3D Printing Silicone Elastomer for Patient-Specific Wearable Pulse Oximeter

Commercial pulse oximeters are used clinically to measure heart rate and blood oxygen saturation and traditionally made from rigid materials. However, these devices are unsuitable for continuous monitoring due to poor fit and mechanical mismatch. Soft materials that match the elastic properties of biological tissue provide improved comfort and signal-to-noise but typically require molding to manufacture, limiting the speed and ease of customizing for patient-specific anatomy. Here, freeform reversible embedding (FRE) 3D printing is used to create polydimethylsiloxane (PDMS) elastomer cuffs for use on the hand and foot. FRE enables printing liquid PDMS prepolymer in 3D geometries within a sacrificial hydrogel bath that provides support during cure. This serves as proof-of-concept for fabricating patient-specific pulse oximeters with pressure sensing, termed P-3-wearable. A sizing analysis establishes dimensional accuracy of FRE-printed PDMS compared to anatomical computer-aided design models. The P-3-wearable successfully outputs photoplethysmography (PPG) and pressure amplitude signals wirelessly to a tablet in real time and the PPG is used to calculate heart rate, blood oxygen content, and activity state. The results establish that FRE printing of PDMS can be used to fabricate patient-specific wearable devices and measure heart rate and blood oxygenation on par with commercial devices.