Colloid Vibration Potential Imaging - An initiation and preliminary results

Particles in electrolyte media usually carry electrical charges. When externally excited, charged particles vibrate and generate a secondary electric field that produces the so-called Colloid Vibration Potential (CVP). Hitherto, CVP due to different source of excitation has been called, treated and utilised differently and separately. For example, when an ultrasound pulse travels through a colloidal medium, the ultrasound vibration potential (UVP) can be detected from outside the medium, which reports specific features of the colloid along the path of the ultrasound. The phase difference and relaxation frequency of the synthetic electric field from an electrical excitation and electrical vibration potential (EVP) can also be related to specific features of colloids.

Our vision is to develop new imaging techniques based on UVP, EVP and their combination. We call this CVP imaging. It is able to reveal physiochemical features of colloids that other conventional structural imaging techniques are unable to ‘see’.

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Figure 1: Charged particles and their responses to different sources of excitation: (a) a charged particle and the electrical double layer structure; (b) a pulsed ultrasound wave propagation and measurements in relation to the pulse’s position in the time domain; (c) a continuous electrical wave and measurements in relation to the internal conductivity distribution in the frequency domain [1]
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Figure 2: One-dimensional imaging of a three-layer “sandwich” with a mesh sensor beneath the bottom surface of the “sandwich”. Sample: The agar layer sandwiched by two silica suspension layers (8 nm, 5wt%); Left: an illustration for the “sandwich” set-up; Right: signals from the ultrasound pulses travel through the “sandwich” (0.21 mV (pk-pk) obtained from the right pulses) [2, 3]

 

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Figure 3: (a) Relaxation frequency vs. particle size in 5.0 wt% silica suspensions; (b) Left: Measured electric impedance spectra (imaginary part vs. frequency) for L-glutamic acid solution at 49.5 °C, 40.5°C, 32.7°C, and 25.5 °C；Right: photographs of different crystal shapes.EIT has been recognised as a potential tool for monitoring and controlling of crystallization in pharmaceutical industry by the measurement of essential process descriptors [4, 5, 6].

Author Information: Mi Wang, Institute of Particle Science and Engineering, School of Process, Environmental and Materials Engineering, Email: m.wang@leeds.ac.uk

References:
1. Wang, M. (2009) “Arts of Inner Vision”, Inaugural Lecture, University of Leeds, http://www.engineering.leeds.ac.uk/InauguralLecture.shtml
2. Guan, P., Wang, M., Schlaberg, H.I. and Khan, J.I. (2010) “Towards A-Scan Imaging via Ultrasonic Vibration Potential Measurements”, Nuclear Engineering Design J., in press
3. Schlaberg, H.I., Wang, M., Guan, P. and Khan, I.J. (2010) “Ultrasound Vibration Potential measurement techniques for imaging”, Nuclear Engineering Design J., in press
4. Zhao, Y., Wang, M. and Hammond, R.B. (2010) “Characterisation of Crystallisation Processes with Electrical Impedance Spectroscopy”, Nuclear Engineering Design J., in press
5. Zhao, Y., Wang, M. and Hammond, R.B. (2010) “Electrical Impedance Spectroscopy Study on Colloidal Suspensions for Particle Size Determination”, in Proceedings of PITTCON-2010, Orlando,
6. Zhao, Y., Wang, M. and Hammond R.B. (2009) “Electrical Impedance Spectroscopy Study on Charged Particles in Crystallisation Processes”, in Proceedings of PITTCON-2009, Chicago, 1300-13P