9 research outputs found
Moving liquids with light: Photoelectrowetting on semiconductors
Liquid transport in microchip-based systems is important in many areas such
as Laboratory-on-a-chip, Microfluidics and Optofluidics. Actuation of liquids
in such systems is usually achieved using either mechanical displacement11 or
via energy conversion e.g. electrowetting which modifies wetting. However, at
the moment there is no clear way of actuating a liquid using light. Here, by
linking semiconductor physics and wetting phenomenon a brand new effect
"photoelectrowetting" is demonstrated for a droplet of conducting liquid
resting on an insulator-semiconductor stack. Optical generation of carriers in
the space-charge region of the underlying semiconductor alters the capacitance
of the insulator-semiconductor stack; the result of this is a modification of
the wetting contact angle of the droplet upon illumination. The effect is
demonstrated using commercial silicon wafers, both n- and p-type having a
doping range spanning four orders of magnitude (6\times1014-8\times1018 cm-3),
coated with a commercial fluoropolymer insulating film (Teflon\textregistered).
Impedance measurements confirm that the observations are semiconductor
space-charge related effects. The impact of the work could lead to new
silicon-based technologies in the above mentioned areas