Shivi Brian Neil, 21, of Pottstown was arrested on Friday and charged in the robbery at a Rite-Aid store in Wyomissing.
Police say they identified the Penn State - Berks student by a fingerprint left at the robbery scene.
Investigators say Neil is also being interviewed in connection with one other robbery, and other police departments are currently working on charges.
Surveillance video of the Sunday afternoon robbery in Wyomissing was released earlier this week. The video shows a thief handing the pharmacy clerk a note demanding prescription painkillers.
The note also informs the clerk that the bandit is armed with an HIV-infected needle.
"If she did not comply, or made a phone call or did anything other than submit to his demands, he would stick her with a syringe which was allegedly infected with HIV," said Wyomissing Police Chief Jeffrey Biehl earlier this week.
A few days earlier, surveillance cameras captured images of a man wearing a similar outfit, committing the same crime at the CVS in Lower Pottsgrove Township, using a very similar threat.
"With the demand note, he threatened the pharmacy tech and the pharmacist with that note and made off with drugs," said Lower Pottsgrove Police Lieutenant Michael Foltz.
The note used in the Lower Pottsgrove robbery also claimed he was carrying a gun. But neither a firearm nor a syringe was seen during these crimes.