SEM picture of fabricated piezo-thermal probe. Inset: Probe tip (<1 μm).
The vertical axis is the change of the resistance of the deflection sensing element measured with a multimeter, whereas the horizontal axis is the Z-axis movement toward and away from the probe. The blue thick line represents the trace (i.e., the glass substrate moving toward the probe) and the red thin line represents the re-trace (i.e., glass substrate moving away from the probe).
A near linear relationship of power with temperature is observed. A variable power supply (Keithley 2400) was used to increase the power through the heating element while monitoring the temperature with an external thermocouple brought in contact with the tip.
The melting temperature of naphthalene was measured with the piezo-thermal probe. Figure 4(a) shows the change in resistance of the deflection sensing element on the vertical axis with temperature increase of the heating element on the horizontal axis. As expected the increase in temperature caused by incremental increase in power through the heating element also increases the resistance of the deflection sensing element. Figure 4(b) shows the first order derivative (dRpiezo/dT) of the deflection sensing element on the vertical axis with temperature increase of the heating element on the horizontal axis. Near the reported melting temperature a local decrease in resistance is observed in both Figs. 4(a) and 4(b) at 78.5 °C indicating a glass transition.
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