A paper on laser vibrometer characterization of the ultrasonic coupling into the microfluidic chips used in the NPL/UCL microbubble trapping project as presented at the 12th Anglo-French Physical Acoustics Conference (AFPAC2013) 16-18 Jan 2013, has been published as C. Fury et al, Laser vibrometry characterisation of a microfluidic lab-on-a-chip device: a preliminary investigation J Phys: Conf Ser 498 012002 (2014).
From the abstract: Since their original inception as ultrasound contrast agents, potential
applications of microbubbles have evolved to encompass molecular imaging
and targeted drug delivery. As these areas develop, so does the need to
understand the mechanisms behind the interaction of microbubbles both
with biological tissue and with other microbubbles. There is therefore a
metrological requirement to develop a controlled environment in which
to study these processes. Presented here is the design and
characterisation of such a system, which consists of a microfluidic
chip, specifically developed for manipulating microbubbles using both
optical and acoustic trapping. A laser vibrometer is used to observe the
coupling of acoustic energy into the chip from a piezoelectric
transducer bonded to the surface. Measurement of the velocity of surface
waves on the chip is investigated as a potential method for inferring
the nature of the acoustic fields excited within the liquid medium of
the device. Comparison of measured surface wavelengths with wave types
suggests the observation of anti-symmetric Lamb or Love-Kirchhoff waves.
Further visual confirmation of the acoustic fields through bubble
aggregation highlights differences between the model and experimental
results in predicting the position of acoustic pressure nodes in
relation to excitation frequency.