44 DESIGN007 MAGAZINE I MAY 2018
4. Understanding Common-Mode Noise, by
Pulse Electronics.
5. High-Speed Signal Propagation, by How-
ard Johnson.
Barry Olney is managing director of
In-Circuit Design Pty Ltd (iCD), Aus-
tralia, a PCB design service bureau
that specializes in board-level
simulation. The company developed
the iCD Design Integrity software
incorporating the iCD Stackup, PDN and CPW Planner. The
software can be downloaded from www.icd.com.au. To
contact Olney, or read past columns, click here.
ground voltage that drives the antennae at
the source. PDN noise is the main driver of
radiated emissions.
• The goal of a low impedance PDN is real-
ized by minimizing the spacing between
the power and ground planes and by using
low impedance decoupling capacitors with
low inductance mounting.
DESIGN007
References
1. Barry Olney's Beyond Design columns:
Return Path Discontinuities, Uncommon Sense-
Differential Pairs, Stackup Planning Parts 1-4.
2. Electromagnetic Compatibility Engineer-
ing, by Henry Ott.
3. What is Differential and Common-Mode
Current? by Ron Brewer.
U of T Engineering researchers have developed a hand-
held 3D skin printer that deposits even layers of skin tissues
to cover
and heal deep wounds. The team believes it to be
the first device that forms tissue in situ, depositing and set
-
ting in place in two minutes or less.
Their research, led by Navid Hakimi (MIE PhD candidate)
under the supervision of Professor Axel Guenther (MIE,
IBBME), and in collaboration with Dr. Marc Jeschke, director
of the Ross-Tilley Burn Centre at Sunnybrook Hospital, was
recently published in the Journal Lab on a Chip.
For patients with deep skin wounds, all three skin lay-
ers—the epidermis, dermis and hypodermis—may be heav-
ily damaged. The current preferred treatment is called
split-thickness skin gr
afting, where
healthy donor skin is
grafted into the surface epidermis and part of the underly
-
ing dermis.
Split-thickness grafting on large wounds requires enough
healthy donor skin to traverse all three layers, and sufficient
graft skin is rarely available. This leaves a portion of the
wounded area ungrafted or uncovered, leading to poor heal
-
ing outcomes.
Although a large number of
tissue-engineered skin
substitutes exist, they are not yet widely used in clinical
settings.
The handheld skin printer resembles a
white-out tape dispenser — except the tape roll
is replaced by a microdevice that forms tissue
sheets. Vertical stripes of "bio ink," made up
of protein-based biomaterials including colla
-
gen, the most abundant protein in the dermis,
and fibrin, a pr
otein
involved in wound healing,
run along the inside of each tissue sheet. The
handheld device is the size of a small shoe box
and weighs less than a kilogram.
The researchers hope that one day they
can begin running clinical trials on humans,
and eventually revolutionize burn care.
"Several steps are needed, but we are con
-
fident we will get there," says Guenther.
Researchers Develop Handheld 3D Skin Printer
