Sampling of fluid through skin with magnetohydrodynamics for noninvasive glucose monitoring

Abstract

Out of 463 million people currently with diabetes, 232 million remain undiagnosed. Diabetes is a threat to human health, which could be mitigated via continuous self-monitoring of glucose. In addition to blood, interstitial fluid is considered to be a representative sample for glucose monitoring, which makes it highly attractive for wearable on-body sensing. However, new technologies are needed for efficient and noninvasive sampling of interstitial fluid through the skin. In this report, we introduce the use of Lorentz force and magnetohydrodynamics to noninvasively extract dermal interstitial fluid. Using porcine skin as an ex-vivo model, we demonstrate that the extraction rate of magnetohydrodynamics is superior to that of reverse iontophoresis. This work seeks to provide a safe, effective, and noninvasive sampling method to unlock the potential of wearable sensors in needle-free continuous glucose monitoring devices that can benefit people living with diabetes.

End-to-end design of wearable sensors

“…One challenge for prolonged continuous use is that the amount of fluid extracted through reverse iontophoresis is limited by the amount of current applied to the skin, with higher currents causing irritation and pain. An alternative magnetohydrodynamic approach has been used to extract ISF in a non-invasive manner, allowing for faster extraction with reduced irritation when compared with reverse iontophoresis 80 .…”

Influence of Enzyme Immobilization and Skin-Sensor Interface on Non-Invasive Glucose Determination from Interstitial Fluid Obtained by Magnetohydrodynamic Extraction

“…in Table S 2). The concentration of glucose extracted with MHD is 30-140 μmol/L (Hakala et al, 2021) for the porcine skin model and may be lower for human skin. Consequently, electrochemical techniques match the required analytical performance imposed by the extraction method.…”

“…Recently, we reported (Garcia Perez et al, 2019;Hakala et al, 2021) that when a magnetic field is applied locally and in combination with an electric field, it induces a Lorentz force that transports interstitial fluid to the skin surface. The phenomenon is called magnetohydrodynamic (MHD) extraction.…”

“…In our previous work, ca. 0.5 μL of interstitial fluid was typically extracted with MHD into a larger electrolyte volume, which was then analyzed using a spectrophotometric assay (Hakala et al, 2021). In this work, we integrated MHD extraction with the electrochemical detection of glucose due to the following advantages over optical techniques.…”

Point-of-care and self-testing for potassium: recent advances

“… 60 Also, ISF extraction can be done using sonophoresis, which employs an ultrasound to increase the permittivity of the skin to the ISF, 61 and magnetohydrodynamics which induces ISF flow via external magnetic and electric fields. 62 Those methods are still in early stages and have been mostly demonstrated for glucose measurement. Commercially, Kiffik Biomedical (US) 63 is developing a method of obtaining continuous access to ISF, which works by forming stable microopenings through the epidermis.…”