Four years, a handful of dedicated colleagues and nearly a dozen patents later, Mr. Duffy has brought the idea to life with Everence, a product he and his partners hope will deepen bonds — in the most literal and physical way — between family, friends and loved ones.

It is about as biologically intimate as one can get. Everence is a powdery substance synthesized from a sample of DNA, something as simple as a few thousand cells from a swab of a person’s inner cheek, or from cremated ashes. A small vial of Everence can be brought to a tattoo artist and added to any type of inks.

The result: A tattoo imbued with the DNA of another human being — or, if you prefer, a dog, cat or other furry friend.