The Shield tech item is a prototype of the shield made by dataDyne. It is found in dataDyne Laboratory Basement, as one of the objectives in DataDyne Research: Investigation. Dr. Caroll uses a similar shield in the next mission.
The shield protects the user by detecting an attack and momentarily generating a concentrated force-field to repel the attack. The shield has a limited reservoir of energy, so it can only protect the user to a certain extent. Shields are usually activated whenever the user is carrying them, although this particular shield appears to be a non-functional, near-complete prototype.