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What is the current status of research on mm-Wave frequencies

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1 What is the current status of research on mm-Wave frequencies
What is the current status of research on mm-Wave frequencies? - in relation to health Andrew W Wood School of Health Sciences Swinburne University of Technology Melbourne, Australia

2 5G and Millimetre waves Designation Frequency range Wavelength range L band 1 to 2 GHz 15 cm to 30 cm S band 2 to 4 GHz 7.5 cm to 15 cm C band 4 to 8 GHz 3.75 cm to 7.5 cm X band 8 to 12 GHz 25 mm to 37.5 mm Ku band 12 to 18 GHz 16.7 mm to 25 mm K band 18 to 26.5 GHz 11.3 mm to 16.7 mm Ka band 26.5 to 40 GHz 5.0 mm to 11.3 mm Q band 33 to 50 GHz 6.0 mm to 9.0 mm U band 40 to 60 GHz 5.0 mm to 7.5 mm V band 50 to 75 GHz 4.0 mm to 6.0 mm W band 75 to 110 GHz 2.7 mm to 4.0 mm F band 90 to 140 GHz 2.1 mm to 3.3 mm D band 110 to 170 GHz 1.8 mm to 2.7 mm Current 5G deployment ? Future N.B. mm waves have been around for a while (~1900: JC Bose), but only now being exploited in consumer technologies.

3 mm wave absorption by air
Strong absorption due to water and O2 Source: Wikipedia

4 Absorption by pure water
mm-waves = 103 mm Source: Wozniak & Dera, 2007, Springer

5 Mm wave research: Herbert Fröhlich
1905 – 1991, University of Liverpool Fellow of Royal Society Proposed theory of coherent excitations in biological systems – region of 100 GHz, corresponding to mm waves Several books, but Fröhlich & Kremer (1983) reports several experimental group’s findings Some papers in Nature

6 Early key references Webb & Dodds (1968). Inhibition of bacterial cell growth by 136 GHz microwave. Nature 218: Grundler, Keilmann& Frohlich (1977). Resonant growth rate response of yeast cells irradiated by weak microwaves. Physics Letters A 62: GHz Furia, Hill & Gandhi (1986). Effect of millimetre wave irradiation of growth of saccharomyces cerevisiae. IEEE Trans BME: 33: three frequency ranges between and GHz– No Effect

7 Work of Marvin Ziskin, MD
From initial work in obstetric ultrasound, went on to investigate mm-wave effects, particularly in skin: use in therapy Recipient of BEMS d’Arsonval award in 2011 Key reference: Bioelectromagnetics 34:3-14 (2013) Collaborators: M Zhadobov, S Alekseev, R Saulau, Y Le Drean Mechanism: stimulation of a) nervous b) immune system

8 GHz tissue absorption Above 10 GHz, tissue is strongly absorbent (Data from Gabriel)

9 Ziskin’s work on skin models
Skin thickness range 0.1 – 1.5 mm Epidermis ~ 0.1 mm Note sweat glands and hair follicles Nerve endings are just below epidermis Blood capillaries are also present in dermis

10 Skin models Multilayered models (for mm-wave frequencies)
Alekseev & Ziskin Bioelectromagnetics 28:331–339, 2007 Concluded: Model 1 OK for forearm, but 3 better; for palm skin, need 2 or more layers

11 Structure of cornea Thickness 0.5 – 0.8 mm Densely innervated
No blood vessels Susceptible to ‘flash burn’ (welder’s flash) usually due to UV but also IR

12 US military and use of mm waves
Lots of papers & reports on military radar safety standards, from 1950s Pakhomov et al. Lit. review. BEMS 19:393 (1998) – including extensive work in former USSR, esp. use in therapy Work on ‘less than-lethal’ weapons. The Silent Guardian (95 GHz focussed beam, inflicting intense pain at distances of tens of metres) Airport security scanning

13 Yuri Feldman – helical sweat glands
Phys Med Biol 54:3341 (2009) Modelling (incorporating helices) and measurement from palm of hand Modelling predicts 97 GHz Other modelling predicts ~ 400 GHz

14 Biological changes? Use for therapy: high success rates reported. Thermal? No effects on gene expression: Ziskin & Zhadobov groups Cellular proliferation: reduction of cancer metastasis reported in at least 3 studies Effects on membranes: shape modification above 9 W/m2 Immune & inflammatory systems: increased rates of healing (as low as 1 W/m2) Protein denaturation is chief thermal concern See Wu, Rappaport & Collins (2015) doi: /MMM

15 Swinburne projects Prediction & measurement of dielectric parameters for water & biological materials in range 1 GHz – 100 THz. Dielectric parameters of relevant biomaterials in this range. Model of skin, including glands, hair follicles, rete ridges and moles. Ear canal model SAR in RF workers in extreme conditions (including sweating and blood flow changes): effects of protective clothing Public exposure to wireless technologies (using MVG EME SPY200 system) Therapeutic tissue ablation modelling

16 Summary Skin and eyes are regions of concern in regard to 5G frequencies (6 – 60 GHz) and beyond Early concerns around proliferation of yeasts and bacterial spores unsubstantiated Ziskin work raises possibility of non-thermal mechanisms, but heat most likely explanation (for therapy outcomes) Could be resonant enhancement absorption due to skin structures What we know in relation to standards: basic restrictions based on thermal mechs. OK, but absorption patterns still need to be determined. N.B. metric is PD, not SAR

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