2026 Theses Doctoral

Micron-scale CMOS optical tags

Ramakrishnan, Girish

In this thesis, we introduce a platform for autonomously powered micron-scale CMOS motes. These motes are 30𝜇𝑚×30𝜇𝑚×10𝜇𝑚 in size - of the order of single-celled organisms and are fully bulk CMOS compliant. At these size scales significant challenges in power delivery, telemetry and handling require new innovative solutions to address.

The design of these motes is enabled by three design pillars - Ultra-low power CMOS design, a novel thin-film fluorescent modulator process and design, and a chip-scale bulk processing method to define and release micron scale motes from a millimeter scale substrate. The released motes are fully autonomous and are optically powered. They employ an optical fluorescent link for one-directional telemetry. The volume of the released motes is 9 picoliters and represent the state of the art for autonomous wireless CMOS devices. Insights are presented in this thesis for the IC design trade-offs for these motes and microfabrication methods are presented to manufacture these motes at scale. These methods are completely bulk CMOS compliant and are easily translate-able to other bulk CMOS mote designs with different scopes and functionality.

Finally we demonstrate the working of a released autonomous mote design in solution, incorporation into cells and present a method to interrogate these motes at scale using conventional epifluorescent microscopy.