This article presents a novel piezoelectric fluid ejector that is base
d on a variation of the design of a flextensional transducer that exci
tes axisymmetric resonant modes in a clamped circular membrane. The tr
ansducer is made by bonding a thin piezoelectric ring to a thin, fully
supported, circular membrane. The transducer design is optimized for
maximum flexure at the lowest order resonant frequency using finite el
ement modeling. The fluid ejector is formed by placing a fluid, at atm
ospheric pressure, behind one face of the membrane and an orifice in i
ts center. We achieve continuous or drop-on-demand ejection of the flu
id by applying the appropriate voltage to the piezoelectric transducer
. We present results of ejection of water, ink, powder, and photoresis
t. The application of photoresist with minimum waste on silicon wafers
is one of the motivations for developing this device. In present appl
ications, over 95% of the photoresist is wasted and has to be disposed
as a toxic material, thus making this one of the more expensive steps
in integrated circuit manufacturing. The ejector is harmless to sensi
tive fluids and can also be used to eject fuels, chemical and biologic
al samples. The ejector configuration is unique in that it can be impl
emented using silicon micromachining as a microelectromechanical syste
m, thus allowing the manufacture of true two-dimensional arrays of eje
ctors. (C) 1997 American Institute of Physics.