Direct measurement of the mechanism by which magnesium specifically modifies the mechanical properties of DNA.

We examine the effect of physiological cations Na+, K+, Mg2+, and Ca2+ on the mechanical properties of bundles of λ-phage DNA using silicon nanotweezers (SNTs). Integrating SNTs with a microfluidic device allows us to perform titration experiments while measuring the effect in real-time. The results show that only for Mg2+ and in particular, at the intra-nuclear concentration (100 mM), the interaction occurs.

Ballistic thermal conductance of a lab-in-a-TEM made Si nanojunction.

The thermal conductance of a single silicon nanojunction was measured based on a Lab-in-a-TEM (microelectromechanical systems in a transmission electron microscope) technique and was found to be at least 2 orders of magnitude larger than the ones of long nanowires in the 380-460 K temperature range. The predominance of ballistic phonon transport appears as the best hypothesis to retrieve quantitative predictions despite the geometrical irregularity of the junction. The measurement is based on a MEMS structure including an electrostatic actuator that allows producing nanojunctions with the accuracy based on the resolution of a transmission electron microscope. The thermal conductance is measured by two integrated resistors that are simultaneously heating and measuring the local temperatures at the nearest of the nanojunction. The considerable thermal conductance of short nanojunctions constitutes a new key element in the design of nanosystems and in the understanding of the damaging of mechanical micronanocontacts. This conducting behavior is also paving the way for the development of nanoscale cooling devices as well as of the recent phononic information technology.

Effect of substrate wettability in liquid dielectrophoresis (LDEP) based droplet generation: theoretical analysis and experimental confirmation.

The generation of droplets for biological reactions at the microscale can be achieved by many techniques, among which the so-called liquid dielectrophoresis technique (LDEP). This is not a new process, but the parameters influencing actuation voltage still need further insight: size and geometry (electrodes width and gap, dielectric thickness), materials (dielectric constant), liquids (surface tension, dielectric constant, conductivity), working conditions (voltage, frequency) and substrate wettability (contact angle). This large experimental space is firstly reduced using non dimensional numbers and then studied in a systematic way thanks to the design of experiments. The contact angle influence is explained thanks to a new analytical model. To summarize, this paper recalls analytical models used to predict the voltage threshold required to develop a liquid rivulet from a mother drop, taking the contact angle into account and providing a large set of experimental results.

Microwave based nanogenerator using the ratchet effect in Si/SiGe heterostructures.

Ratchet based microwave current generators and detectors were developed in Si/SiGe heterostructures for wireless communication with the possibility of extending the detection limit to the terahertz range. A microwave induced ratchet current was generated in the two-dimensional electron gas by patterning an array of semicircular antidots in hexagonal geometry. The spatial asymmetry created by the semicircular antidots forces the electrons under the influence of the microwave electric field to move preferentially towards the direction of the semidisc axis. A photovoltage of the order of few millivolts was observed. Such a photovoltage was completely absent in a symmetric system consisting of circular antidots. The induced photovoltage increased monotonically with microwave power and was found to be independent of the microwave polarization. This device opens the possibility of employing silicon based heterostructures for nanogenerators and other wireless communication devices using microwaves.