We present a highly elastic strain gauge based on capacitive sensing of parallel, carbon nanotube-based percolation electrodes separated by a dielectric elastomer. The fabrication, relying on vacuum filtration of single-walled carbon nanotubes and hydrophobic patterning of silicone, is both rapid and inexpensive. We demonstrate reliable, linear performance over thousands of cycles at up to 100% strain with less than 3% variability and the highest reported gauge factor for a device of this class (0.99). We further demonstrate use of this sensor in a robotics context to transduce joint angles.

No abstract

Current molecular diagnostic techniques for susceptibility testing of septicemia rely on genotyping for the presence of known resistance cassettes. This technique is intrinsically vulnerable due to the inability to detect newly emergent resistance genes. Traditional phenotypic susceptibility testing has always been a superior method to assay for resistance; however, relying on the multi-day growth period to determine which antimicrobial to administer jeopardizes patient survival. These factors have resulted in the widespread and deleterious use of broad-spectrum antimicrobials. The real-time PCR antibiogram, described herein, combines universal phenotypic susceptibility testing with the rapid diagnostic capabilities of PCR. We have developed a procedure that determines susceptibility by monitoring pathogenic load with the highly conserved 16S rRNA gene in blood samples exposed to different antimicrobial drugs. The optimized protocol removes heme and human background DNA from blood, which allows standard real-time PCR detection systems to be employed with high sensitivity (<100 CFU/mL). Three strains of E. coli, two of which were antimicrobial resistant, were spiked into whole blood and exposed to three different antibiotics. After real-time PCR-based determination of pathogenic load, a ΔCt<3.0 between untreated and treated samples was found to indicate antimicrobial resistance (P<0.01). Minimum inhibitory concentration was determined for susceptible bacteria and pan-bacterial detection was demonstrated with 3 Gram-negative and 2 Gram-positive bacteria. Species identification was performed via analysis of the hypervariable amplicons. In summary, we have developed a universal diagnostic phenotyping technique that assays for the susceptibility of drug-resistant septicemia with the speed of PCR. The real-time PCR antibiogram achieves detection, susceptibility testing, minimum inhibitory concentration determination, and identification in less than 24 hours.

No abstract

Rapid and precise detection of Chlamydia trachomatis —the leading global cause of sexually transmitted infections (STI)—at the point-of-care (POC) is required for treatment decisions to prevent transmission and sequelae including pelvic inflammatory disease, ectopic pregnancy, tubal-factor infertility and preterm birth. We developed a rapid POC test (POCT), termed LH-POCT, which uses Loop-mediated AMPlification (LAMP) of nucleic acids, and performed a head-to-head comparison with the Cepheid Xpert® CT/NG assay using clinician-collected de-identified paired vaginal samples from a parent study that consecutively enrolled symptomatic and asymptomatic females over age 18 years from the Ministry of Health and Medical Services Health Centers in Fiji. Samples were processed by the Xpert® CT/NG assay and LH-POCT, blinded to the comparator. Discrepant samples were resolved by qPCR. De-identified clinical data and tests for Trichomonas vaginalis , Candida and bacterial vaginosis (BV) were provided. There were a total of 353 samples from 327 females. C. trachomatis positivity was 16.7% (59/353) while the prevalence was 16.82% (55/327) after discrepant resolution. Seven discrepant samples resolved to: four false negatives, two false positives and one true positive for the LH-POCT. The sensitivity of the LH-POCT was 93.65% (95% CI: 84.53% to 98.24%) and specificity 99.31% (95% CI: 97.53% to 99.92%). Discrepant samples clustered among women with vaginal discharge and/or BV. The prototype LH-POCT workflow has excellent performance, meeting many World Health Organization ASSURED criteria for POC tests, including a sample-to-result time of 35 minutes. Our LH-POCT holds promise for improving clinical practice to prevent and control C. trachomatis STIs in diverse health care settings globally.

water droplet dynamics is important across a wide range of disciplines from climate studies to mass spectrometry and biomolecular imaging. Here we describe the creation of an analytical model of evaporation/condensation that accurately predicts water droplet size and temperature over long time scales. We use this analytical model in concert with molecular dynamics simulations of water nano-droplets to understand the dynamics of these small water droplets at the atomic level. We show that the models and assumptions made in the molecular dynamics simulations are robust and in agreement with experiments and our analytical model. The synergism of these two models highlight and capture the important factors involved in evaporation/condensation of water nano-droplets such as curvature. This ability to predict size and temperature and characterize the droplets at the atomic level will allow for the precise manipulation of water droplets as vehicles for biomolecule payloads in x-ray imaging experiments.

Easy trap-and-release of microparticles is necessary to study biological cellular behavior. The hydraulic jump phenomenon inspired us to conceive a microfluidic device for the hydrodynamic trap-and-release of microparticles. A sudden height increase in a microfluidic channel leads to a dramatic decrease in flow velocity, allowing effective trapping of the microparticles by energy conversion. The trapped particles can be released by stronger inertial force based on simply increasing the flow velocity. We present a systematic, numerical study of trap-and-release of the microparticles using multiphase Navier-Stokes equations. Effect of geometry flow velocity, particle diameter, and adhesion force on trap-and-release was studied.