Octiv Suite Publications

Octiv Suite: Theory of Operation

M Hopkins, D Gahan

Published 26 Sept 2014

Abstract

The Octiv Suite is part of a range of products which measure the parameters of plasma power delivery. These parameters include; real power; forward power; reflected power; impedance; voltage; current; phase angle; harmonics and ion flux. The Octiv Suite is also capable of reconstructing the waveforms of multiple fundamental frequencies simultaneously. The measurement functionality of the Octiv Suite extends to time-averaged, time-resolved and time-trend measurements.

Download at Theory of Operation: Octiv Suite


The injection of microorganisms into an atmospheric pressure rf-driven microplasma

P.D. Maguire, C.M.O. Mahony, D. Diver, D. Mariotti, E. Bennet, H. Potts, D.A. McDowell

Published 3 Oct 2013

Abstract

The introduction of living organisms, such as bacteria, into atmospheric pressure microplasmas offers a unique means to study certain physical mechanisms in individual microorganisms and also help understand the impact of macroscopic entities and liquid droplets on plasma characteristics. We present the characterization of an RF-APD operating at 13.56MHz and containing microorganisms in liquid droplets emitted from a nebulizer, with the spray entrained in a gas flow by a gas shroud and passed into the plasma source. We report successful microorganism injection and transmission through the plasma with stable plasma operation of at least one hour. Diagnostics include RF electrical characterization, optical emission spectrometry and electrostatic deflection to investigate microorganism charging. A close-coupled Impedans Octiv VI probe indicates source efficiencies of 10 to 15{\%}. The introduction of the droplets/microorganisms results in increased plasma conductivity and reduced capacitance, due to their impact on electron density and temperature. An electrical model will be presented based on diagnostic data and deflection studies with input from simulations of charged aerosol diffusion and evaporation.

Online at Abstract ID: BAPS.2013.GEC.MR1.59


Defining Plasma Polymerization: New Insight Into What We Should Be Measuring

Andrew Michelmore, Christine Charles, Rod W. Boswell, Robert D. Short, and Jason D. Whittle

Published 12 June 2013

Abstract

External parameters (RF power and precursor flow rate) are typically quoted to define plasma polymerization experiments. Utilizing a parallel-plate electrode reactor with variable geometry, it is shown that these parameters cannot be transferred to reactors with different geometries in order to reproduce plasma polymer films using four precursors. Measurements of ion flux and power coupling efficiency confirm that intrinsic plasma properties vary greatly with reactor geometry at constant applied RF power. It is further demonstrated that controlling intrinsic parameters, in this case the ion flux, offers a more widely applicable method of defining plasma polymerization processes, particularly for saturated and allylic precursors.

Online at ACS Appl. Mater. Interfaces, 2013, 5 (12), pp 5387–5391 DOI: 10.1021/am401484b


The link between mechanisms of deposition and the physico-chemical properties of plasma polymer films

Andrew Michelmore, David A. Steele, David E. Robinson, Jason D. Whittle and Robert D. Short

Published 23 May 2013

Abstract

Film thickness and functional group retention are routinely measured parameters for plasma polymers. It is known that other parameters such as density, solubility and mechanical properties can affect the performance of the plasma polymer film, however such parameters are not often measured; nor is there any understanding of the link between the mechanisms of film growth and these properties. In this investigation we produced thin films from three classes of commonly used plasma polymers (hydrocarbons, glymes and carboxylic acids). By choosing the monomer structure and applied RF power, the dominant mechanism of film growth was varied between ionic deposition and neutral grafting. The density, solubility and modulus of the resulting films were then measured by atomic force microscopy. Films grown from saturated monomers had higher moduli, were less soluble, and surprisingly had lower density compared to their unsaturated analogues. The results demonstrate that cognizance of the mechanism of film growth allows the physical properties of the film to be tailored for specific applications.

Online at Soft Matter, 2013,9, 6167-6175 DOI: 10.1039/C3SM51039E


On the Effect of Monomer Chemistry on Growth Mechanisms of Nonfouling PEG-like Plasma Polymers

Andrew Michelmore, Petra Gross-Kosche, Sameer A. Al-Bataineh, Jason D. Whittle, and Robert D. Short

Published 2 February 2013

Abstract

It has been shown that both ions and neutral species may contribute to plasma polymer growth. However, the relative contribution from these mechanisms remains unclear. We present data elucidating the importance of considering monomer structure with respect to which the growth mechanism dominates for nonfouling PEG-like plasma polymers. The deposition rate for saturated monomers is directly linked with ion flux to the substrate. For unsaturated monomers, the neutral flux also plays a role, particularly at low power. Increased fragmentation of the monomer at high power reduces the ability of unsaturated monomers to grow via neutral grafting. Chemical characterization by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirm the role that plasma phase fragmentation plays in determining the deposition rate and surface chemistry of the deposited film. The simple experimental method used here may also be used to determine which mechanisms dominate plasma deposition for other monomers. This knowledge may enable significant improvement in future reactor design and process control.

Online at Langmuir, 2013, 29 (8), pp 2595–2601 DOI: 10.1021/la304713b