Generally a signature means the signing of a written document with one's own hand but it's not usually required that a signature actually be written by hand for it to be legally valid. For example, it can be typed, engraved, or stamped. The purpose of a signature is to authenticate a writing, or provide notice of its source, and to bind the individual signing the writing by the provisions contained in the document.
I can't find anything specific to loans but Section 3-401(b) of the UCC (O.C.G.A 11-3-401(b)) says that a "signature may be made (i) manually or by means of a device or machine; and (ii) by the use of any name, including a trade or assumed name or by a word, mark, or symbol executed or adopted by a person with present intention to authenticate a writing." I imagine that it would be the same for a loan agreement.
Your only problem would arise if you have to prove that the signature is authentic in court. That's generally why you have signature notarized.