Bio-electromagnetics for Healthcare and Security Applications
Bio-electromagnetics examines the interaction between electromagnetic (EM) fields and biological organisms and tissues. On the one hand, this includes biologically-generated fields; on the other hand, this includes externally-generated fields, such as the Earth's geomagnetic field or the many fields generated by modern electronic devices.
The effect of biological tissues on the performance of wearable wireless devices is explored in the Body-Centric Wireless Communication and Networks research theme. This effect can be utilised for EM sensing of biological tissue properties. One example is the non-invasive monitoring of blood glucose levels (BGL). The electromagnetic properties of the body vary with BGL, which means the response of some resonator or EM device placed on the body will also vary, in theory, with the changes in BGL. Understanding this relationship is key to producing an EM sensor that can determine such physiological signals, which avoids the need for even minimally-invasive bio-sensor approaches. On the other hand, the use of ingestible or implantable wireless devices also requires an understanding of the interrelationship between the device and the surround tissue(s). Work in this area includes the development of digital and physical tissue phantoms (such as that in the header image above), the development and characterisation of microwave devices for wireless wearable physiological monitoring systems, and investigations to quantify the relationship between the various physiological parameters and the microwave response, including subject-specific variations.
The effect of biological tissues on electromagnetic waves can also be utilised for imaging purposes. The most well-known examples of this are X-ray imaging systems and the related X-ray Computed Tomography (CT) imaging systems. X-ray imaging finds application in healthcare (ranging from dentistry to imaging of the whole body), security (e.g., airport scanners) and industry (e.g., checking for structural integrity of pipes). However, X-rays are an ionising form of electromagnetic radiation, with associated health risks. Lower-energy non-ionising waves, such as at the THz, millimetre-wave and microwave frequency bands, can also be used for imaging, without the risks of X-rays.
Our studies in this domain include assessments of the effects of EM waves on the general public, EM biological anomalies detection methods, medical imaging schemes using EM waves, studies on the latest state-of-the-art medical treatments, and enhanced EM-assisted drug-delivery methods.
Our research aims to lead in innovation and in the development of more biologically-friendly, ecologically-sustainable and application-participator technologies and solutions.
Interaction with the Body (Compliance and SAR Assessments)
The Specific Absorption Rate (SAR) is used in dosimetry to denote the transfer of energy from the EM fields to biological materials (rate of energy deposition per unit mass of tissue).
Our studies involve the utilisation of experimental and numerical methods to investigate the effects of EM wave absorption within tissues due to exposure to RF sources. The SAR induced within the human body, especially the head and brain, are typically evaluated by computing the absorption strength and the location of peaks/maxima.
Understanding the underlying interaction mechanisms caused by RF exposure is necessary for assessing the possible impact on human health. The interaction of EM fields with biological systems can be categorised by several mechanisms, depending on the type and frequency of exposure.
Digital representation ("phantom") of a rat with (top) computed SAR distributions and (bottom) the computational method.
EM Absorption within the Body vs. Age
Our studies include investigations on the effects of ageing on the level of interaction with EM waves, and whether such changes may have different implications on the human or animal well-being. Ageing variations have included the impact of body size changes, changes to dielectric properties due to ageing and other factors.
Slices through the rat digital phantom showing the location of the different tissues, each with specific dielectric properties (false colour for clarity).
Macroscopic and Microscopic Electroporation Studies
As part of the Electromagnetics and Antenna activities, the group has focused on the interactions of electromagnetic waves with biological matter (specifically on the cellular, sub-cellular and molecular levels), both experimentally and numerically. Electroporation is a non-thermal scheme based on applying short but intense pulses to the biological cells or tissues. The conductivity and permeability of the cell membrane can be increased dramatically during the process, which allows the large-sized molecules to flow through in both directions.
