Point-of-Need Additive Manufacturing in Austere Arctic Environments: An Evaluation of Medical Logistics Requirements and Capabilities Demonstration.

Medical response to military conflicts, natural disasters, and humanitarian crises are challenged by operational logistics with unreliable supply chains, delayed medical evacuation, and compatibility of the disparate medical equipment and consumables. In these environments, stocks of supplies will become more quickly depleted and the need for equipment parts increases secondary to their higher likelihood for failure from overuse. Additive Manufacturing (AM), or 3D printing, at or closer to the point-of-need provides potential solutions to mitigate these logistics challenges. AM's ability to tailor the resultant product through computer design enables real-time modification of a product to meet a specific situation. In this study, we deployed two different 3D printers to an arctic locale to demonstrate the utility of 3D printing and bioprinting in austere environments. Deployment of AM solutions in austere environments will likely impact medical care following natural disasters and conflicts with contested logistics. The work presented here furthers the readiness status of AM for use in austere environments to manufacture medical equipment parts and demonstrates its potential use for tissue engineering and advanced medical treatments in remote environments.

Development of a bioreactor for in-vitro compression cycling of tissue engineered meniscal implants.

Injuries to the meniscus are common and can impair physical activities. Bioprinted meniscal tissue offers an attractive alternative to donor tissue for meniscal repair but achieving the strength of native tissue is a challenge. Here we report the development of a tissue engineering bioreactor designed to apply repetitive force which may lead to an increase in the compressive modulus and durability of bioprinted meniscal tissues. The modular bioreactor system is composed of a sterilizable tissue culture vessel together with a dock that applies and measures mechanical force. The culture vessel allows for simultaneous compression cycling of two anatomically sized menisci. Using a hybrid linear actuator with a stepper motor, the dock can apply up to 300 N of force at speeds up to 20 mm/s, corresponding to the upper limits of anatomical force and motion in the knee. An interchangeable 22 N load cell was mated between the culture vessel and the dock to log changes in force. Both the culture vessel and dock are maintained in a standard cell culture incubator to provide heat and CO2, while the dock is powered and controlled externally using a step motor drive and customized software.

Proof-of-Concept Vacuum Microelectronic NOR Gate Fabricated Using Microelectromechanical Systems and Carbon Nanotube Field Emitters.

This paper demonstrates a fully integrated vacuum microelectronic NOR logic gate fabricated using microfabricated polysilicon panels oriented perpendicular to the device substrate with integrated carbon nanotube (CNT) field emission cathodes. The vacuum microelectronic NOR logic gate consists of two parallel vacuum tetrodes fabricated using the polysilicon Multi-User MEMS Processes (polyMUMPs). Each tetrode of the vacuum microelectronic NOR gate demonstrated transistor-like performance but with a low transconductance of 7.6 × 10-9 S as current saturation was not achieved due to a coupling effect between the anode voltage and cathode current. With both tetrodes working in parallel, the NOR logic capabilities were demonstrated. However, the device exhibited asymmetric performance due to differences in the CNT emitter performance in each tetrode. Because vacuum microelectronic devices are attractive for use in high radiation environments, to test the radiation survivability of this device platform, we demonstrated the function of a simplified diode device structure during exposure to gamma radiation at a rate of 45.6 rad(Si)/second. These devices represent a proof-of-concept for a platform that can be used to build intricate vacuum microelectronic logic devices for use in high-radiation environments.

Shiga Toxin (Stx) Type 1a and Stx2a Translocate through a Three-Layer Intestinal Model.

