A fully integrated SPAD sensor with photoluminescent encapsulation and die-bonded μLEDs for implantable oxygen monitoring

Continuous monitoring of oxygen concentration in biological tissue is critical for adaptive therapies and long-term implant diagnostics. This work presents a heterogeneously integrated photoluminescent oxygen sensing system combining CMOS single-photon avalanche diodes (SPADS) with pulse- and current-controllable micrometer-sized LEDs (μLEDs) die-bonded onto the chip. A single-step encapsulation using an optically active polymer integrates both the sensing and protecting layers. The system achieves a concentration resolution of 0.03 to 0.5 % O2 with an energy consumption of 73.4 nJ per measurement at up to 6.6 ksps, outperforming state-of-the-art systems by 3x in accuracy, 20x in sampling rate, and requiring only one-third of the power.

Subjects

CMOS sensor integration

LED driver circuits

photoluminescence lifetime sensing

Single-photon avalanche diode (SPAD)

DDC Class

537: Electricity and Electronics

572: Biochemistry

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A fully integrated SPAD sensor with photoluminescent encapsulation and die-bonded μLEDs for implantable oxygen monitoring