A 3D implantable microsystem for intraocular pressure monitoring using a glass-in-silicon reflow process

This paper describes an implantable microsystem being developed to continuously monitor intraocular pressure. The glass-in-silicon reflow process allows the formation of an embedded cavity and a variety of device shapes. A 0.18µm CMOS circuit fits within the cavity and uses vertical feedthroughs in the glass to interface with other components. An optical trigger wakes up the IC to take data, reducing idle-mode power consumption to 50pW. The glass package allows the possibility of solar energy harvesting and provides haptics that facilitate implantation and allow explantation without tissue damage. The final microsystem will incorporate a microprocessor, microbattery, pressure sensor, and antenna.