Macroporous-channel hollow microneedles enable vacuum-free interstitial fluid sampling and on-patch sensing

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Microneedle (MN) devices for interstitial fluid (ISF) sampling show promise for point-of-care diagnostics.
• Existing MN technologies often face challenges with low extraction flux and complex fabrication.
• Vacuum-free ISF sampling is desirable for simplifying device design and improving patient comfort.

Purpose of the Study:

• To develop novel macroporous-channel hollow microneedles (MPC-HMNs) for efficient, vacuum-free ISF extraction.
• To integrate multiscale capillarity within the microneedle architecture to drive ISF sampling.
• To enable on-patch analysis of ISF using integrated sensing modules without external pumps or tubing.

Main Methods:

• Fabrication of MPC-HMNs using a single-step photopatterning process, incorporating a rigid shell, porous network, and axial lumen.
• Integration of MPC-HMNs with paper-wick collectors and on-patch electrochemical (potentiometry, amperometry) and colorimetric sensing modules.
• Evaluation of ISF extraction yield, start-up time, and analytical accuracy using ex vivo skin models and in vivo rat studies.

Main Results:

• MPC-HMNs demonstrated ISF yields and start-up times comparable to negative-pressure collectors.
• On-patch sensors accurately quantified electrolytes (potassium) and metabolites (glucose, acetoacetate, creatinine) in ISF.
• ISF measurements showed agreement with paired blood measurements for key analytes.

Conclusions:

• The developed MPC-HMN architecture effectively utilizes multiscale capillarity for vacuum-free ISF sampling.
• The integrated system simplifies device complexity, enabling disposable, compact formats for near-patient monitoring.
• MPC-HMNs offer a practical and minimally invasive approach for real-time health status assessment.