Shiga toxins (Stxs) produced by ingested E. coli can induce hemolytic uremic syndrome after crossing the intact intestinal barrier, entering the bloodstream, and targeting endothelial cells in the kidney. The method(s) by which the toxins reach the bloodstream are not fully defined. Here, we used two polarized cell models to evaluate Stx translocation: (i) a single-layer primary colonic epithelial cell model and (ii) a three-cell-layer model with colonic epithelial cells, myofibroblasts, and colonic endothelial cells. We traced the movement of Stx types 1a and 2a across the barrier models by measuring the toxicity of apical and basolateral media on Vero cells. We found that Stx1a and Stx2a crossed both models in either direction. However, approximately 10-fold more Stx translocated in the three-layer model as compared to the single-layer model. Overall, the percentage of toxin that translocated was about 0.01% in the epithelial-cell-only model but up to 0.09% in the three-cell-layer model. In both models, approximately 3- to 4-fold more Stx2a translocated than Stx1a. Infection of the three-cell-layer model with Stx-producing Escherichia coli (STEC) strains showed that serotype O157:H7 STEC reduced barrier function in the model and that the damage was not dependent on the presence of the eae gene. Infection of the three-layer model with O26:H11 STEC strain TW08571 (Stx1a+ and Stx2a+), however, allowed translocation of modest amounts of Stx without reducing barrier function. Deletion of stx2a from TW08571 or the use of anti-Stx1 antibody prevented translocation of toxin. Our results suggest that single-cell models may underestimate the amount of Stx translocation and that the more biomimetic three-layer model is suited for Stx translocation inhibitor studies.

Wearable Sensor-Based Detection of Influenza in Presymptomatic and Asymptomatic Individuals.

BACKGROUND: The COVID-19 pandemic highlighted the need for early detection of viral infections in symptomatic and asymptomatic individuals to allow for timely clinical management and public health interventions. METHODS: Twenty healthy adults were challenged with an influenza A (H3N2) virus and prospectively monitored from 7 days before through 10 days after inoculation, using wearable electrocardiogram and physical activity sensors. This framework allowed for responses to be accurately referenced to the infection event. For each participant, we trained a semisupervised multivariable anomaly detection model on data acquired before inoculation and used it to classify the postinoculation dataset. RESULTS: Inoculation with this challenge virus was well-tolerated with an infection rate of 85%. With the model classification threshold set so that no alarms were recorded in the 170 healthy days recorded, the algorithm correctly identified 16 of 17 (94%) positive presymptomatic and asymptomatic individuals, on average 58 hours postinoculation and 23 hours before the symptom onset. CONCLUSIONS: The data processing and modeling methodology show promise for the early detection of respiratory illness. The detection algorithm is compatible with data collected from smartwatches using optical techniques but needs to be validated in large heterogeneous cohorts in normal living conditions. Clinical Trials Registration. NCT04204493.

Cardiac-based detection of seizures in children with epilepsy.

INTRODUCTION: We evaluated a multi-parametric approach to seizure detection using cardiac and activity features to detect a wide range of seizures across different people using the same model. METHODS: Electrocardiogram (ECG) and accelerometer data were collected from a chest-worn sensor from 62 children aged 2-17 years undergoing video-electroencephalogram monitoring for clinical care. ECG data from 5 adults aged 31-48 years who experienced focal seizures were also analyzed from the PhysioNet database. A detection algorithm was developed based on a combination of multiple heart rhythm and motion parameters. RESULTS: Excluding patients with multiple seizures per hour and myoclonic jerks, 25 seizures were captured from 18 children. Using cardiac parameters only, 11/12 generalized seizures with clonic or tonic activity were detected as well as 7/13 focal seizures without generalization. Separately, cardiac parameters were evaluated using electrocardiogram data from 10 complex partial seizures in the PhysioNet database of which 7 were detected. False alarms averaged one per day. Movement-based parameters did not identify any seizures missed by cardiac parameters, but did improve detection time for 4 of the generalized seizures. CONCLUSION: Our data suggest that cardiac measures can detect seizures with bilateral motor features with high sensitivity, while detection of focal seizures depends on seizure duration and localization and may require customization of parameter thresholds.

Feasibility of Mild Traumatic Brain Injury Assessment Based on Cardiovascular Response to Postural Change.

OBJECTIVE: To determine the feasibility of short-term cardiovascular responses to postural change as a screening tool for mild traumatic brain injury (mTBI), using heart rate metrics that can be measured with a wearable electrocardiogram sensor. SETTING: Military TBI clinic. DESIGN: Data collected from active-duty service members who had sustained a medically diagnosed mTBI within the prior 72 hours and from age- and sex-matched controls. Cardiac data collected while participants performed a sequence of postural changes. MAIN MEASURES: Model classification compared with clinical mTBI diagnosis. RESULTS: Cardiac biomarkers of mTBI were identified and logistic regression classifiers for mTBI were developed from different subsets of biomarkers. The best model achieved 90% sensitivity and 69% specificity using data from 2 different postural changes. CONCLUSION: Noninvasive measurement of cardiovascular response to postural change is a promising approach for field-deployable post-mTBI screening.

