International audienceThis paper presents a microfluidic device that implements standing surface acoustic waves in order to handle single cells, droplets, and generally particles. The particles are moved in a very controlled manner by the two-dimensional drifting of a standing wave array, using a slight frequency modulation of two ultrasound emitters around their resonance. These acoustic tweezers allow any type of motion at velocities up to few 10mm/s, while the device transparency is adapted for optical studies. The possibility of automation provides a critical step in the development of lab-on-a-chip cell sorters and it should find applications in biology, chemistry, and engineering domains

We report on a simple process to fabricate electrohydrodynamic spraying devices with superhydrophobic nozzles. These devices are useful, among other things, in mass spectrometry and printing technology. The superhydrophobic nozzle is created by roughening the surface of the polyfluorotetraethylene (PTFE) by argon and oxygen plasma treatment. We have developed a polymer-based electrospray device with a flat, superhydrophobic nozzle capable of maintaining a high contact angle and stable jetting.

Articles you may be interested inEffect of viscosity, electrical conductivity, and surface tension on direct-current-pulsed drop-on-demand electrohydrodynamic printing frequency

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Electrohydrodynamic (EHD) spraying has been utilized in applications varying from micro-colloid thrusters to technology for film deposition and inkjet printing. Recently, EHD inkjet heads were developed to facilitate the fabrication of printed electronics such as digital displays, printed circuit boards (PCBs), and solar cells. Here, we report the fabrication and application of nanoscale nozzles for EHD inkjet printing. The nozzles were fabricated by depositing an electrically conductive layer on either the inside or outside of quartz micropipettes with sub-micron diameter tips. With the drop-on-demand control needed for inkjet heads, our nanoscale nozzles dispensed silver droplets in fine patterns on glass substrates.

The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and the meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Based on this in-depth study of the meniscus behavior under various signals, the optimal signal is implemented to an EHD inkjet head for drop-on-demand operation. For applied ac voltage and ac voltage superimposed on dc voltage, the jetting phenomenon is a dynamic process due to sequential opposite sign signals. The jetting occurs at the end of the oscillation cycle, where the meniscus oscillates upward and arrives at its highest position.

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The current generation of ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs) operate in the Very-High-Energy (VHE) domain from ∼ 100 GeV to ∼ 100 TeV. They use electronic digital trigger systems to discern the Cherenkov light flashes emitted by Extensive Air Shower (EAS), from the overwhelming Light of the Night Sky (LoNS) background. Near the telescope energy threshold, the number of emitted Cherenkov photons by gamma-ray induced EAS is comparable to the fluctuations of the LoNS and the photon distribution at the Cherenkov-imaging camera plane becomes patchy. This results in a severe loss of effectiveness of the digital triggers. A stereoscopic analog trigger system has been developed for improving the detection capabilities of the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes at the lowest energies. It is based on the analog sum of the photosensor electrical signals. In this paper, the architectural design, technical performances, and configuration of this stereoscopic analog trigger, dubbed "Sum-Trigger-II", are described.