funding - Is offering to use personal funds for research a good idea?

I'm at an engineering department at a public US university, and I'm somewhat new to writing proposals. The call I'm submitting to wants know if the project budget is higher than the amount of the grant, what other sources of funding the PI will use, presumably to ensure the success of the project.

First, I'm not rich. But this leads to me to think, is it okay to use personal funds to do research? For example, if a piece of equipment costs $4000 and I only have $3950 left, can I supplement it with personal funds?

What might end up happening is that I might convince a colleague to lend me his instrument. But I don't want to say this in the proposal. Also, I'm not sure saying the project will be "supplemented by personal funds" is a good idea.