Mechanical Technology March 2015

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40 Mechanical Technology — March 2015
⎪ Nota bene ⎪
Index to advertisers
Aesseal. ...............................2, 14
Air Liquide................................34
Becker Mining South Africa.........25
BMW......................................IBC
Clyde Bergemann Africa.............27
Metso Minerals. ........................26
Verder Pumps. ..........................17
Weir Minerals................. OFC, OBC
Xylem Water Solutions.............. IFC
Yaskawa...................................30
Zest Weg Group.........................22
2KG Training........................12,13
Industry diary
April 2015
4 th Annual Concentrated Solar
Thermal Power Conference &
Exhibition
CSP Today South Africa 2015
14-15 April, Cape Town
Brandon Páramo
May 2015
SME Pressure Vessels Section VIII
Division 1 (3 Day)
4-6 May
Johannesburg, Cedar Park Hotel
Phindi Mbedzi:+27 11 325 0686
Fundamentals to Energy
Management Training
4-6 May, Johannesburg
Thieda Ferreira, Energy Training
Foundation
+27 41 582 2043
Polyvinylidene fluoride piezoelectric
film (PVDF) is a relatively new
class of piezo-electric device.
PVDF is a thin plastic polymer sheet
with its molecules aligned in a uniform
pattern. It has an electrically conductive
coating (eg, graphene) deposited on each
side of the sheet. When an electrical cur-
rent from a sound source is applied to
opposing sides of the material, a converse
piezoelectric effect causes the PVDF film
to distort and vibrate. This vibration is
transferred to the air as a sound wave.
To use PVDF material, an electrical
connection to these conductive coatings
is needed. Soldering directly to the film
is not possible because the heat would
destroy the underlying plastic PVDF
material. This limitation is overcome by
printing a conductive layer of ink around
the edge of each side of the speaker film.
The material resembles thick sand-
wich wrap but has much more interesting
properties. Piezo film has an extremely
high output potential, about 10 times
greater than ceramic piezo materials.
Since the material is a thin, lightweight,
flexible film it can be glued onto shaped
designs. It also has a high mechanical
strength and good impact resistance.
Other attributes include:
• Wide frequency range. (0.001 Hz to
10 GHz).
• Low acoustic impedance (matching
water or human tissue).
• High dielectric strength.
• Good mechanical durability.
• Moisture resistance.
• It is resistant to many chemicals.
While speakers made from PVDF can
behave similarly to electrostatic speakers,
thin film piezo speakers do not need the
high voltages or complex electronics as-
sociated with electrostatic discharge to
produce sound. Any standard audio am-
plifier can be used with a small matching
transformer to create quality sound. This
means that PVDF material is perfect for
installing in tight spaces where audio is
needed. It can be formed and cut into
different shapes leaving its uses up to
the imagination.
Committed to developing this technol-
ogy is a team called Soundlazer, which
specialises in acoustic technology. The
company is seeking Kickstarter funding
of US$73 500 in order to develop the
specialised manufacturing processes
necessary to use this material in the
manufacture of low-cost high-quality
miniature speakers and headphones.
“We are determined to develop a
low cost kit, with the Soundlazer brand
name,” says Soundlazer ’s Richard
Haberkern. “We want this technology
in the hands of as many experimenters
and makers as possible. Our kit had to
include both the speaker film and the
electronics needed to produce good
quality sound. By working with manu-
facturers from around the world, I think
we have more than surpassed this goal.
Now the only thing needed is backing to
help produce these kits in large enough
quantities to make truly thin speakers a
reality,” he says. q
Sustainability Week
23 to 28 June, CSIR, Pretoria.
This year’s Sustainability Week is set to acceler-
ate the total number of sustainability projects,
under the theme ‘Get ready to put ideas in
motion.’ Thought leaders, policy makers, prac-
titioners and producers within the country and
beyond will share their knowledge. International
Convention Centre in Pretoria – undoubtedly a
highlight in the annual environmental calendar.
An exciting addition to the programme,
African Capital Cities Sustainability Forum,
hosted by the City of Tshwane, will seek to lay
the foundation for African cooperation at city
level and urban scale. In addition to the ex-
tended Green Building and Sustainable Energy
programmes, three new seminars on mining,
manufacturing and infrastructure have been
introduced.
Sustainability Week takes place at the CSIR
ICC from 23 to 28 June 2015.
Thin film piezo speaker material
Kickstarter specialist Richard Haberkerm demonstrates
PVDF, a thin plastic polymer sheet with converse piezo-
electric properties that make it ideal for use in audio
speakers.
When an electrical current from a sound source is
applied to opposing sides of the material, a converse
piezoelectric effect causes the PVDF film to distort and
vibrate.