For ME PhD admissions, better to have undergraduate research experience in just one lab or multiple?

I’m a sophomore right now, about to be a junior, in Mechanical Engineering, and I’d like to do a PhD when I graduate. I know schools look for undergrad research experience, so I’ve been working in a lab since spring semester of freshman year with a very good faculty adviser. He offers wonderful guidance and support, and I enjoy the lab community, but I don’t totally like the project I’m working on. It has a lot of focus in another field of science/engineering that I don’t want to go into for graduate school. Additionally, I don’t have the best grasp on this field, since it isn’t as related to ME as I’d like, so I feel like any contributions I can make are minimal and superficial.

I’d love to try to get into a project that I have a deeper understanding of and interest for with another faculty member at my uni (I actually have found a number of projects on other faculty’s websites that I am interested in), but I am concerned mainly about two things:

  1. Will the trade-off between “interesting project that I can contribute a lot to and fully invest myself in” and “very helpful and concerned research adviser that tries hard to get all of his students to succeed” be worth it? I suspect that no matter which faculty adviser I’d end up with, they wouldn’t be as invested in my success as the one I’m currently working under. I know many are too busy to even step into their labs the majority of the time.
  2. Will graduate schools see that I switched projects/labs and be concerned that I am inconsistent? I don’t want to give them the wrong impression, because I certainly want to and have the ability to commit to a project for a long time. I would just rather explore different areas of research before graduate school so that I could pick a program to apply to that is a better fit for me.

Ask your research mentor. This is the person who will have the greatest role in advising you.

Spend a summer or two doing an REU so that you have additional research recommendations.

Really it is just important that you have good experience, i.e. one where you learn something and the faculty member(s) are willing to write you strong recommendations. It’s also good to have relevant experience, so if you don’t like what you are doing, you can certainly consider switching. It won’t be held against you.