with the unactuated bladder.

Matched template analysis of continuous wave laser for space debris ranging application

The growth of human-made space debris, sharing the same Earth’s orbital space as active satellites, is a worrying environmental condition. Precise tracking and orbital modelling of space debris are vital to predict potential future collisions with active satellites. This paper investigates a continuous-wave laser ranging method where a bench-top experiment models the reflected amplitude modulated optical signal from a space debris target. The optical signal is digitised and stored to undergo post-digital signal processing using a parameter estimation matched filter approach to estimate the time-varying delay between the target debris and the observing telescope. The experiment investigated two different detection methods, the direct detection of the optical signal and the coherent detection where the optical signal is amplified with a bright local oscillator before signal detection. The experimental results show that the coherent detection method can provide a more precise time-varying delay estimate than the direct detection method due to the improved signal-to-noise ratio. The experimental results also show improved precision in the parameter estimation when using larger portions of the acquired signal’s time series. The experimental results were used to model for a potential space debris application. For example, assuming the received signal power from the target debris is approximately 3.5fW, the time-varying delay of the target debris using the coherent detection method can be estimated with a precision of 1m/s using 2.5s of the acquired signal time series. This is well within the expected minimum time series that can be collected from a space debris target from a single flyover at the telescope site.

Autofluorescence detection and co-axial projection for intraoperative localization of parathyroid gland

BackgroundNear-infrared (NIR) autofluorescence detection is an effective method for identifying parathyroid glands (PGs) in thyroidectomy or parathyroidectomy. Fiber optical probes provide quantitative autofluorescence measurements for PG detection owing to its high sensitivity and high excitation light cut-off efficiency at a fixed detection distance. However, an optical fiber probe lacks the imaging capability and cannot map the autofluorescence distribution on top of normal tissue background. Therefore, there is a need for intraoperative mapping of PGs with high sensitivity and imaging resolution.MethodsWe have developed a fluorescence scanning and projection (FSP) system that combines a scanning probe and a co-axial projector for intraoperative localization and in situ display of PGs. Some of the key performance characteristics, including spatial resolution and sensitivity for detection, spatial resolution for imaging, dynamic time latency, and PG localization capability, are characterized and verified by benchtop experiments. Clinical utility of the system is simulated by a fluorescence-guided PG localization surgery on a tissue-simulating phantom and validated in an ex vivo experiment.ResultsThe system is able to detect indocyanine green (ICG) solution of 5 pM at a high signal-to-noise ratio (SNR). Additionally, it has a maximal projection error of 0.92 mm, an averaged projection error of 0.5 ± 0.23 mm, and an imaging resolution of 748 μm at a working distance ranging from 35 to 55 cm. The dynamic testing yields a short latency of 153 ± 54 ms, allowing for intraoperative scanning on target tissue during a surgical intervention. The simulated fluorescence-guided PG localization surgery has validated the system’s capability to locate PG phantom with operating room ambient light interference. The simulation experiment on the PG phantom yields a position detection bias of 0.36 ± 0.17 mm, and an area intersection over unit (IoU) of 76.6% ± 6.4%. Fluorescence intensity attenuates exponentially with the thickness of covered tissue over the PG phantom, indicating the need to remove surrounding tissue in order to reveal the weak autofluorescence signal from PGs. The ex vivo experiment demonstrates the technical feasibility of the FSP system for intraoperative PG localization with accuracy.ConclusionWe have developed a novel probe-based imaging and navigation system with high sensitivity for fluorescence detection, capability for fluorescence image reconstruction, multimodal image fusion and in situ PG display function. Our studies have demonstrated its clinical potential for intraoperative localization and in situ display of PGs in thyroidectomy or parathyroidectomy.

Design and Preliminary Evaluation of a Wearable Passive Cam-Based Shoulder Exoskeleton

