A Degradable Device for Sustainable Capillary Blood Sampling

Capillary blood sampling plays a crucial role in diagnostic decentralization, yet most microsampling devices remain expensive, limiting their use mainly to developed countries. To improve accessibility, a cost-effective silicone device capable of extracting small volumes of capillary blood in vivo was previoulsy developed by our group. However, the use of non-degradable materials poses limitations, especially in resource-limited settings with inadequate waste disposal infrastructure. Herein, a nearly fully degradable microsampling prototype is reported. The device body is fabricated using digital light processing 3D printing with tailored poly(ɛ-caprolactone-co-D,L-lactide). This device yields negative pressure and adhesion strength comparable to the original prototype, although it requires greater manual compression. In vitro, it collects ≈670 µL of porcine whole blood, matching the volume drawn by the silicone counterpart. The device is equipped with magnesium microneedle blades coated with poly(ɛ-caprolactone) to enhance blood stability. Degradation studies show complete disintegration of poly(ɛ-caprolactone-co-D,L-lactide) under composting conditions within 60 days, and near-complete degradation of magnesium blades in aqueous buffer within 40 days. Preliminary hemolysis assays confirm blood compatibility of both the 3D-printed device and coated microneedles, with sample quality preserved for up to 3 h. Altogether, these findings highlight the potential of this degradable prototype as a sustainable alternative for capillary blood collection.