Thermal bend actuator material selection
View Patent ↗A thermoelastic device comprising an expansive element is disclosed. The expansive element is formed from a material, which is preselected on the basis that it has one or more of the following properties: a resistivity between 0.1 μΩm and 10.0 μΩm; chemically inert in air; chemically inert in the chosen ink; and depositable by CVD, sputtering or other thin film deposition technique.
1. A method for selecting a material for a thermal bend actuator of a printhead nozzlel, the method including the steps of:
selecting the material from the group including silicides and carbides of titanium; borides, silicides, carbides and nitrides of tantalum, molybdenum, niobium, chromium, tungsten, vanadium, and zirconium; and
selecting the material on the basis of ε, wherein ε is a dimensionless constant for the material in accordance with the formula
ɛ
=
E
γ
2
T
ρ
C
wherein E is Young's module of the material; γ is the coefficient of thermal expansion; T is the maximum operating temperature, ρ is the density and C is the specific heat capacity.
2. The method of claim 1 , comprising the step of normalizing the dimensionless constant relative to that of silicon.
3. The method of claim 2 , wherein said normalizing step comprises the steps of calculating the value of constant ε for the material at the maximum operating temperature and dividing the value by the value of constant ε obtained for silicon at that same temperature.
4. The method of claim 1 , wherein the material is further selected on the basis of m ε , where
m
ɛ
=
ⅆ
ɛ
ⅆ
T
=
E
γ
2
ρ
C
[
N
/
m
2
1
/
°
C
.
2
kg
/
m
3
Nm
/
kg
°
C
.
]
5. The method of claim 1 , wherein the material is further selected on the basis that the material
a resistivity between 0.1 μΩm to 10.0 μm.