There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Shape-memory polymers

Nanodevices don't use much energy, and if the little they do need can be scavenged from vibrations associated with foot steps, heart beats, noises and air flow, a whole range of applications in personal electronics, sensing and defence technologies opens up. Energy gathering of that type requires a technology that works at low frequency range (below 10 Hz), ideally based on soft, flexible materials. A group working at Georgia Institute of Technology has now come up with a system that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing their associated nanowires together, mechanical energy is converted into electricity via a coupled piezoelectric-semiconductor process. This work shows a potential method for creating fabrics which scavenge energy from light winds and body movement. A self-powering nanosystem that harvests its operating energy from the environment is an attractive proposition for sensing, personal electronics and defence technologies1. This is in principle feasible for nanodevices owing to their extremely low power consumption2,3,4,5. Solar, thermal and mechanical (wind, friction, body movement) energies are common and may be scavenged from the environment, but the type of energy source to be chosen has to be decided on the basis of specific applications. Military sensing/surveillance node placement, for example, may involve difficult-to-reach locations, may need to be hidden, and may be in environments that are dusty, rainy, dark and/or in deep forest. In a moving vehicle or aeroplane, harvesting energy from a rotating tyre or wind blowing on the body is a possible choice to power wireless devices implanted in the surface of the vehicle. Nanowire nanogenerators built on hard substrates were demonstrated for harvesting local mechanical energy produced by high-frequency ultrasonic waves6,7. To harvest the energy from vibration or disturbance originating from footsteps, heartbeats, ambient noise and air flow, it is important to explore innovative technologies that work at low frequencies (such as <10 Hz) and that are based on flexible soft materials. Here we present a simple, low-cost approach that converts low-frequency vibration/friction energy into electricity using piezoelectric zinc oxide nanowires grown radially around textile fibres. By entangling two fibres and brushing the nanowires rooted on them with respect to each other, mechanical energy is converted into electricity owing to a coupled piezoelectric–semiconductor process8,9. This work establishes a methodology for scavenging light-wind energy and body-movement energy using fabrics.

http://www.nanoscience.gatech.edu/zlwang/paper/2008/08_nat_1.pdf

Microfibre–nanowire hybrid structure for energy scavenging

The lateral and vertical integration of ZnO piezoelectric nanowires allows for voltage and power outputs sufficient to power nanowire-based sensors.

http://www.nanoscience.gatech.edu/zlwang/paper/2010/10_NN_01.pdf

Self-powered nanowire devices.

Fundamentals, processes and applications of high-permittivity polymer–matrix composites

Disclosed is a ceramic substrate having a protective coating on at least one surface thereof which includes: a ceramic substrate having at least one electrically conductive via extending to a surface of the substrate; an electrically conductive I/O pad electrically connected to at least one of the vias; an I/O pin brazed to the I/O pad, the brazed pin having a braze fillet; and a protective layer of polymeric material fully encapsulating the I/O pad, wherein the layer of polymeric material protects the I/O pad from corrosion. Also disclosed is a method of protecting a ceramic substrate from corrosion, the ceramic substrate of the type having a plurality of electrically conductive vias extending to a surface of the substrate, a multilayer metallic I/O pad electrically connected to at least one of the vias, and an I/O pin brazed to the I/O pad, the brazed pin having a braze fillet, the method comprising the step of: encapsulating fully the I/O pad with a protective layer of polymeric material, wherein the layer of polymeric material protects the I/O pad from corrosion. In a preferred embodiment, the I/O pin is selectively exposed to plasma ashing to remove any errant polymeric material from the pin shank, thereby assuring electrical contact to the pin shank.

Ceramic substrate having a protective coating thereon and a method for protecting a ceramic substrate

Copper is an excellent candidate material for next generation of chip-package interconnections because of its high electrical and thermal conductivities, good mechanical properties at assembly and operating temperatures and well-established infrastructure to integrate with back-end processes with electroplating technology downscalable to nanoscale. This technology can also accommodate the increasing I/O density of future microprocessors with the best electrical and mechanical performance. In addition, embedment of active components with chip-last approach being proposed by Georgia Tech PRC can also be realized with the shortest interconnections resulting in performance and miniaturization comparable to chip-first approach. There is an increasing trend to replace solders with copper because of these advantages. In this paper, we describe the current status of copper bumping and copper interconnection and assembly technologies and show our future strategy.

Copper interconnections for high performance and fine pitch flip chip digital applications and ultra-miniaturized RF module applications

In this work, a colloidal technique is used to improve the dielectric properties of nanocomposite materials and to achieve thin film deposition (<5 /spl mu/m) on large area substrates using meniscus coating. Using this technique, improved particle dispersion is achieved, which in turn allows for higher volume loading (increased dielectric constant), small variation of dielectric constant across the substrate, and thin-film deposition with lower particle-induced defects. Appropriate dispersants and fillers particularly applicable to meniscus coating of these composite materials were found which allowed the coated and cured composite material to attain high relative dielectric constant (typical 40). Non-meniscus-coated samples with dielectric constants as high as 74 were achieved by varying the particle size distribution.

Improvements and recent advances in nanocomposite capacitors using a colloidal technique

Epoxy Nanocomposite Capacitors for Application as MCM-L Compatible Integral Passives

The advanced packaging technologies that can be expected in the 1990s in high-performance systems are discussed in terms of chip connection, power distribution, heat removal, and thick- and thin-film wiring and package interconnections. The following topics are discussed in detail: (1) chip-level connection providing the required connections between the chip and the package; (2) power distribution to the chip and heat removal from the chip; (3) first-level packages providing all the necessary wiring, interconnections, and power distribution; (4) first-to-second level interconnections; and (5) second-level packages providing all the necessary wiring, connections, power distribution, and power supply connection. >

Rao Tummala

Papers

Ceramic substrate having a protective coating thereon and a method for protecting a ceramic substrate

Copper interconnections for high performance and fine pitch flip chip digital applications and ultra-miniaturized RF module applications

Improvements and recent advances in nanocomposite capacitors using a colloidal technique

Epoxy Nanocomposite Capacitors for Application as MCM-L Compatible Integral Passives

Electronic packaging in the 1990s-a perspective from America