MEMS Electrostatic Actuation in Conducting Biological Media

We present design and experimental implementation of electrostatic comb-drive actuators in solutions of high conductivity relevant for biological cells. The actuators are operated in the frequency range 1-10 MHz in ionic and biological cell culture media, with ionic strengths up to 150 mmol/L. Typical displacement is 3.5 mum at an applied peak-to-peak signal of 5 V. Two different actuation schemes are presented and tested for performance at high frequency. A differential drive design is demonstrated to overcome the attenuation due to losses in parasitic impedances. The frequency dependence of the electrostatic force has been characterized in media of different ionic strengths. Circuit models for the electric double layer phenomena are used to understand and predict the actuator behavior. The actuator is integrated into a planar force sensing system to measure the stiffness of cells cultured on suspended structures.     

Secure and Robust Error Correction for Physical Unclonable Functions

Editor's note:Physical unclonable functions (PUFs) offer a promising mechanism that can be used in many security, protection, and digital rights management applications. One key issue is the stability of PUF responses that is often addressed by error correction codes. The authors propose a new syndrome coding scheme that limits the amount of leaked information by the PUF error-correcting codes.—Farinaz Koushanfar, Rice University     

Enhancement of bending strain tolerance and current carrying property of MgB2 based multifilamentary wires

The effect of bending strain on current carrying capacity of MgB₂ multifilamentary wires was studied with 4, 8 and 16 multifilamentary wires. The critical current density (J_C) of straight wires and bent wires with 5, 10, and 15 cm diameter was measured. Both annealed & bent and bent & annealed wires were used for measurement. The J_C of annealed & bent wires were found to decrease with decrease in bent diameter and the rate of degradation of J_C decreased with increasing number of filaments, while bent & annealed wires almost retained its J_C at all diameters studied.     

Design of XNBR nanocomposites for underwater acoustic sensor applications: Effect of MWNT on dynamic mechanical properties and morphology

In this work, application of rubber‐MWNT nanocomposite for underwater acoustic sensors is explored. The nanocomposite is developed by incorporating multiwalled carbon nanotubes (MWNT) into carboxylated nitrile rubber by mechanical mixing. The addition of MWNT up to 10 phr is found to result in about 330% increase in tensile strength, 140% increase in modulus, and 160% increase in tear strength. Transmission electron microscopy and scanning electron microscopy analyses indicate uniform dispersion of nanotubes in the rubber matrix. Dynamic mechanical analysis shows that damping at ambient temperature gradually increases with increasing filler content. This is attributed to the augmented frictional energy loss at the interface. The damping peak position shifts upward with increase in MWNT concentration, which may be gainfully used to tune to the operational frequency range of underwater acoustic sensors. Payne effect is observed at higher filler concentration due to the breakage of aggregates formed by filler–filler interaction. The nanocomposite may find application for damping structural vibrations and thus to improve the performance of underwater acoustic sensors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40752.     

Concrete made from ceramic industry waste: Durability properties

Concrete which contains waste products as aggregate is called ‘Green’ concrete. Use of hazardous waste in concrete-making will lead to green environment and sustainable concrete technology and so such concrete can also be called as ‘Green’ concrete. Concrete made with ceramic electrical insulator waste as coarse aggregate shows good workability, compressive, tensile and flexural strengths and modulus of elasticity. Further, study of its durability will ensure greater reliability in its usage. Permeation characters are used widely to quantify durability properties of concrete. This paper presents an experimental investigation on the permeation characteristics [volume of voids and water absorption (ASTM C642-06), chloride penetration (ASTM C1202-10), and sorption] of concrete with ceramic electrical insulator waste coarse aggregate (hereafter it is called recycled aggregate concrete) of six different water–cement ratios in comparison with those of corresponding conventional concrete mixes. From the results it has been observed that there is no significant change in the basic trend of permeation characteristics of this recycled aggregate concrete when compared to the conventional concrete. This recycled aggregate concrete possesses higher permeation characteristic values than those of conventional concrete. These values decrease with decrease in water–cement ratio for both the recycled aggregate concrete and the conventional concrete.     

Activating the community for nutritional improvement

This presentation provides information on community-oriented action research conducted under the leadership of Dr. Rajammal P. Devadas, the recipient of the IUNS International Nutrition Award for 2001. Educating, activating, and energizing the community with empowerment have been the focus of the action-oriented research. In the four decades of work presented, massive efforts have been made in the areas of infant and preschool child nutrition; nutritious noon meal programs for children; integration of nutrition, health, and sanitation concepts in the primary school curriculum; use of local foods to eradicate malnutrition; introduction of novel and underexploited foods; food-based approaches to overcome micronutrient malnutrition; equipping women for food and nutrition security; and nutrition education. These efforts have been activated through development of relevant food and educational materials, their introduction to the community, impact evaluation, follow-up, and implementation of the concepts in relevant national programs with massive training efforts. Many of the efforts outlined have formed the basis for regional and nationwide nutrition intervention strategies. The experiences gained and training efforts developed have gone beyond the country-level exposure to training and equipping nutrition workers in other countries.     

Independent testing and validation of prototype hydrogen sensors

In this article, the independent testing and validation of a packaged, electrochemical prototype hydrogen sensor at the National Renewable Energy Laboratory (NREL) is reported. Custom electronics were developed to be compatible with the data acquisition system at NREL. The specialized hydrogen sensor-testing laboratory at NREL used a variety of standardized test protocols to assess sensor performance. The system controlled and monitored humidity, pressure, and hydrogen gas concentration and introduced interference gases such as methane, carbon dioxide, carbon monoxide and ammonia.