Measurement of Surface Acoustic Wave on a Quartz Ball with Proximate Electrodes to Improve Performance of Ball Surface Acoustic Wave Device

Abstract

In order to improve the performance of ball surface acoustic wave (SAW) devices, we have developed an orientation control apparatus to find the Z axis of a quartz crystal ball by an optical birefringence measurement, and to find the X and Y axes by measuring the propagation characteristics of a SAW using an interdigital transducer (IDT), which is moved close to the ball using a translation stage. The soft spring of the vacuum chuck of the ball manipulator prevented damage to the ball or IDT during the contact. The concave shape of the ball holder of the chuck enabled repeatable alignment of the ball center and the manipulator axis. As a preliminary result, we confirmed that the SAW velocity variation had 60° periodicity and succeeded in identifying the -Y axis-equivalent direction on the quartz ball.

Fabrication of Thin Sensitive Film of Ball Surface Acoustic Wave Sensor by Off-Axis Spin-Coating Method

“…1) is suitable as a portable gas sensor; it realizes ultrahigh sensitivity not only by velocity (delay time) measurement but also by attenuation (amplitude) measurement when ultramultiple roundtrips (e.g., >100 turns) of the collimated SAW along the equator of the ball is achieved. [7][8][9][10][11][12][13][14] In fact, 0.001 vol % hydrogen gas was successfully detected from the amplitude change, 8) whereas the highest detectability of the planar SAW hydrogen sensor was only 0.1 %. 15) However, attenuation and scattering induced by the sensitive film coated on the roundtrip route must be low so as not to hinder the ultramultiple roundtrips, and thus the film must be thin (submicron thickness) and highly uniform.…”

Meandering collimated beam of surface acoustic waves on a trigonal crystal ball

“…We first describe the development of the orientationcontrol device by identifying the orientation of the ball using an orientation control apparatus ͑OCA͒, 16 and by fabricating an IDT at the +X axis and the -Y axis. The diameter of the device is 3.3 mm.…”

Development of High Precision Metal Micro-Electro-Mechanical-Systems Column for Portable Surface Acoustic Wave Gas Chromatograph

“…1. It consists of a ball SAW sensor to enhance the sensitivity by inducing multiple roundtrip of the SAW [2][3][4][5][6][7] and a micro separation column fabricated using micro-electro-mechanical-systems (MEMS) technology (MEMS column). 8,9) Although the downsizing of the capillary column using silicon MEMS technology has been studied for 30 years, 10,11) MEMS columns made of brittle materials such as silicon and glass do not have sufficient robustness for a portable GC.…”