An analysis of stereotypical motor movements and cardiovascular coupling in individuals on the autism spectrum.

One of the core diagnostic features of autism spectrum disorder (ASD) is engagement in stereotypical motor movements, although the etiology of this repetitive behavior is unknown. Since the 1960s, it has been hypothesized that stereotypical motor movements serve a homeostatic regulation function, and thereby a putative coupling mechanism to cardiovascular arousal. However, to date, surprisingly few reports explicitly assess cardio-somatic coupling and stereotypical motor movements. The present exploratory study investigates coupling of stereotypical body rocking and hand flapping to heart rate and heart rate variability (HRV) in a convenience sample (n = 10) of children and young adults with moderate to profound ASD. Motor movements were recorded via video and three-axis accelerometry, and simultaneous electrocardiographic signals were obtained to determine cardiovascular indices at or around the onset of naturalistically occurring stereotypy. Analysis of the heart rate revealed both repetitive body rocking and hand flapping in particular were found to associate with a strikingly similar cardiovascular pattern of acceleration and deceleration unrelated to physical demands associated with the movements themselves. Furthermore, neither type of stereotypical movement provoked directional change in heart rate variability. The implications of these results and opportunities for future research are discussed.

Automated respiratory sinus arrhythmia measurement: Demonstration using executive function assessment.

Respiratory sinus arrhythmia (RSA) is a quantitative metric that reflects autonomic nervous system regulation and provides a physiological marker of attentional engagement that supports cognitive and affective regulatory processes. RSA can be added to executive function (EF) assessments with minimal participant burden because of the commercial availability of lightweight, wearable electrocardiogram (ECG) sensors. However, the inclusion of RSA data in large data collection efforts has been hindered by the time-intensive processing of RSA. In this study we evaluated the performance of an automated RSA-scoring method in the context of an EF study in preschool-aged children. The absolute differences in RSA across both scoring methods were small (mean RSA differences = -0.02-0.10), with little to no evidence of bias for the automated relative to the hand-scoring approach. Moreover, the relative rank-ordering of RSA across both scoring methods was strong (rs = .96-.99). Reliable changes in RSA from baseline to the EF task were highly similar across both scoring methods (96%-100% absolute agreement; Kappa = .83-1.0). On the basis of these findings, the automated RSA algorithm appears to be a suitable substitute for hand-scoring in the context of EF assessment.

Automated Detection of Repetitive Motor Behaviors as an Outcome Measurement in Intellectual and Developmental Disabilities.

Repetitive sensory motor behaviors are a direct target for clinical treatment and a potential treatment endpoint for individuals with intellectual or developmental disabilities. By removing the burden associated with video annotation or direct observation, automated detection of stereotypy would allow for longer term monitoring in ecologic settings. We report automated detection of common stereotypical motor movements using commercially available accelerometers affixed to the body and a generalizable detection algorithm. The method achieved a sensitivity of 80% for body rocking and 93% for hand flapping without individualized algorithm training or foreknowledge of subject's specific movements. This approach is well-suited for implementation in a continuous monitoring system outside of a clinical setting.

Proof of Concept Coded Aperture Miniature Mass Spectrometer Using a Cycloidal Sector Mass Analyzer, a Carbon Nanotube (CNT) Field Emission Electron Ionization Source, and an Array Detector.

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer's compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified. Graphical Abstract ᅟ.

Biometrics and Policing: A Protocol for Multichannel Sensor Data Collection and Exploratory Analysis of Contextualized Psychophysiological Response During Law Enforcement Operations.

