Session: 03-04-03: Advanced Machining and Finishing Processes

Paper Number: 116611

116611 - The Effect of Pulsed Power During Electrochemical Surface Modification on the Wettability of Aluminum and Titanium Alloy 

Used in industries ranging from military to biomedical, aluminum and especially titanium alloy have become the focus of many studies due to their high strength to weight ratio and biocompatibility. Titanium's surface properties (surface energy and wettability) are particularly interesting due to its use as an implant. Implants need to have a hydrophilic nature when tissue growth is desired, while they need to be hydrophobic if tissue/microbial growth is not expected. Thus there is a need to control the wettability of these metals. This study used a sodium chlorate electrolyte to control the wettability of aluminum and titanium alloy samples using an electrochemical surface modification (ECSM) process. This was achieved by building a custom-made electrochemical system. One significant advantage of ECSM over other surface modification methods is that the wettability can be controlled without using a secondary polymer coating or toxic acids as chemical etchants. While ECSM is typically performed using DC power, pulsed power offers better control over the process and unique results leading to controlling the wetting nature of the surface. A full factorial designed experiment was performed to understand the influence of the pulsed voltage on the surface properties. In this study, duty cycle, frequency, and ECSM duration were modified while voltage was held constant to determine their effect on the surface's wettability. Duty cycles of 25%, 50%, 75%, and 100% (or DC) and frequencies of 1 kHz and 100 kHz were used while voltage remained at 10 V. Time was changed for each duty cycle to allow the sample to have an equal active time with 2000, 1000, 667, and 500 seconds for 25%, 50%, 75%, and 100% duty cycles, respectively. Surface roughness was measured before sanding and cleaning, after sanding and cleaning, and after ECSM post heat treatment. Contact angles were measured using the sessile drop test and ranged from near zero degrees (super hydrophilic) to greater than 90 degrees (super hydrophobic), respectively. A first principles-based theoretical model was developed in this study to predict the pulse power setting needed to achieve the desired wettability in the samples by measuring the sample mass before and after ECSM. It is important to note that the mass after ECSM was measured only after the evaporation of any residual water. The model was validated with experimental results. An efficiency factor was introduced into the model to account for the energy loss due to thermal inefficiencies. It was noted that the surface's wettability switched from hydrophilic to hydrophobic after the sample was heated in a furnace. This is believed to be due to the evaporation of the residual water in the micro and nano structure created by the ECSM process. Minor differences in the wettability were noted in the effect of ECSM on aluminum samples compared to titanium alloy. Still, both the metals showed a similar trend in contact angle behavior after evaporation of the residual water. This study allows for the use of ECSM as a technique to modify the surface of implants with controlled wettability for improved osseointegration.

Presenting Author: Anton Petrenko Grand Valley State University

Presenting Author Biography: Anton Petrenko is a graduate student working on his master’s degree in biomedical engineering with an electrical emphasis at Grand Valley State University (GVSU). He received his undergraduate degree in biomedical sciences with a minor in chemistry from GVSU. After working in the hospital for a few years, he switched to biomedical engineering. Anton enjoys golfing, camping, working out, and other active outdoor recreation in his free time.

Authors:

Anton Petrenko Grand Valley State University
Abishek Balsamy Kamaraj Grand Valley State University