Rapid and sensitive detection of antibiotic resistance on a programmable digital microfluidic platform.

The widespread dissemination of CTX-M extended spectrum ß-lactamases among Escherichia coli bacteria, both in nosocomial and community environments, is a challenge for diagnostic bacteriology laboratories. We describe a rapid and sensitive detection system for analysis of DNA containing the blaCTX-M-15 gene using isothermal DNA amplification by recombinase polymerase amplification (RPA) on a digital microfluidic platform; active matrix electrowetting-on-dielectric (AM-EWOD). The devices have 16,800 electrodes that can be independently controlled to perform multiple and simultaneous droplet operations. The device includes an in-built impedance sensor for real time droplet position and size detection, an on-chip thermistor for temperature sensing and an integrated heater for regulating the droplet temperature. Automatic dispensing of droplets (45 nL) from reservoir electrodes is demonstrated with a coefficient of variation (CV) in volume of approximately 2%. The RPA reaction is monitored in real-time using exonuclease fluorescent probes. Continuous mixing of droplets during DNA amplification significantly improves target DNA detection by at least 100 times compared to a benchtop assay, enabling the detection of target DNA over four-order-of-magnitude with a limit of detection of a single copy within ~15 minutes.

Potential improvements for dual directional view displays.

Dual directional view (DDV) displays show different images to different viewers. For example, the driver of a car looking at a central DDV display could view navigation information, while the passenger, looking from a different angle, could be watching a movie. This technology, which has now established itself on the dashboards of high-end Jaguar, Mercedes, and Range Rover cars, is manufactured by Sharp Corporation using a well-known parallax barrier technique. Unfortunately parallax barriers are associated with an inevitable drop in brightness compared with a single view display. A parallax barrier-based DDV display typically has less than half the transmission of a single view display. Here we present a solution to these problems via the use of a combined microlens and parallax barrier system, which can not only boost the brightness by 55% from a parallax barrier-only system but increase the head freedom by 25% and reduce crosstalk also. However, the use of microlenses (which must be positioned between the polarizers of the LCD) can adversely affect the contrast ratio of the display. Careful choice of the LCD mode is therefore required in order to create a DDV display that is both high in brightness and contrast ratio. The use of a single-domain vertically aligned nematic (VAN) liquid crystal (LC) mode, together with a microlens plus parallax barrier system can achieve this with a contrast ratio of 1700∶1 measured at 30° to normal incidence.

Formation of a twisted synclinic structure by an antiferroelectric liquid crystal material with strong quadrupolar interlayer coupling.

Following the work of Rudquist et al. [J. Mater. Chem. 9, 1257 (1999)], the thresholdless mode exhibited by some devices filled with some antiferroelectric liquid crystal materials is widely accepted to be due to the formation of a twisted synclinic structure in the device. In this work, we consider under what circumstances this structure forms in preference to the expected anticlinic structure. We show that a strong polar interaction at the surfaces is a necessary but not sufficient condition, and that a strong quadrupolar component of the interlayer interaction is also required. Examination of the stability of the possible ground states reveals a simple explanation for the frequency and temperature dependent electro-optical properties that are observed experimentally, including priming.