Mechanically passive exoskeletons may be a practical and affordable solution to meet a growing clinical need for continuous, home-based movement assistance. We designed, fabricated, and preliminarily evaluated the performance of a wearable, passive, cam-driven shoulder exoskeleton (WPCSE) prototype. The novel feature of the WPCSE is a modular spring-cam-wheel module, which generates an assistive force that can be customized to compensate for any proportion of the shoulder elevation moment due to gravity. We performed a benchtop experiment to validate the mechanical output of the WPCSE against our theoretical model. We also conducted a pilot biomechanics study (eight able-bodied subjects) to quantify the effect of a WPCSE prototype on muscle activity and shoulder kinematics during three shoulder movements. The shoulder elevation moment produced by the spring-cam-wheel module alone closely matched the desired theoretical moment. However, when measured from the full WPCSE prototype, the moment was lower (up to 30%) during positive shoulder elevation and higher (up to 120%) during negative shoulder elevation compared to the theoretical moment, due primarily to friction. Even so, a WPCSE prototype, compensating for about 25% of the shoulder elevation moment due to gravity, showed a trend of reducing root-mean-square electromyogram magnitudes of several muscles crossing the shoulder during shoulder elevation and horizontal adduction/abduction movements. Our results also showed that the WPCSE did not constrain or impede shoulder movements during the tested movements. The results provide proof-of-concept evidence that our WPCSE can potentially assist shoulder movements against gravity.

Multichannel Wireless Neurosensing System for battery-free monitoring of neuronal activity

Electrical activity recordings are critical for evaluating and understanding brain function. We present a novel wireless, implantable, and battery-free device, namely the Wireless Neurosensing System (WiNS), and for the first time, we evaluate multichannel recording capabilities in vivo. For a preliminary evaluation, we performed a benchtop experiment with emulated sinusoidal signals of varying amplitude and frequency, representative of neuronal activity. We later performed and analyzed electrocortical recordings in rats of evoked somatosensory activity in response to three paradigms: hind/fore limb and whisker stimulation. Wired recordings were used for comparison and validation of WiNS. We found that through the channel multiplexing element of WiNS, it is possible to perform multichannel recordings with a maximum sampling rate of ∼10 kHz for a total of eight channels. This sampling rate is appropriate for monitoring the full range of neuronal signals of interest, from low-frequency population recordings of electrocorticography and local field potentials to high-frequency individual neuronal spike recordings. These in vivo experiments demonstrated that the evoked neuronal activity recorded with WiNS is comparable to that recorded with a wired system under identical circumstances. Analysis of critical parameters for interpreting the somatosensory evoked activity showed no statistically significant difference between the parameters obtained by a wired system versus those obtained using WiNS. Therefore, WiNS can match the performance of more invasive recording systems. WiNS is a groundbreaking technology with potential applications throughout neuroscience as it offers a simple alternative to address the pitfalls of battery-powered neuronal implants.

Comparison of fluid dynamics changes due to physical activity in 3D printed patient specific coronary phantoms with the Windkessel equivalent model of coronary flow

Background3D printing (3DP) used to replicate the geometry of normal and abnormal vascular pathologies has been demonstrated in many publications; however, reproduction of hemodynamic changes due to physical activities, such as rest versus moderate exercise, need to be investigated. We developed a new design for patient specific coronary phantoms, which allow adjustable physiological variables such as coronary distal resistance and coronary compliance in patients with coronary artery disease. The new design was tested in precise benchtop experiments and compared with a theoretical Windkessel electrical circuit equivalent, that models coronary flow and pressure using arterial resistance and compliance.MethodsFive phantoms from patients who underwent clinically indicated elective invasive coronary angiography were built from CCTA scans using multi-material 3D printing. Each phantom was used in a controlled flow system where patient specific flow conditions were simulated by a programmable cardiac pump. To simulate the arteriole and capillary beds flow resistance and the compliance for various physical activities, we designed a three-chamber outlet system which controls the outflow dynamics of each coronary tree. Benchtop pressure measurements were recorded using sensors embedded in each of the main coronary arteries. Using the Windkessel model, patient specific flow equivalent electrical circuit models were designed for each coronary tree branch, and flow in each artery was determined for known inflow conditions. Local flow resistances were calculated through Poiseuille’s Law derived from the radii and lengths of the coronary arteries using CT angiography based multi-planar reconstructions. The coronary stenosis flow rates from the benchtop and the electrical models were compared to the localized flow rates calculated from invasive pressure measurements recorded in the angio-suites.ResultsThe average Pearson correlations of the localized flow rates at the location of the stenosis between each of the models (Benchtop/Electrical, Benchtop/Angio, Electrical/Angio) are 0.970, 0.981, and 0.958 respectively.Conclusions3D printed coronary phantoms can be used to replicate the human arterial anatomy as well as blood flow conditions. It displays high levels of correlation when compared to hemodynamics calculated in electrically-equivalent coronary Windkessel models as well as invasive angio-suite pressure measurements.

