Microwave Selective Heating Enhancement for

Cancer Hyperthermia Therapy based on

Lithographically Defined Micro/Nano-particles

Yifei Wang, John Stang, Eugene Chung, Mahta Moghaddam, and Wei Wu*

Department of Electrical Engineering - Electrophysics

University of Southern California

Surgical Resection

Background

Moderate heating, hyperthermia, in the

range of 42 to 47°C, can destroy the

tumor while leaving the normal tissue

unaffected.

Noninvasive & nontoxic

Treating deep embedded tumors

Fails to remove all of the cancerous cells

Tumors inoperable because of the position

or the conditions of the patients

Side effectsRadio/Chemotherapy

Background

Infrared LightSynthesized

ParticleGood selectivity, but penetration depth

in the order of one millimeter.

MicrowaveSynthesized

ParticleGood penetration, but morphologies

and sizes limited by chemical synthesis.

Current selective hyperthermia approaches

1. D. P. O’Neal, L. R. Hirsch, N. J. Halas, J. D. Payne, J. L. West, Cancer Letters 2004, 209, 171.

2. R. Hergt, R. Hiergeist, M. Zeisberger, G. Glöckl, W. Weitschies, L. Ramirez, I. Hilger, W. Kaiser, J. Magn.

Magn. Mater. 2004, 280, 358.

Background

Our goal of this project is to use lithographically defined

micro/nano-particles to overcome the limitations of chemical

synthesis. (Wang, Y., Wu, W., et al (2016), Advanced Materials Technolo. doi:

10.1002/admt.201600038)

Heating source: external microwave irradiation (enough penetration depth)

Particle requirements:

high microwave absorption efficiency

smaller than Red Blood Cell (8 μm)

Extreme sub-wavelength particles

Magnetic dipoles

Electric dipolesWang, Y., Wu, W., et al (2016), Advanced Materials Technolo. doi:

10.1002/admt.201600038

Numerical Studies

Comparison between magnetic dipoles and electric dipoles

Excited by a 1.9 GHz harmonic plane

wave with electric field of 1V/m

Gold is selected.

Larger is better, for both magnetic

dipoles and electric dipoles.

8 μm limitation

Numerical Studies

Comparison between magnetic dipoles and electric dipoles

Magnetic dipoles: not change much

Electric dipoles: a phase boundary of

parameter a.

Aspect ratio of the electric dipole

should be at least 130:1.

Disk-shaped magnetic dipoles are

desired.

Numerical Studies

A nickel core is put inside the

gold disk, to increase the

central magnetic flux density.

The simple gold disk structure

is still preferred, because of

the much simpler fabrication

process and almost the same

absorption efficiency.

Fabrication Process

The fabrication and releasing

process of lithographically defined

particles (LDPs).

Lift-off process

LOL 2000 as sacrificial layer

Parylene film to protect the

LOL 2000 and to support the

gold disks

Particle Collection

LOL stripper

Centrifugation

Adding DI water

Easy to combine or divide the LDPs quantity

Centrifugation has no harm to particles.

Particle-suspended hydrogel setup

Particle Collection

Particle-suspended hydrogel setup

Adding the prepared

LDP/water solution

Mixed by ultrasound

vibration Stable

Viscous

Heating Characterization

One 3-in wafer, 3×107 LDPs

Higher concentration, larger

heating enhancement.

Two steps heating, especially

for high concentration.

Potential for localized

hyperthermia treatments.

Summary

We presents a novel approach to utilize lithographically defined

micro/nano-particles as microwave absorbers to achieve selectively

localized heating under microwave radiation for cancer hyperthermia

therapy.

The structures and materials were optimized by numerical studies

using finite element methods.

Disk-shaped gold magnetic dipoles with induced eddy current were

selected as the particles.

The LDPs fabrication and collection processes were developed.

The microwave heating enhancement effects have been successfully

demonstrated by our particle-suspended hydrogel setup.

Acknowledgements

This project was supported in part by Ming Hsieh Institute (MHI) for

Engineering Medicine for Cancer, University of Southern California. We

also thank Prof. Pin Wang at the University of Southern California for

help with centrifugation.

Thank you for attention!

Q & A

Email: wu.w@usc.edu

Group website: http://www.usc.edu/dept/ee/wugroup/