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

This work demonstrates, for the first time, implementation of a V-band end-fire Yagi-Uda antenna on an ultra-thin (100um) glass substrate (er =5.3). The quasi Yagi-Uda antenna is chosen because of its small form factor (λ0/2 × λ0/2). The center frequency of the antenna is 53 GHz. The fabricated antenna-on-glass shows good performance with 3.1 dBi of measured gain and 3 GHz of 10-dB impedance bandwidth. H-plane Co-pol and Cross-pol radiation patterns were measured at 53 GHz. All measurements are in close agreement with simulated results.

A V-band end-fire Yagi-Uda antenna on an ultra-thin glass packaging technology

The past, present, and future of multilayer ceramic multichip modules in electronic packaging

Direct Cu-Cu bonding has been pursued by the semiconductor industry as the next interconnection node, for its superior power-handling capability, thermal stability and reliability as compared to traditional solders. However, manufacturability of Cu interconnections has so far been severely limited by the relatively high modulus of Cu, requiring costly planarization processes to address non-coplanarities and warpage to enable bonding in solid-state. This paper introduces a new class of all-Cu interconnections formed by low-temperature sintering of low-modulus nanocopper foams. The physical properties of these foams are tunable with their nanostructure and morphology, giving design flexibility. The proposed nanocopper interconnections have the following advantages: 1) fabrication compatible with standard semiconductor infrastructures and processes, 2) sub-20GPa elastic modulus pre-sintering providing tolerance to non-coplanarities and warpage in assembly, 3) densification at temperatures below 250°C to form high-density all-Cu interconnections, with excellent electrical and thermal properties, and 4) wide applicability from ultra-fine pitch to large-area interconnections for high-power devices. This paper reports the fabrication, characterization and first proof-of-concept demonstration of sintering of such nanocopper interconnections. Nanocopper foams were first synthetized by co-sputtering 2µm Cu25Si75 (at%) thin films on Si(100) substrates, and then electrochemically dealloying the thin-films in hydrofluoric acid under a range of applied voltages. Imaging of the foams by scanning electron microscopy (SEM) confirmed that they consisted of 45nm-sized uniform copper ligaments. Further, native oxides present in the as-synthetized samples were effectively removed with a short etching step in acetic acid, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis, without affecting the foams' nanostructure. Differential scanning calorimetry (DSC) characterization indicated an exothermal peak at 180°C, beyond which coarsening may initiate. Finally, isothermal aging of the nanofoams was carried out in N2 atmosphere at 100 and 300oC range for 180-900sec. No sintering was observed after aging at 150oC, as expected from DSC results, while sintering was confirmed after only 180s at 300oC, with observed densification and shrinkage of the foam, successfully demonstrating the proposed concept. In conclusion, a novel nanocopper foam interconnection technology is demonstrated with the potential to address manufacturability, scalability and cost across consumer, high performance and automotive applications.

Novel High-Temperature, High-Power Handling All-Cu Interconnections through Low-Temperature Sintering of Nanocopper Foams

A process for manufacturing a sealing glass composition consisting essentially of the following ingredients in the following proportions: } Percent by weight }PbO 66.0 }B2O3 14.0 }SiO2 2.0 }Al2O3 3.5 }ZnO 10.5 }CuO 2.5 }Bi2O3 1.

Process for manufacturing low temperature sealing glasses

The various embodiments of the present invention provide a low cost, low electrical loss, and low stress panel-based silicon interposer with TPVs. The interposer of the present invention has a thickness of about 100 microns to 200 microns and such thickness is achieved without utilizing a carrier and further wherein no grinding, bonding, or debonding methods are utilized, therefore distinguishing the interposer of the present invention from prior art embodiments.

Rao Tummala

Papers

A V-band end-fire Yagi-Uda antenna on an ultra-thin glass packaging technology

The past, present, and future of multilayer ceramic multichip modules in electronic packaging

Novel High-Temperature, High-Power Handling All-Cu Interconnections through Low-Temperature Sintering of Nanocopper Foams

Process for manufacturing low temperature sealing glasses

Through package via structures in panel-based silicon substrates and methods of making the same