The mark of the beast has two properties that exclude the implant as the “mark of the beast”, even though it could certainly be used as part of that system.  The book of Revelation is fairly clear on the fact that,

1. The mark is visible on the forehead or right hand, and…
2. …that the mark is taken in order to submit to the ruling authority of the Antichrist.

Since the Antichrist is currently unrevealed, he cannot be in authority to demand tribute via any method, implant or not.  The fact that the church is still on earth is evidence that the Antichrist is unrevealed.  Even if he were to use an implant, and he likely will, anyone who does not have the visible mark or who has not “signed up” for the new order of things will not be able to use their implant to buys goods or services.

A primary reason for the mark, perhaps the main one, is to force the Jews into being easily identified by their lack of the visible mark.  Jews are forbidden under the Old Testament Law from putting anything on their foreheads or right hands other than the name of God.  It would be blasphemy for any Jew to put any name other than God’s name in this place.  This is the main reason that most Bible scholars insist that the mark is visible, aside from the fact that Scripture demands it.