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

Smart mobile applications are driving the demand for higher logic-to-memory bandwidth (BW) in 10–30 GB/s range with lower power consumption and larger memory capacity. This paper presents a radically-different, scalable and lower cost approach than the 3D ICs with TSV stack approach being pursued widely, to achieve high bandwidth. This approach is referred to as interposer approach using ultra-thin glass or silicon with ultra-high I/O density interposers, which does not require TSVs in the logic IC in the 3D stack. This paper presents a comparative study, based on electrical modeling of the logic-to-memory signal path, in various current and emerging package configurations for use in smart mobile devices. Frequency and time domain analysis for each of these scenarios is performed using both chip and package-level models with varying interconnection dimensions. Simulated eye diagrams for the complete data paths in the thin glass interposer approach demonstrated more than 3 Gbps/pin data rate, similar to 3D ICs.

https://www.gtcad.gatech.edu/www/papers/05898516.pdf

Ultra-high I/O density glass/silicon interposers for high bandwidth smart mobile applications

This paper presents the integration of WLAN (2.4 and 5GHz) bandpass filters in glass interposer using through-package vias. The filters include novel embedded passive components such as stitched capacitors with reduced shunt parasitics and via-based inductors that provide area reduction. The filters designed for 2.4 GHz showed an insertion loss of less than 2dB and better than 15dB return loss, while the 5GHz filters showed an insertion loss of less than 1dB with better than 20dB return loss. Stop-band rejection of over 35dB was observed at 2.2 GHz on the 2.4 GHz bandpass filters. The measured results showed good agreement with the simulated values and indicated that the performance on glass interposer closely matches the performance of the more expensive high resistivity silicon with similar properties.

Design and fabrication of bandpass filters in glass interposer with through-package-vias (TPV)

High performance computing systems are driving towards higher clock speeds, more switching circuits, and lower operating voltages. Simultaneous switching noise (SSN) will greatly affect signal integrity in such complex future mixed signal systems. It has been reported that in addition to inductance effects, power plane bounce also becomes a critical factor for packages containing many power and ground vias in parallel. Discrete surface mount capacitors are currently being used by designers to suppress noise. As part of the System on a Package (SOP) concept being developed at the Packaging Research Center (PRC), Georgia Tech, a test vehicle to demonstrate the suppression of SSN using embedded decoupling capacitors is being implemented. This test vehicle uses thin film sequential buildup technology on a low-cost organic platform incorporating polymer-ceramic nanocomposite dielectrics. The design rules for the test vehicle were developed using SOP substrate materials and processes; furthermore, Ansoft along with Matlab were used to model the microstrip transmission lines. The layout was done using Cadence Advanced Package Designer (APD) and output into Gerber format for fabrication. The current test vehicle uses a 300 mm /spl times/300 mm high T/sub g/ FR-5 base substrate with four metal layers on each side. Photoimageable epoxy dry films of 25 /spl mu/m and 75 /spl mu/m thickness were used as the low k (3.4-3.9) sequential build-up dielectric. A novel photoimageable polymer ceramic nanocomposite material developed at the PRC was used for the high k (25-50) thin films. Low cost materials and large area processes were used for the substrate fabrication including dry film printed wiring board (PWB) photoresists, vacuum lamination and spin/meniscus coating for dielectric deposition, full-field UV lithography, and electroless and electrolytic copper metallization. Simulations confirm that the SSN will be suppressed by a factor often when using the high k material as the capacitor dielectric. This paper presents the design, fabrication and validation of embedded decoupling for SOP technology.

/pdf/simultaneous-switching-noise-suppression-for-high-speed-4i6gch07kt.pdf

Simultaneous switching noise suppression for high speed systems using embedded decoupling

A 900-MHz meander planar inverted-F antenna (PIFA) on a magneto-dielectric nanocomposite (MDNC) substrate for mobile communication is presented. Cobalt nanoparticles were synthesized with polymer matrix, and its properties were measured up to 4 GHz. Bandwidth, gain, and radiation efficiency of antenna on different substrates (MDNC, High K material, and FR4) were compared, and it is demonstrated that MDNC is beneficial for antenna miniaturization with acceptable antenna performance. Head effects due to the antenna were studied, and specific absorption rate (SAR) was calculated. The simulation results demonstrate that the MDNC reduces the head effects and the magnetic loss of MDNC helps to decrease SAR due to the antenna.

Magneto-Dielectric Nanocomposite for Antenna Miniaturization and SAR Reduction

Increasing data rates, spectrum efficiency and energy efficiency have been driving major advances in the design and hardware integration of RF communication networks. In order to meet the data rate and efficiency metrics, 5G networks have emerged as a follow-on to 4G, and projected to have 100X higher wireless date rates and 100X lower latency than those with current 4G networks. Major challenges arise in the packaging of radio-frequency front-end modules because of the stringent low signal-loss requirements in the millimeter-wave frequency bands, and precision-impedance designs with smaller footprints and thickness. Heterogeneous integration in 3D ultra-thin packages with higher component densities and performance than with the existing 2D packages is needed to realize such 5G systems. This paper reviews the key building blocks of 5G systems and the underlying advances in packaging technologies to realize them.

Rao Tummala

Papers

Ultra-high I/O density glass/silicon interposers for high bandwidth smart mobile applications

Design and fabrication of bandpass filters in glass interposer with through-package-vias (TPV)

Simultaneous switching noise suppression for high speed systems using embedded decoupling

Magneto-Dielectric Nanocomposite for Antenna Miniaturization and SAR Reduction

A Review of 5G Front-End Systems Package Integration