How does this man sign a power of attorney for health care, in order to name his wife as the agent if only communicates by blinking?

Under Illinois Statute a Will must be signed by the testator or by some person in his presence and by his direction and attested in the presence of the testator by 2 or more credible witnesses. This means that another person may sign the Will on behalf of the paralyzed man (the testator). The witness acknowledgement should acknowledge the circumstances of the signature on the testator's behalf and that the testator had capacity to understand the Will and direct the signing of the Will on his behalf.