| AVS 60th International Symposium and Exhibition | |
| Advanced Surface Engineering | Wednesday Sessions |
| Session SE+PS-WeA |
| Session: | Atmospheric Pressure Plasmas |
| Presenter: | J.R.G. Schalken, Eindhoven University of Technology; InnoPhysics B.V., Netherlands |
| Authors: | J.R.G. Schalken, Eindhoven University of Technology; InnoPhysics B.V., Netherlands A.A.E. Stevens, InnoPhysics B.V., Netherlands P. Verhoeven, InnoPhysics B.V., Netherlands M. Creatore, Eindhoven University of Technology, Netherlands |
| Correspondent: | Click to Email |
The µPlasmaPrint technique utilizes a pin-to-plate dielectric barrier discharge at atmospheric pressure. A dielectric substrate is placed on a high-voltage plate electrode. An array of needles is moved above the substrate, while individual needles are allowed to move towards the surface and back based on a digital pattern. According to the Paschen law, a reduction of the distance between a grounded needle electrode and the high-voltage substrate holder from about 800 µm to 200 µm can lead to the ignition of a plasma. Within a millisecond the plasma is turned off by moving the needles up again. The dot-wise exposure of the surface to short micro-plasmas enables a local plasma treatment with a minimum feature size of 100 µm.
Thin films of plasma polymerized APTMS have been deposited on a fluorinated ethylene propylene copolymer (FEP) using the µPlasmaPrint technique. The thickness of the deposited films varied in the range of 5 to 100 nm. The surface characteristics and ageing behavior of the films have been investigated by X-ray photoelectron spectroscopy (XPS), fluorescence microscopy and water contact angle measurements, respectively. Depending on the number of print repeats of the µPlasmaPrint system, the concentration of amino-functionalities in the deposited film as derived from XPS peak analysis varied from 9.1% for a single print repeat, down to 4.7% for 20 print repeats.
Water contact angle measurements showed an increase from 10° for a single print repeat up to 40° for 20 print treatments, while the water contact angle of the FEP substrate was measured to be 110°. The increase in water contact angle with increasing print repeats suggested a reduction of polar components at the surface and was therefore consistent with the relative reduction of amino-functionalities as measured with XPS.
Based on the experimental results, a polymerization process of APTMS is proposed. It is suggested that polymerization mainly takes place by the abstraction of methyl– and methoxy– groups to develop siloxane chains. For an increased number of print repeats, which results in a prolonged plasma exposure, it is proposed that the creation of reactive sites for the cross-linking of APTMS polymer chains also takes place in the aminopropyl chains, resulting in a decreased concentration of amino-functionalities.