3D-printed solid-contact chloride sensor for sweat-based cystic fibrosis screening

Cystic fibrosis (CF) is a genetic disorder marked by impaired chloride transport, with elevated sweat chloride concentration serving as the primary diagnostic biomarker. Here, we report a 3D-printed chloride-selective ion-selective electrode (3Dp-Cl^--ISE) for sweat chloride analysis relevant to CF screening. This work introduces a solvent-free, 3D-printed solid-contact chloride ISE that integrates a photocurable non-polyvinyl chloride selective membrane with a carbon-cloth transducer. The sensor combines a stereolithography (SLA)-printed membrane with a porous, hydrophobic carbon cloth substrate that functions as a capacitive electron reservoir, promoting efficient ion-to-electron transduction, suppressing water-layer formation, and enhancing potential stability. The fully integrated 3Dp-Cl^--ISE exhibits a Nernstian response (-55.3 mV/decade) over a physiologically relevant chloride concentration range (15.6-250 mM), covering the chloride range relevant to CF sweat-test interpretation. Selectivity studies demonstrate minimal interference from common sweat anions, including bicarbonate and lactate. The sensor was evaluated in commercially sourced human sweat using spike-and-recovery experiments across chloride concentrations relevant to CF screening, accurately quantifying spiked chloride concentrations spanning the clinically relevant screening range, including concentrations above 60 mM Cl^-. Together, these results demonstrate a durable, low-drift, and sweat-compatible sensing platform that leverages additive manufacturing to enable customizable, low-cost, and scalable chloride sensing, highlighting its potential for future point-of-care implementation and noninvasive monitoring of cystic fibrosis.