PST Sensors Makes Major Strides in Printed Silicon
By David Savastano, Editor
One of the key value propositions of printed electronics is the ability to use printing processes to manufacture semiconductors. There have been some successes in this field, but mass commercialization has yet to emerge.
PST Sensors is poised to make a major breakthrough in this field. Led by directors Margit Harting and David Britton, who have been working on this technology as professors at the University of Cape Town (UCT), PST Sensors has developed and proven its technology to print silicon semiconductors at room temperature on any material, including paper, using conventional printing methods.
PST Sensors has developed environmentally friendly, non-toxic and ROHS compliant ink formulations which have either a water base or natural oil base, and is also working on silicon inks using environmentally friendly, naturally derived polymers and solvents. They have printed their silicon inks on paper, fabrics and plastic film, using screenprinting and other printing techniques.
Mr. Britton said that he and Ms. Harting have been working on the idea for more than a decade at UCT. They found they could print their semiconductors, which opened up all sorts of possibilities, and they chose photovoltaics (PV) as the initial target for their technology. However, PV did not prove to be ideal, and Mr. Britton and Ms. Harting went back to the drawing board, and hit upon the idea of printed silicon
“Despite early successes with the PV, by the end of 2008 it was obvious to us that we had hit a ceiling with the technology, and it would need further R&D,” Mr. Britton said. “PV wasn’t market ready, and transistor logic would also need further development and had serious competition from thin-film Si and microelectronics. Fully passive electronics would just make us one of thousands of thick-film companies, and supplying inks and pigments alone would put us at the bottom of the food chain.
Margit Harting, right, and team members, from left, Ulrich Mannl, Batsirai Magunje and Stanley Walton, showcase PST Sensors’ freshly printed Tiger thermometer.
“This left us with one area where printed silicon is clearly better than the competition and can offer new features (large area, conformability, flexibility, etc.) required by the market,” Mr. Britton added. “In 2008, the temperature sensor market was already a billion dollar market - much larger than printed electronics.”
In 2010, the groundwork for PST Sensors was put in place. Ms. Harting and Mr. Britton negotiated the formation of the company and the assignment of the IP from UCT to PST. The sensor technology was independently validated by Soligie, which has printed demonstration thermistors using PST inks. By Nov. 5, 2010, PST Sensors was formally registered as a limited company in South Africa.
Temperature sensors have proved to be a strong initial market for PST.
“Although we have a complete printed silicon electronics technology, the most important area for us in the near future is going to be sensors, specifically temperature sensors,” Mr. Britton said. “After time, temperature is the most measured quantity in applications in all sectors: health and leisure; automotive and aerospace; transport and logistics; food and consumer goods; white goods and consumer electronics; marketing and advertising.
“Conventional temperature sensors are widely used in all of these sectors, but often have distinct disadvantages resulting from their size, shape and packaging, as well as production cost,” Mr. Britton added.
Since forming the company, PST Sensors has received a lot of interest. Mr. Britton said that an announcement is expected shortly regarding joint development of applications with a major player in the field. Mr. Britton added that PST is concentrating on developing its sensor technology, the latest being the thermal imaging mat, which is an array of individual sensors, with an eye on designing fully flexible sensors.
“The current generation of sensors are only conformable, not flexible,” Mr. Britton said. “We have design prototypes of fully flexible sensors, which will also be released next year.”