Towards a wireless microsystem for liquid analysis

The paper describes both semi-wireless and wireless (433 MHz) liquid sensing systems based upon dual shear horizontal surface acoustic wave (SH-SAW) devices and introduces a novel design concept and a novel principle of detection. Each system comprises an uncoated passive SH-SAW device, a liquid microcell, a device antenna and an associated signal processing unit. The LiTaO/sub 3/-based SH-SAW sensors have dual delay line configurations with different path lengths, the principle of detection being the attenuation and time delay between the signals. The sensors have no biochemical selective layer making them non-specific but create a robust/durable and low-cost system. This sensing system may be applied in the food/beverage industry, medical applications; a functionalized coating can be added for more specific biological applications.