According to the Catholic Church, can a tattoo be considered a sacramental?

Sacramentals are defined in 1917 canons 1144-5 (cf. 1983 canons 1166-7):

1144. The Sacramentals are objects or actions resembling the Sacraments which the Church makes use of by way of intercession to obtain especially spiritual effects.
      _{[Latin:] Sacramentalia sunt res aut actiones quibus Ecclesia, in aliquam Sacramentorum imitationem, uti solet ad obtinendos ex sua impetratione effectus praesertim spirituales.}

1145. The Apostolic See alone can institute Sacramentals, authentically interpret those in use, or abolish or change some of them.
      _{[Latin:] Nova Sacramentalia constituere aut recepta authentice interpretari, ex eisdem aliqua abolere aut mutare, sola potest Sedes Apostolica.}

So, no, tattoos cannot be considered sacramentals because the Apostolic See has not considered them as such.

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Also, as attested in ch. 5 of his autobiography, Bl. Henry Suso, O.P., inscribed the Name of Jesus into his breast with a stylus, but there is no indication that he or anyone else considered it a sacramental. It seems for him to have had the effects of a sacramental, conferring grace not ex opere operato ("from the work performed," as in the sacraments) but ex opere operantis (from his pious dispositions, as in the sacramentals).

I have a tattoo of Mary, I summoned a priest to be there during the whole process, he blessed the machine for use, the artist, me and the ink, upon completion the art got blessed as well with holy water. While he didn't confirm this would be considered as a sacrament he approved the process itself. I still wear my cross and medals at all times. For me it was a tribute no one ever can take away from me and that was its meaning.

Interestingly, the only time the word medals is mentioned in the ARTICLE 1 - SACRAMENTALS of the CCC is under the Popular Piety section,

(italic is mine)

Popular piety

1674 Besides sacramental liturgy and sacramentals, catechesis must take into account the forms of piety and popular devotions among the faithful. The religious sense of the Christian people has always found expression in various forms of piety surrounding the Church's sacramental life, such as the veneration of relics, visits to sanctuaries, pilgrimages, processions, the stations of the cross, religious dances, the rosary, medals, etc.

This paragraph is giving the impression that not even medals can be considered sacramentals!

There is also an etc in the end of the paragraph sufficiently ambiguous.

Better consult the Compendium of the CCC

(italic is mine)

351. What are the sacramentals?

1667-1672 1677-1678

These are sacred signs instituted by the Church to sanctify different circumstances of life. They include a prayer accompanied by the sign of the cross and other signs. Among the sacramentals which occupy an important place are: blessings, which are the praise of God and a prayer to obtain his gifts, the consecration of persons and the dedication of things for the worship of God.

Can a tattoo be considered a thing? Don't know.

Better ask a "tattooed millennial priest":

Can tattoos be sacramentals? [Article from the CNA]

“Sacramentals, used well, keep us close to the grace of Christ given to us in the seven sacraments, and receive their graces by the authority that Christ gives his bride, the Church, when she asks for his help. When the Church asks Christ for graces, He never refuses his bride,”

and

“This means that sacramentals only work when they are done according to the rules of the Church. If we want to ask Christ for these graces, we need to make sure we do so authentically as the Church, obediently accepting the rules she sets down. It's clear in Canon Law that the Apostolic See alone has the authority to establish sacramentals and define the criteria for their use [c. 1167],”

and

"However, he added, it is possible that tattoos could be “sacramentals” in a broader sense of the word."

which means in a strict sense they are not.

He keeps talking,

“A permanent image, engraved on the skin, could certainly serve as a constant, physical reminder of our new life in Christ. The image of a rosary, a cross, or other sacramental on our skin could lead us frequently to pray, to desire the seven sacraments more, and to think and act in communion with the Church,” he said.

and finally,

“So, while a tattoo could not fulfill the requirements to be a proper sacramental in itself, if used in discernment and good faith it could certainly provide similar benefits and be helpful in the pursuit of holiness.”

And here we have the confirmation that tattoos can not be considered sacramentals.

I can't confirm a tattoo can be blessed without being considered a sacramental.