i-Rheo drop
Supervisor: Dr Akhil Kallepalli and Dr Manlio Tassieri
School: Physics and Astronomy
Description:
The aim of this project is to develop a new analytical & experimental method for measuring the viscoelastic properties of complex (biological) fluids by using only a few microliters of sample volume, i.e., a droplet.
The linear viscoelastic (LVE) properties of materials have been successfully correlated [1], to their topological structure, from a macroscopic length scale at relatively low frequencies, down to an atomic length scale for frequencies of the order of THz. Thus, the importance of having the widest possible range of frequencies to gain a full picture of the materials’ structure. Conventionally, the materials’ LVE properties are measured by means of cumbersome machines (i.e., rheometers) that apply a simple oscillatory shear stress and measure the deformation of the material (i.e., strain). Despite their effectiveness, these are time-consuming measurements that are limited in the number of explored frequencies and require millilitres of sample volume, which is often inappropriate for biological samples. Hence, minimising the sample volume to a single drop (< 50 microlitres) is important.
The novel technique is underpinned by the analytical method developed by Dr Tassieri [2,3] for determining the viscoelastic properties of complex fluids over the widest range of experimentallyaccessible frequencies, via the Fourier transform of time-depended measurables encoding the fluids’ mechanical properties. In this case, the measurement of the relaxation process of an induced deformation (i.e., strain) of a single droplet subject to a constant gravitational force (i.e., stress) will be performed in the time-domain and monitored by means of a high-speed camera, while the outputs will be obtained in the frequency-domain. The proposed method will be validated using fluids of known viscoelasticity, then applied to biological samples, such as saliva and tears.
Once corroborated, the novel experimental procedure will underpin the development of a small (<shoe box) low-cost 3D printed mobile device, which will be based on Arduino technologies and will not require external accessories, such as pumps to generate fluid flow. The devices will represent a catalyst for both multidisciplinary studies of viscoelastic biological fluids and instrument manufacturing companies (e.g. point-of-care devices).
[1] J.D. Ferry, Viscoelastic Properties of Polymers, 3rd Ed., Wiley, New York, 1980.
[2] M. Tassieri et al., New J. of Physics, 14, 115032 (2012).
[3] M. Tassieri et al., Journal of Rheology 60, 649 (2016).