Mechanical Technology March 2015

⎪ Nota bene ⎪

Thin film piezo speaker material

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 Fundamentals to Energy Management Training 4-6 May, Johannesburg Thieda Ferreira, Energy Training Foundation +27 41 582 2043 info@entf.co.za thieda@entf.co.za www.entf.co.za April 2015 4 th Annual Concentrated Solar Thermal Power Conference & Exhibition CSP Today South Africa 2015 14-15 April, Cape Town Brandon Páramo brandon@csptoday.com May 2015 SME Pressure Vessels Section VIII Division 1 (3 Day) 4-6 May Johannesburg, Cedar Park Hotel Phindi Mbedzi:+27 11 325 0686 phindi@2kg.co.za www.2kg.co.za 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 Industry diary

P olyvinylidene 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

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.

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. www.sustainabilityweek.co.za

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Mechanical Technology — March 2015