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Course of studies
One-pot synthesis of micron partly hollow anisotropic dumbbell shaped silica core–shell particles
(2016)
Parylene-C is used for various biomedical devices because of its high conformity and biocompatibility. However, delamination could occur because of low adhesion between Parylene-C and other materials. For this experiment 4-inch Si-wafers are used. Parylene is deposited by chemical vapour deposition (CVD). Silane A-174 as adhesion promoter is added between Parylene-Parylene layers. The samples are soaked at different duration 1 h, 24 h and 120 h in PBS solution at 37 °C. A peel test is further performed to investigate the adhesion properties of the samples.
The paper shows the influence of low-pressure plasma on polyethylene terephthalate (PET) to achieve improved layer adhesion between PET and ALD multilayers. The literature describes a relationship between functional groups that are incorporated into the polymer surface and better layer adhesion. In this work, the relative number of functional groups after treatment on the surface of PET was measured by the surface energy.
The PET film Hostaphan® RNK was exposed to oxygen and argon plasma with varying treatment times. Subsequently, the surface energy was determined via the contact angle measurement.
The investigations have shown that with increasing treatment time in the oxygen plasma, an increasing surface energy is associated, which is due to the increased incorporation of functional groups, such as hydroxy groups. Furthermore, the results have confirmed the thesis that if the plasma treatment is too long, oxidation takes place on the polymer surface and thus the surface energy decreases. Another aspect that has emerged in the results of the study is the subordinate role of the power of the plasma.
Since the study has not proven the connection between a good layer adhesion, of ALD multilayers on PET, and a high surface energy, this work should serve as an indication for the investigation of this thesis.
In the present work, polyetheretherketone (PEEK) was pretreated with oxygen plasma to investigate the influence on the contact angle and surface energy. For this purpose, PEEK samples were fabricated over several manufacturing steps, which were used as substrates for later investigations. A series of measurements was performed at a power of 300 W for different treatment durations and the contact angle of H2O on the PEEK surface was determined. The results show that plasma pretreatment significantly affects the surface modification of PEEK disks. The best hydrophilic properties of the PEEK surfaces were measured at a treatment time of 540 s and a power of 300 W. A much longer treatment time caused the correlated values of contact angle and surface energy to increase and in this case an excessive treatment time did not contribute to a further increase in hydrophilicity.
Investigation on adhesion strength of Parylene-C coatings with different adhesion promotion methods
(2021)
Delamination of encapsulation materials (here the polymer Parylene-C) is one of the biggest failure mechanisms for active medical implants. This problem is addressed by the application of different pre-treatment and adhesion promotion methods. The methods applied in this research are oxygen and Silane A-174 solution pre-treatment and Silane A-174, titanium oxide and Trimethylsilane as adhesion promoters. The adhesion forces of these methods are quantified after different soaking times in phosphate buffered saline (PBS) solution to mimic environment of the human body.