I'm currently employed as a R&D chemical/materials engineer with almost two years of experience. I plan to quit my job soon and take 6-9 months to self-teach myself advanced engineering concepts and to develop certain skills I’ll need to succeed in my career. I have a well thought out plan on how to accomplish this and have concluded that the benefits of doing this far out way the risks. However, I want to minimize the risk of not being able to find a job in 6-9 months considering the stereotype that HR/hiring managers have of unemployed applicants. What are some inexpensive but good online engineering certificates/programs, ideally related to materials/chemical engineering, that would act to supplement the job gap on my resume? Taking classes through a university is not currently an option. I have BS in chemical engineering and a passion for the development of advanced materials, especially catalysts.