BACKGROUND: Stress experienced by law enforcement officers is often extreme and is in many ways unique among professions. Although past research on officer stress is informative, it is limited, and most studies measure stress using self-report questionnaires or observational studies that have limited generalizability. We know of no research studies that have attempted to track direct physiological stress responses in high fidelity, especially within an operational police setting. The outcome of this project will have an impact on both practitioners and policing researchers. To do so, we will establish a capacity to obtain complex, multisensor data; process complex datasets; and establish the methods needed to conduct idiopathic clinical trials on behavioral interventions in similar contexts. OBJECTIVE: The objective of this pilot study is to demonstrate the practicality and utility of wrist-worn biometric sensor-based research in a law enforcement agency. METHODS: We will use nonprobability convenience-based sampling to recruit 2-3 participants from the police department in Durham, North Carolina, USA. RESULTS: Data collection was conducted in 2016. We will analyze data in early 2017 and disseminate our results via peer reviewed publications in late 2017. CONCLUSIONS: We developed the Biometrics & Policing Demonstration project to provide a proof of concept on collecting biometric data in a law enforcement setting. This effort will enable us to (1) address the regulatory approvals needed to collect data, including human participant considerations, (2) demonstrate the ability to use biometric tracking technology in a policing setting, (3) link biometric data to law enforcement data, and (4) explore project results for law enforcement policy and training.

High-throughput cardiac safety evaluation and multi-parameter arrhythmia profiling of cardiomyocytes using microelectrode arrays.

Microelectrode arrays (MEAs) recording extracellular field potentials of human-induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) provide a rich data set for functional assessment of drug response. The aim of this work is the development of a method for a systematic analysis of arrhythmia using MEAs, with emphasis on the development of six parameters accounting for different types of cardiomyocyte signal irregularities. We describe a software approach to carry out such analysis automatically including generation of a heat map that enables quick visualization of arrhythmic liability of compounds. We also implemented signal processing techniques for reliable extraction of the repolarization peak for field potential duration (FPD) measurement even from recordings with low signal to noise ratios. We measured hiPS-CM's on a 48 well MEA system with 5minute recordings at multiple time points (0.5, 1, 2 and 4h) after drug exposure. We evaluated concentration responses for seven compounds with a combination of hERG, QT and clinical proarrhythmia properties: Verapamil, Ranolazine, Flecainide, Amiodarone, Ouabain, Cisapride, and Terfenadine. The predictive utility of MEA parameters as surrogates of these clinical effects were examined. The beat rate and FPD results exhibited good correlations with previous MEA studies in stem cell derived cardiomyocytes and clinical data. The six-parameter arrhythmia assessment exhibited excellent predictive agreement with the known arrhythmogenic potential of the tested compounds, and holds promise as a new method to predict arrhythmic liability.

In vivo real-time 3-D intracardiac echo using PMUT arrays.

Piezoelectric micromachined ultrasound transducer (PMUT) matrix arrays were fabricated containing novel through-silicon interconnects and integrated into intracardiac catheters for in vivo real-time 3-D imaging. PMUT arrays with rectangular apertures containing 256 and 512 active elements were fabricated and operated at 5 MHz. The arrays were bulk micromachined in silicon-on-insulator substrates, and contained flexural unimorph membranes comprising the device silicon, lead zirconate titanate (PZT), and electrode layers. Through-silicon interconnects were fabricated by depositing a thin-film conformal copper layer in the bulk micromachined via under each PMUT membrane and photolithographically patterning this copper layer on the back of the substrate to facilitate contact with the individually addressable matrix array elements. Cable assemblies containing insulated 45-AWG copper wires and a termination silicon substrate were thermocompression bonded to the PMUT substrate for signal wire interconnection to the PMUT array. Side-viewing 14-Fr catheters were fabricated and introduced through the femoral vein in an adult porcine model. Real-time 3-D images were acquired from the right atrium using a prototype ultrasound scanner. Full 60° × 60° volume sectors were obtained with penetration depth of 8 to 10 cm at frame rates of 26 to 31 volumes per second.

Live volumetric imaging (LVI) intracardiac ultrasound catheter.

The Live Volumetric Imaging (LVI) catheter is capable of real-time 3D intracardiac echo (ICE) imaging, uniquely providing full volume sectors with deep penetration depth and high volume frame rate. The key enabling technology in this catheter is an integrated piezoelectric micromachined ultrasound transducer (pMUT), a novel matrix phased array transducer fabricated using semiconductor microelectromechanical systems (MEMS) manufacturing techniques. This technology innovation may enable better image guidance to improve accuracy, reduce risk, and reduce procedure time for transcatheter intracardiac therapies which are currently done with limited direct visualization of the endocardial tissue. Envisioned applications for LVI include intraprocedural image guidance of cardiac ablation therapies as well as transcatheter mitral and aortic valve repair.

