How do you motivate participants to take a survey?

I am a PhD student and I'm teaching a class. There are only seven graduate students in it. I am trying to gather data on a specific technology that I have included in my lesson delivery method through quantitative surveys. I need the survey results fast as I have to publish them in a conference paper soon. My students won't take the survey and so far I only have two responses. I feel like the students are not serious enough or simply does not like me for some reason. How do I motivate my students to take the survey? What would be an effective approach to reach out to them so that they will participate in the research? Note that the survey is completely voluntary and I cannot make them do anything.