A degradable device for minimally invasive blood sampling

Capillary blood sampling plays a crucial role in diagnostic decentralization, yet most existing microsampling devices remain prohibitively expensive, restricting their use mainly to developed countries1. To make this procedure more user-friendly, particularly for children, and accessible in low- and middle-income countries (LMICs), we recently developed an open-source, cost-effective silicone device capable of extracting a small volume of capillary blood within minutes. Inspired by the anatomy of sanguivorous leeches, our device ensures strong skin adhesion and generates high negative pressure to facilitate blood withdrawal2. Nevertheless, the presence of non-degradable components (i.e., silicone device and stainless-steel microneedles), similar to the existing blood sampling technologies, contributes to hazardous medical waste, a growing concern, especially in LMICs due to insufficient waste disposal infrastructure3. To address this challenge, we have developed a fully degradable blood sampling device. The device body was fabricated via digital light processing (DLP) 3D printing using tailored methacrylate biodegradable poly(D,L-lactide-co-ε-caprolactone) (poly(CL-LA)) copolymers. Similar to our previously reported silicone-based version, the printed copolymers exhibit good elastic self-recovery, enabling the compressed structure to generate sufficient negative pressure and skin adhesion, critical features for capillary blood extraction. A biodegradable microneedle (MN) patch, fabricated from coated magnesium blades, was integrated into the device, and its puncture performance was validated ex vivo using freshly excised porcine ear skin. After assessing the blood compatibility of both the 3D-printed device and MN patch through a hemolysis assay, a final prototype was assembled. Ex vivo and in vitro testing confirmed that the device effectively penetrated the porcine skin to a depth sufficient for accessing the capillary network and extract ca. 668 μL of porcine whole blood. Finally, degradation studies demonstrated full disintegration of poly(CL-LA) under composting conditions within 60 days, and complete Mg degradation in aqueous buffer. All together, these findings underscore the potential of this degradable device for sustainable capillary blood collection, particularly in resource-limited settings.