(a), Bending setup
for RF measurements. (b), A bent device array on a bending fixture.
(c), Calculated
mobility values from measured transconductance as a function of bending induced
strain
for both unstrained and strained devices.
(d), fT and fmax
of both unstrained and strained devices as a function of bending induced
external strain.
(October 30, 2015) Inspired
by mammals' eyes, University of Wisconsin-Madison electrical engineers have
created the fastest, most responsive flexible silicon phototransistor ever
made.
The innovative phototransistor could improve the performance
of myriad products - ranging from digital cameras, night-vision goggles and
smoke detectors to surveillance systems and satellites - that rely on
electronic light sensors. Integrated into a digital camera lens, for example,
it could reduce bulkiness and boost both the acquisition speed and quality of
video or still photos.
Developed by UW-Madison collaborators Zhenqiang
"Jack" Ma, professor of electrical and computer engineering, and
research scientist Jung-Hun Seo, the high-performance phototransistor far and
away exceeds all previous flexible phototransistor parameters, including
sensitivity and response time.
The researchers published details of their advance this week
in the journal Advanced Optical Materials.
Like human eyes, phototransistors essentially sense and
collect light, then convert that light into an electrical charge proportional
to its intensity and wavelength. In the case of our eyes, the electrical
impulses transmit the image to the brain. In a digital camera, that electrical
charge becomes the long string of 1s and 0s that create the digital image.
While many phototransistors are fabricated on rigid
surfaces, and therefore are flat, Ma and Seo's are flexible, meaning they more
easily mimic the behavior of mammalian eyes.