The Structural Design and Experimental Analysis of a Microneedle with Microchannels: Capable of Achieving Ultrafast Body Fluid Extraction

In this study, microneedles (MNs) arrays with microchannels were prepared based on poly(vinyl alcohol) and hydroxyethylcellulose composite materials. The finite element method was adopted to optimize the size of microchannels and the needle tip by establishing the skin penetration model and the human interstitium fluid (ISF) extraction model. The results show that they are positively correlated with the stress during skin penetration. The extraction rate of ISF varies as a function of the microchannel size, initially increasing and then decreasing (with the peak extraction speed occurring at a diameter of 10 μm). Comprehensively considering the manufacture and structural strength, the MNs array with the extremely fast ISF extraction (45.0 ± 2.1 s) and excellent skin penetration ability was prepared (with the microchannel diameter of 4 μm and the needle tip diameter of 10 μm). Furthermore, the microchannel of MNs arrays prepared with soluble materials can continuously increase with the extraction of ISF, enabling it to have a faster extraction speed of ISF while also demonstrating the excellent skin penetration ability. This has halved the time for the MNs sensor to complete the detection. This work lays the foundation for the development of efficient ISF acquisition and the realization of in situ ISF detection technology.