Erratum: Publisher's Note: "High yield fabrication of multilayer polydimethylsiloxane devices with freestanding micropillar arrays" [Biomicrofluidics 7, 056503 (2013)].

[This corrects the article on p. 056503 in vol. 7.].

High yield fabrication of multilayer polydimethylsiloxane [corrected] devices with freestanding micropillar arrays.

A versatile method to fabricate a multilayer polydimethylsiloxane (PDMS) device with micropillar arrays within the inner layer is reported. The method includes an inexpensive but repeatable approach for PDMS lamination at high compressive force to achieve high yield of pillar molding and transfer to a temporary carrier. The process also enables micropillar-containing thin films to be used as the inner layer of PDMS devices integrated with polymer membranes. A microfluidic cell culture device was demonstrated which included multiple vertically stacked flow channels and a pillar array serving as a cage for a collagen hydrogel. The functionality of the multilayer device was demonstrated by culturing collagen-embedded fibroblasts under interstitial flow through the three-dimensional scaffold. The fabrication methods described in this paper can find applications in a variety of devices, particularly for organ-on-chip applications.

Electromechanical performance of piezoelectric scanning mirrors for medical endoscopy.

The electromechanical performance of piezoelectric scanning mirrors for endoscopy imaging is presented. The devices are supported by a single actuating cantilever to achieve a high fill factor, the ratio of mirror area to the combined mirror and actuator area. The largest fill factor devices (74%) achieved 10° mechanical scan range at +/-10V with a 300 µm long cantilever. The largest angular displacement of 30° mechanical scan range was obtained with a 500 µm long cantilever device with a 63% fill factor driven at 40 Vpp. A systematic investigation of device performance (displacement and speed) as a function of fabrication and operational parameters including the stress balance in the cantilever revealed unexpectedly large displacements with lack of inversion at the coercive field. An interpretation of the results is presented based on piezoelectric film domain orientation and clamping with supporting piezoelectric film characterization measurements.

On-chip collection of particles and cells by AC electroosmotic pumping and dielectrophoresis using asymmetric microelectrodes.

The recent development of microfluidic "lab on a chip" devices requiring sample sizes <100 µL has given rise to the need to concentrate dilute samples and trap analytes, especially for surface-based detection techniques. We demonstrate a particle collection device capable of concentrating micron-sized particles in a predetermined area by combining AC electroosmosis (ACEO) and dielectrophoresis (DEP). The planar asymmetric electrode pattern uses ACEO pumping to induce equal, quadrilateral flow directed towards a stagnant region in the center of the device. A number of system parameters affecting particle collection efficiency were investigated including electrode and gap width, chamber height, applied potential and frequency, and number of repeating electrode pairs and electrode geometry. The robustness of the on-chip collection design was evaluated against varying electrolyte concentrations, particle types, and particle sizes. These devices are amenable to integration with a variety of detection techniques such as optical evanescent waveguide sensing.

Sensitivity of cell-based biosensors to environmental variables.

Electrically active living cells cultured on extracellular electrode arrays are utilized to detect biologically active agents. Because cells are highly sensitive to environmental conditions, environmental fluctuations can elicit cellular responses that contribute to the noise in a cell-based biosensor system. Therefore, the characterization and control of environmental factors such as temperature, pH, and osmolarity is critical in such a system. The cell-based biosensor platform described here utilizes the measurement of action potentials from cardiac cells cultured on electrode arrays. A recirculating fluid flow system is presented for use in dose-response experiments that regulates temperature within +/-0.2 degrees C, pH to within +/-0.05 units, and allows no significant change in osmolarity. Using this system, the relationship between the sensor output parameters and environmental variation was quantified. Under typical experimental conditions, beat rate varied approximately 10% per degree change in temperature or per 0.1 unit change in pH. Similar relationships were measured for action potential amplitude, duration, and conduction velocity. For the specific flow system used in this work, the measured environmental sensitivity resulted in an overall beat rate variation of +/-4.7% and an overall amplitude variation of +/-3.3%. The magnitude of the noise due to environmental sensitivity has a large impact on the detection capability of the cell-based system. The significant responses to temperature, pH, and osmolarity have important implications for the use of living cells in detection systems and should be considered in the design and evaluation of such systems.