In situ TEM Observation and Energy Harvesting using MEMS Actuators and Sensors
Hiroyuki Fujita
CIRMM and LIMMS, Institute of Industrial Science
The University of Tokyo
A new experimental setup has been established to visualize the dynamics of nano
junctions between two sharp tips under tensile or shear force. In the setup, a MEMS
device was inserted in the transmission electron microscope (TEM). By driving MEMS
actuators, we brought tips into contact and formed a junction. The tensile and shear
testing of the junction was conducted, while its deformation was in situ observed by
TEM. Furthermore, the heat transfer through a short and thin Si junction was measured
using an integrated heater and a temperature sensor. We observed larger heat transfer
than the bulk because of ballistic heat transfer.
Also we have developed novel fabrication technology to form electrets in MEMS
structures. During thermal oxidation of silicon, positive ions are introduced in the SiO2
film. The ions are activated by applying DC voltage at elevated temperature. The
residual voltage is around 200-300 over gaps of a few micrometers. The strong electric
field created by the electret allowed us to produce large force with small driving
voltages or to generate electric power from environmental vibration which is captured
by a proof mass attached with the moving electrode. Based on the latter effect, we have
been developing MEMS-based energy harvesters for micro wireless sensor nodes.