Is it permissible for the husband to spend his wife's entitlements from the financial grant allocated for scientific research through one of the students, or by indirect means, given that she works in the same field and conducts research for him, but cannot be officially appointed?

You must refer to the university's regulations. If they prohibit a professor from employing relatives, then he is not permitted to assign you research or disburse university funds to you as payment for it, due to Allah's saying: (O YOU WHO HAVE BELIEVED, FULFILL [YOUR] CONTRACTS). If the regulations permit it, then you are allowed to receive payment. Any sensitivity can be avoided by declaring the matter and documenting the research and the amounts paid. However, issuing a check in the name of a student and then transferring the amount to you is an illegitimate method involving deception, and it could put your husband in a vulnerable position if discovered.