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  • Compact Helical Antenna for Smart

    Implant Applications

    DISSERTATION

    von der Fakultt fr Elektrotechnik und Informationstechnik

    der Technischen Universitt Chemnitz

    zur Erlangung des akademischen Grades

    Doktor der Ingenieurwissenschaften

    (Dr. Ing.)

    Vorgelegt

    von: M. Sc. Dmitriy D. Karnaushenko

    Geboren am: 04. Mrz 1986 in Novokuznetsk

    Eingereicht am: 22.05.2017

    Gutachter: Prof. Dr. Oliver G. Schmidt

    Prof. Dr. Frank Ellinger

    Tag der Verleihung: 19.10.2017

    DEUTCHLAND 2017

    Online link: http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-230942

  • ii

  • iii

    Abstract

    Medical devices have made a big step forward in the past decades. One of the most noticeable medical

    events of the twenties century was the development of long-lasting, wireless electronic implants such

    as identification tags, pacemakers and neuronal stimulators. These devices were only made possible

    after the development of small scale radio frequency electronics. Small radio electronic circuits

    provided a way to operate in both transmission and reception mode allowing an implant to

    communicate with an external world from inside a living organism. Bidirectional communication is

    a vital feature that has been increasingly implemented in similar systems to continuously record

    biological parameters, to remotely configure the implant, or to wirelessly stimulate internal organs.

    Further miniaturisation of implantable devices to make the operation of the device more comfortable

    for the patient requires rethinking of the whole radio system concept making it both power efficient

    and of high performance. Nowadays, high data throughput, large bandwidth, and long term operation

    requires new radio systems to operate at UHF (ultra-high frequency) bands as this is the most

    suitable for implantable applications. For instance, the MICS (Medical Implant Communication

    System) band was introduced for the communication with implantable devices. However, this band

    could only enable communication at low data rates. This was acceptable for the transmission of

    telemetry data such as heart beat rate, respiratory and temperature with sub Mbps rates. Novel

    developments such as neuronal and prosthetic implants require significantly higher data rates more

    than 10 Mbps that can be achieved with large bandwidth communicating systems operating at higher

    frequencies in a GHz range. Higher operating frequency would also resolve a strong issue of MICS

    devices, namely the scale of implants defined by dimensions of antennas used at this band. Operation

    at 2.4 GHz ISM band was recognized to be the most adequate as it has a moderate absorption in the

    human body providing a compromise between an antenna/implant scale and a total power efficiency

    of the communicating system.

    This thesis addresses a key challenge of implantable radio communicating systems namely an

    efficient and small scale antenna design which allows a high yield fabrication in a microelectronic

    fashion. It was demonstrated that a helical antenna design allows the designer to precisely tune the

    operating frequency, input impedance, and bandwidth by changing the geometry of a self-assembled

    3D structure defined by an initial 2D planar layout. Novel stimuli responsive materials were

    synthesized, and the rolled-up technology was explored for fabrication of 5.5-mm-long helical

    antenna arrays operating in ISM bands at 5.8 and 2.4GHz. Characterization and various applications

    of the fabricated antennas are successfully demonstrated in the thesis.

    __________________________________________________________________________________________________________________

    Keywords: Helical antenna, rolled-up polymeric tubes, strain-engineering, injectable antenna,

    specific absorption ratio, S-parameters, self-assembly, polymeric platform, bridging element,

    finite element methods.

    Dmitriy D. Karnaushenko

    Compact helical antenna for smart implant applications

    135 Pages, 52 Figures, 3 Tables, 395 References

  • iv

  • Table of content

    v

    Table of Contents

    Abstract iii

    List of acronyms 1

    1 Introduction 3

    1.1 Motivation ...................................................................................................................................................................... 6

    1.2 Objectives ....................................................................................................................................................................... 9

    1.3 The thesis structure................................................................................................................................................. 10

    2 Background 11

    2.1 Wireless medical implantable devices ............................................................................................................ 11

    2.1.1 Telemetry and drug delivery................................................................................................................................... 13

    2.1.2 Bioelectrical interfaces .............................................................................................................................................. 15

    2.2 Implantable wireless communication systems ............................................................................................ 18

    2.2.1 Types of communicating systems ......................................................................................................................... 18

    2.2.2 Electromagnetic radiation in a biological environment ........................................................................... 20

    2.2.3 Designs of implantable antennas ......................................................................................................................... 24

    2.3 Rolled-up self-assembling technology ............................................................................................................. 29

    3 Fabrication and characterization methods 33

    3.1 Thin film technology ............................................................................................................................................... 33

    3.1.1 Photolithography ......................................................................................................................................................... 33

    3.1.2 E-beam deposition ....................................................................................................................................................... 35

    3.1.3 Sputter deposition ....................................................................................................................................................... 37

    3.1.4 Chemical deposition .................................................................................................................................................... 38

    3.2 Characterization methods .................................................................................................................................... 40

    3.2.1 Profilometry.................................................................................................................................................................... 40

    3.2.2 Vector network analyzer .......................................................................................................................................... 41

    3.2.3 Scanning electron microscopy and focused ion beam milling ................................................................ 42

    4 Platform for self-assembled structures 45

    4.1 The sacrificial layer.................................................................................................................................................. 45

    4.2 The hydrogel layer ................................................................................................................................................... 46

    4.3 The polyimide layer ................................................................................................................................................. 48

    4.4 The polyimide for bi-layer lift-off process ..................................................................................................... 51

    4.5 The frame solution ................................................................................................................................................... 51

    4.6 The encapsulation solution .................................................................................................................................. 52

    5 Results and Discussion 55

    5.1 Modelling of the compact helical antenna ..................................................................................................... 55

    5.1.1 Definition of parameters and 3D geometry of an electromagnetic environment ......................... 56

    5.1.2 Helical antenna layout and optimization of geometrical parameters ............................................... 56

    5.1.3 Targeting in-vivo implant applications ............................................................................................................. 61

    5.1.4 Self-assembly of helical antennas from the planar state ........................................................................... 65

    5.2 Experimental realization of com

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