Improving the security and actuation of wireless controlled microvalve

Abstract

A wireless microvalve would have a wide range of applications, including biomedical applications such as fertility control and nano-litre drug delivery. Arguably the most important aspect for such a device is a secure method to actuate the valve, such that it is not actuated through the spectrum of electromagnetic radiation already present in the surrounding environment. Additionally, many of the possible applications are sensitive to electromagnetic (EM) radiation so the device should be designed to only require the minimum amount of EM input to actuate the valve. To overcome this problem, we propose the use of a coded interdigital transducer (IDT) to respond only to a coded signal. For the wireless microvalve to be useful in biomedical applications, the IDT's response to a specifically coded RF signal must be much greater than its response to another coded RF signal, even if the two codes are very similar, i.e. improve the signal ratio of the device. In this research we demonstrate a number of code sequences that have a correlation function such that the peak response is unique and can be used to provide a high signal-to-noise ratio (SNR) surface acoustic wave. That results in a unique activation of the device when the interrogating RF signal code sequence matches the stored code sequence in the device. Also we will investigate the trade-off between the needed code length to ensure secure operation and the area constrain of the device within the context of biomedical application. For this purpose, the IDT is modelled as a pulse compression filter, which correlates the input signal with a stored replica.