Molecular dynamics presents a microscopic view of electroporation that conventional observations cannot. Although the method has some challenges, it can be used to reveal some fundamental behaviour at the atomic level that is later confirmed from the experiment. Therefore, we have a number of studies where we combine the molecular dynamics observations with the experimental results to deepen the understanding of the electroporation process.
In our studies, we use evidence-supported-theory to describe the process of cellular electroporation by the means of experimental applicators with state-of-the-art sources and measurement methods, complemented with numerical computations of the molecular interactions with the fields applied (using Molecular Dynamics computation tools).
Assessment of dielectric properties and body composition
The interaction of EM waves with matter is depend on a number of parameters, one of which is the dielectric properties of the exposed material. In our studies, we apply various techniques to (i) study the effects of the variation of these properties within the exposed body; and/or (ii) estimate the characteristics of the exposed material by applying the inverse process. The latter is rather important, not only to predict the composition of the body (e.g., fat layers, etc.), but also to detect potential abnormalities within the body, such as cancerous regions. The techniques applied many include any of the impedance measurements, EM imaging, or dedicated scanning or radar techniques.
Calibration of the Agilent Dielectric Probe using deionised water.
Nano-particle Applications in Medical Fields
Research into the applications of Nano-particles (NPs) has found increased interest in diagnostics, imaging, and therapeutics in biology and medicine. In particular, Gold nano-particles (GNPs) have received much attention, because of their distinctive optical, electronic, and molecular-recognition properties. In medical applications, we look into the potential applications of GNPs for better targeting of EM-generated hyperthermia treatments of cancer. In essence, the EM illumination of GNPs can result in energy absorption and selectively heat and abolish tumour regions without affecting healthy tissue. In other studies, we explore the potential of targeted NPs for non-invasive ablation and drug delivery in radiofrequency (RF) EM fields. These studies aim to reveal the mechanism of GNPs heating under exposure, to study the molecule-targeting procedure of NPs, and to optimise the delivery of GNPs directed via novel antenna systems.
Highlights and Research Outcomes
Selected Research Grants and Projects
- “Numerical dosimetry on the interactions of EM waves with brain tissues”, DSTL, 2004.
- “Assessments on the EM interactions with humans as a function of dielectric property variations with age”, MCL-UK 2006
- “Modelling RF interaction with biological body, tissues and cells” DSTL (2007)
- “RF detection of body fat” (Philips/EPSRC) 2008
- “Antenna technology for healthcare and imaging” (EPSRC) 2008
- “Macro- and Micro-scopic studies on the Electroporation of Cells: cellular, sub-cellular and molecular assessments”, 3Y-FT PhD studentship 2012.
- “Assessment of the interaction of EM signals from Smart-Meters on the general population” (Public Health England) 2014.
- “Wearable and implantable antennas for in- and on-body applications”, 3Y-FT PhD studentship, 2014.
- “Abdominal Fat Detection technique using EM waves”, 5Y-PT PhD studentship, 2014.
Selected Recent Publications
- Yilmaz T, Foster R and Hao Y (2014), "Broad-Band Tissue Mimicking Phantoms and a Patch Resonator for Evaluating Non-Invasive Monitoring of Blood Glucose Levels", IEEE Transactions on Antennas and Propagation, vol. xx, no. x, pp. xx-xx, DOI: 10.1109/TAP.2014.2313139
- Liu X, Chen H-J, Yang B et al. (2013), "Dielectric Property Measurement of Gold Nanoparticle Dispersions in the Millimeter Wave Range", Journal of Iinfrared Millimeter and Terahertz Waves, vol. 34, (2) 140-151.
- Liu X, Chen H-J, Alfadhl Y et al. (2013), "Conductivity and frequency dependent specific absorption rate", Journal of Applied Physics vol. 113, (7)
- Liu X, Chen HJ, Chen X et al. (2012), "Low frequency heating of gold nanoparticle dispersions for non-invasive thermal therapies", Nanoscale vol. 4, (13) 3945-3953.