A Portable and Dual-Button Microneedle Device Enables Intelligent Multimodal Laser Sensing

This study developed a portable dual-button microneedle device for rapid collection of interstitial fluid and subsequent multimodal molecular and elemental analysis. The system combines a reusable mechanical applicator with disposable SLA-printed hollow microneedles containing integrated microfluidic channels and an Au nanocube/MXene sensing module. Pressing the first button inserts the microneedles into skin, while a second button releases a spring-loaded mechanism to retract them after approximately one minute of sampling. Mechanical characterization showed reproducible artificial-skin penetration and demonstrated that microneedles incorporating an oblique channel design resisted compression more effectively than conventional straight-channel tips, with lower displacement at equivalent force. COMSOL simulations supported the experimental findings by showing reduced stress transfer into the thin channel wall of the oblique design. The microneedles successfully penetrated a 2% agarose artificial-skin model and approximately 600 µm into rat skin, with visible puncture marks largely resolving within about one hour. The collected interstitial fluid was analyzed using surface-enhanced Raman spectroscopy for molecular biomarkers and laser-induced breakdown spectroscopy for elemental biomarkers. The sensing platform showed strong calibration linearity for representative analytes including 6-mercaptopurine and lithium, while animal pharmacokinetic experiments demonstrated that temporal changes measured in interstitial fluid followed trends observed in plasma. A convolutional neural network combining SERS and LIBS data achieved an overall classification accuracy of 0.885, with precision, recall, and F1 scores of 0.887, 0.891, and 0.888, respectively. Overall, the study integrates mechanically robust 3D-printed microneedles, microfluidic sampling, multimodal laser spectroscopy, and AI-based data processing into a low-cost point-of-care platform for minimally invasive health and drug monitoring.