Charging of devices for healthcare applications, using ultrasound wireless power

Current wireless powering is frequently accomplished through inductive fields. An alternative for wireless powering systems is via ultrasound. Potential advantages are deeper penetration, delivery through metals, no electronic interference, and beam steerability to correct for misalignment. These characteristics enable ultrasound-based recharging of batteries located within a hermetically sealed enclosure, e.g., an implantable pulse generator (IPG). Another growth area for wireless power delivery is to support healthcare operations, when digital devices used for healthcare delivery need regular charging. Ultrasound Wireless Powering (UWP) is convenient, avoids cable clutter, and is safe. Planar ultrasound transducers operating between 1 and 3 MHz provide a practical compromise between useful directivity and effective propagation range. This talk will describe the development and evaluation of a UWP recharging system operating at 1 MHz transferring up to 100 mA at nominally 4 V, to charge a Li-Ion battery 10–20 mm through tissue. For potential neurostimulator applications, the receiver module was packaged within 1.2 cc inside a 17-cc titanium-IPG. For digital device charging with UWP, benchtop experiments will demonstrate characteristics to power smartphones comparable to the Qi-standard, version 1.0, which is an industry standard for characterizing charging with inductive fields. [Work partially supported by the NIH/NIBIB R43EB019225.]

A biomimetic skin phantom for characterizing wearable electrodes in the low-frequency regime

Advances in the integration of wearable devices in our daily life have led to the development of new electrode designs for biopotential monitoring. Historically, the development and testing of wearable electrodes for the acquisition of biopotential signals has been empirical, relying on experiments on human volunteers. However, the lack of explicit control on human variables, the intra-, and inter-subject variability complicates the understanding of the performance of these wearable electrodes. Herein, phantom mimicking the electrical properties of the skin in the low-frequency range (1–1000 Hz), which has the potential to be used as a platform for controlled benchtop experiments for testing electrode functionality, is demonstrated. The fabricated phantom comprises two layers representing the deeper tissues and stratum corneum. The lower layer of the phantom mimicking deeper tissues was realized using polyvinyl alcohol cryogel (PVA-c) prepared with 0.9% W/W saline solution by a freeze-thaw technique. The properties of the upper layer representing the stratum corneum were simulated using a 100 µm thick layer fabricated by spin-coating a mixture of polydimethylsiloxane (PDMS), 2.5% W/W carbon black (CB) for conductance, and 40% W/W barium titanate (BaTiO3) as a dielectric. The hydration of the stratum corneum was modeled in a controlled way by varying porosity of the phantom’s upper layer. Impedance spectroscopy measurements were carried out to investigate the electrical performance of the fabricated phantom and validated against the impedance response obtained across a physiological skin impedance range of five human subjects. The results indicated that the Bode plot depicting the impedance response obtained on the phantom was found to lie in the human skin range. Moreover, it was observed that the change of porosity provides control over the hydration and the phantom can be tuned as per the skin ranges among different individuals. Also, the phantom was able to mimic the impact of dry and hydrated skin on a simulated ECG signal in the time domain. The developed skin phantom is affordable, fairly easy to manufacture, stable over time, and can be used as a platform for benchtop testing of new electrode designs.

RVEX: Right Ventricular External Device for Biomimetic Support and Monitoring of the Right Heart

AbstractRight ventricular (RV) failure remains a significant burden for patients with advanced heart failure, especially after major cardiac surgeries such as implantation of left ventricular assist devices. Device solutions that can assist the complex biological function of heart muscle without the disadvantages of bulky designs and infection‐prone drivelines remain an area of pressing clinical need, especially for the right ventricle. In addition, devices that incur contact between blood and artificial surfaces mandate long‐term use of blood‐thinning medications, carrying increased risks for the patients. This work describes the design of a biomimetic, elastic sleeve to support RV‐specific motion via tuned regional mechanical properties. The RV external device (RVEX) in computational models as well as benchtop models and ex vivo (i.e., explanted heart) setups are evaluated to characterize the device and predict functional benefit. Additionally, long‐term implantation potential is demonstrated in mice. Finally, the ability to sensorize the RVEX device to yield resistive self‐sensing capabilities to continuously monitor ventricular deformation, as demonstrated in benchtop experiments and in live animal surgeries, is proposed.