Multiplexed Label-Free Cytokine Sensing Using a 128x128 CMOS ISFET Array with Flexdym Microfluidic Partitioning

Abstract

Cytokine-mediated inflammation disorders such as sepsis and cytokine release syndrome demand bedside multiplex panels that resolve pro- and anti-inflammatory dynamics in minutes, yet label-free FET cytokine sensors remain limited to few devices, single analytes, and PDMS packaging that sorbs small molecules and leaches oligomers. We present a CMOS platform pairing a 128 x 128 ion-sensitive field-effect transistor (ISFET) array (SkyWater 130 nm, SiN gate) with a FlexDym 4 x 1 micro-well overlay that partitions the membrane into four chemically independent regions (approximately 2,176 pixels each, square-root-of-N averaging). Two wells carry capture antibodies (anti-IL-6, anti-IL-10), one is a non-specific reference, and one tests specificity; the transduced signal is defined as the differential current relative to the reference signal (Delta I_D(W_n) - Delta I_D(W_3)). Single-analyte dose-response measurements spanning 100 fM to 10 nM successfully resolve both IL-6 and IL-10 above the non-specific detection floor, including at healthy-serum baseline concentrations. The array shows a per-pixel pH sensitivity of 1.13 microamperes per pH unit (CV approximately 14%). Across two chips, device-to-device variation is dominated by transconductance spread (g_m CV approximately 62%); a one-time per-device g_m calibration reduces analyte-measurement variance to approximately 16%. We further validate the surface functionalization, characterize device-to-device variation, and demonstrate the FlexDym integration workflow. Simultaneous multiplexed cytokine measurements resolve IL-6 (W1) and IL-10 (W2) against the chemistry-only reference (W3). At the same time, cross-specificity characterization is assessed by applying IL-6 to an anti-IL-10 well (W4), establishing a scalable label-free ISFET architecture for multiplexed cytokine sensing.