Inductively coupled RF telemetry is an optimal method for both power supply and data transmission in long
term artificial implants due to small size, high reliability, and extended life span of the device. In this research,
we propose the use of the same technique for secure remote interrogation and powering of a human implantable,
Surface Acoustic Wave (SAW) correlation based, passive microvalve. This is carried out by interrogating the
microvalve with a Barker sequence encoded BPSK signal. In this paper we present the development of a FEM
model for the derivation of the induced voltage on a miniature (2.5×2.5×1 mm), inductively coupled, biocompatible
spiral antenna/coil, interrogated by a 7.5×7.5×0.2 cm spiral antenna/coil in the near field. The
amount of power transferred at a 30-160 MHz range was derived using the S21 coupling response when the two
antennas are separated by a human body simulant of 5 cm depth. Furthermore, the effect of varying magnetic
coupling on the induced voltage, due to the misorientation of coils/antennas is analysed.
Complex signal processing functions can be performed by acoustic wave correlators, with simple structures,
through the variation of electrode patterns. Numerical simulations of Surface Acoustic Wave (SAW) correlators,
previously limited to analytical techniques like delta function and equivalent circuit models, require simplification
of second order effects such as backscattering, charge distribution, diffraction, and mechanical loading. With
the continual improvement in computing capacity, the adaptation of finite element modelling (FEM) is more
eficient for full scale simulation of electromechanical phenomena without model oversimplification. This is
achieved by resolving the complete set of partial differential equations. In this paper a novel way of modelling
a 3-dimensional acoustic wave correlator using finite element analysis is presented. This modelling approach
allows the consideration of different code implementation and device structures. This is demonstrated through
the simulation results for a Barker sequence encoded acoustic wave correlator. The device response for various
surface, bulk, and leaky modes, determined by the excitation frequency, are presented. Moreover, the ways in
which the gain of the correlator can be optimised though variation of design parameters is also outlined.
Numerical simulations of SAW correlators so far are limited to delta function and equivalent circuit models. These
models are not accurate as they do not replicate the actual behaviour of the device. Manufacturing a correlator
to specifically realise a different configuration is both expensive and time consuming. With the continuous
improvement in computing capacity, switching to finite element modelling would be more appropriate. In this
paper a novel way of modelling a SAW correlator using finite element analysis is presented. This modelling
approach allows the consideration of different code implementation and device structures. This is demonstrated
through simulation results for a 5×2-bit Barker sequence encoded SAW correlator. These results show the effect
of both bulk and leaky modes on the device performance at various operating frequencies. Moreover, the ways
in which the gain of the correlator can be optimised though variation of design parameters will also be outlined.
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.
In this paper we propose the use of a RF controlled microvalve for implementation on a PZT substrate for biomedical
applications. Such device has a huge range of applications such as parallel mixing of photo-lithographically defined
nanolitre volumes, flow control in pneumatically driven microfluidic systems and lab-on-chip applications. The
microvalve makes use of direct actuation mechanisms at the microscale level to allow its use in vivo applications. A
number of acoustic propagation modes are investigated and their suitability for biomedical applications, in terms of the
required displacement, device size and operation frequency. A theoretical model of the Surface Acoustic Wave (SAW)
device is presented and its use in micro-valve application was evaluated using ANSYS tools. Furthermore, the wireless
aspect of the device is considered through combining the RF antenna with the microvalve simulation by assuming a high
carrier frequency with a small peak-to-peak signal. A new microvalve structure which uses a parallel type piezoelectric
bimorph actuator was designed and simulated using ANSYS tools. Then, further optimization of the device was carried
out to achieve a better coupling between electrical signal and mechanical actuation within the SAW device.
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