46 The PCB Design Magazine • November 2014
face. Included in this topology are any termina-
tions.
• Stackup planning and the PDN analysis of
a PCB are the two main factors that control the
stability of a design.
In Part 3 next month, I will continue to dis-
cuss signal integrity, in particular where most
designers go wrong with signal integrity and
how to avoid the common pit-falls.
PCBDESIGN
References
1. Barry Olney: Beyond Design: Practical Sig-
nal Integrity, Beyond Design: Pre-Layout Simu-
lation, Intro to Board-Level Simulation and the
PCB Design Process, Beyond Design: Impedance
Matching: Terminations
2. Howard Johnson: High-Speed Signal
Propagation
3. Henry Ott: Electromagnetic Compatibil-
ity Engineering
4. The ICD Stackup and PDN Planner are
distributed globally by www.altium.com
Barry olney is managing direc-
tor of in-Circuit Design Pty ltd
(iCD), australia. This PCB design
service bureau specializes in
board-level simulation, and has
developed the iCD stackup Plan-
ner and iCD PDN Planner software. To read
past columns, or to contact olney, click here.
SIGNAL INTEGRITY, PART 2 continues
beyond design
by Real Time with...
NEPCON South China
a team led by the lawrence livermore scien-
tists has created a new kind of ion channel based
on short carbon nanotubes, which can be insert-
ed into synthetic bilayers and live cell membranes
to form tiny pores that transport water, protons,
small ions, and DNa.
These carbon nanotube "porins" have signifi-
cant implications for future health care and bio-
engineering applications. Nanotube porins even-
tually could be used to deliver drugs to the body,
serve as a foundation of novel biosensors and
DNa sequencing applications, and be used as
components of synthetic cells.
"Many good and efficient
drugs that treat diseases of
one organ are quite toxic
to another," said aleksandr
Noy, an llNl biophysicist
who led the study and is the
senior author on the paper
appearing in Nature. "This is
why delivery to a particular
part of the body and only
releasing it there is much
better."
The lawrence livermore team, together with
colleagues at the Molecular Foundry at the law-
rence Berkeley National laboratory, university of
California Merced and Berkeley campuses, and
university of Basque Country in spain created a
new type of a much more efficient, biocompat-
ible membrane pore channel out of a carbon
nanotube (CNT)--a straw-like molecule that con-
sists of a rolled up graphene sheet.
"Taken together, our findings establish CNT
porins as a promising prototype of a synthetic
membrane channel with inherent robustness
toward biological and chemical challenges
and exceptional biocompatibility that should
prove valuable for bionanofluidic and cellular
interface applications," said Jia geng, a postdoc
who is the first co-author of
the paper.
Kyunghoon Kim, a
postdoc and another co-
author, added: "We also
expect that our CNT po-
rins could be modified
with synthetic 'gates' to
dramatically alter their se-
lectivity, opening up excit-
ing possibilities for their
use in synthetic cells, drug
delivery and biosensing."
Tiny Carbon Nanotube Pores
Make Big Impact
