Method of fabricating metasurface on skin for blood glucose detection
A method of fabricating metasurface on skin for blood glucose detection, which relates to a flexible wearable electronic technology in healthcare. The blood glucose detection comprises: designing metasurface with a resonant ring structure cell, and building a model by simulating a relationship between blood glucose concentration and electromagnetic absorption property of the metasurface; preparing the metasurface on the skin; scanning the metasurface on the skin under different frequencies electromagnetic wave and acquiring a relationship curve between S-11 parameter and frequency; the change of blood glucose concentration is determined according to the resonant peak frequency shift in the relationship curve based on the model. It realizes the electromagnetic wave metasurface with a good skin biocompatibility, a stable electromagnetic property and a high glucose detection accuracy is directly structured on the skin, moreover, it can directly measure human blood glucose concentration without sampling human blood, realizing real non-invasive human blood glucose detection.
1 . A method of fabricating metasurface on skin for blood glucose detection, comprising:
designing a metasurface with a resonant ring structure cell, and building a model by simulating a relationship between blood glucose concentration and electromagnetic absorption property of the metasurface;
preparing the metasurface on the skin;
scanning the metasurface formed on the skin and acquiring reflection spectra of the metasurface under electromagnetic wave with different frequencies, thereby obtaining a relationship curve between S-11 parameter (reflection coefficient) and frequency; and
determining change of blood glucose concentration as a function of resonant peak frequency shift in the relationship curve based on the model;
wherein the preparing the metasurface on the skin comprises:
preparing a stretchable composite conductive ink using preset liquid metal particulates, preset metal particles, and preset elastic resin;
printing the stretchable composite conductive ink onto water transfer paper by screen printing, and applying preset treating pressure against the stretchable conductive ink layer printed on the water transfer paper for a preset duration after the ink is dry, such that shells of the liquid metal particulates in the stretchable composite conductive ink layer are cracked, and liquid metal particulates in the shell flow out to connect adjacent metal particles, thereby obtaining the metasurface on the water transfer paper; and
transferring the metasurface on the water transfer paper onto the skin via a water transfer printing process, whereby to form the metasurface on the skin.
2 . The method of claim 1 , wherein the resonant ring structure refers to a split-ring-resonator structure with a round or square shape, and the split-ring-resonator structure has a linewidth ranging from 0.5 mm to 5 mm and a gap width ranging from 1 mm to 10 mm; and/or,
the electromagnetic wave has a wavelength at a millimeter level and a frequency ranging between 30 GHz and 300 GHz.
3 . The method of claim 1 , wherein in the stretchable composite conductive ink, the mass fraction of the liquid metal particulates ranges from 1% to 15%, the mass fraction of the metal particles ranges from 60% to 80%, and the mass fraction of the elastic resin ranges from 5% to 39%.
4 . The method of claim 3 , wherein the liquid metal particulates are selected from eutectic gallium-indium nanoparticles or eutectic gallium-indium-tin nanoparticles.
5 . The method of claim 4 , wherein the liquid metal particulates have a diameter ranging from 50 nm to 1000 nm.
6 . The method of claim 1 , wherein the metal particles are selected from at least one of silver microflakes, silver nanoflakes and silver microparticles.
7 . The method of claim 1 , wherein the elastic resin is selected from any one of polydimethylsiloxane, polyurethane, silica gel, styrene-butadiene-styrene block copolymer, and styrene-ethylene-butadiene-styrene block copolymer.
8 . The method of claim 1 , wherein the applying a preset treating pressure against the stretchable conductive ink layer printed on the water transfer paper to treat for a preset duration, such that shells of the liquid metal in the stretchable composite conductive ink layer are cracked, and the liquid metal particulates flow out to connect adjacent metal particles, thereby obtaining the metasurface on the water transfer paper, comprises:
applying a preset treating pressure ranging from 10N to 100N against the stretchable conductive ink layer printed on the water transfer paper and treating for 1 min to 2 min, such that shells of the liquid metal particulates in the stretchable composite conductive ink layer are cracked, and the liquid metal particulates flow out to connect adjacent metal particles, thereby obtaining the metasurface on the water transfer paper.
9 . The method of claim 1 , wherein the transferring the metasurface on the water transfer paper onto the skin in a water transfer printing process comprises:
wetting the metasurface on the water transfer paper with water, attaching the wet paper on the skin, and treating for 1 to 5 minutes under a pressure ranging from 10 Pa to 800 Pa, whereby to transfer the metasurface onto the skin.