Water‐Resistant Conformal Hybrid Electrodes for Aquatic Endurable Electrocardiographic Monitoring

Abstract

Preparation of Au/PDMS films: PDMS films were prepared from Sylgard 184 Silicone Elastomer Kit (Dow Inc.). A mixture of precursor and crosslinker at 10:1 ratio was spin coated on a fluorinated silicon wafer at 800 rpm for 60 s, and cured 60 o C for 5 h. The prepared PDMS films were around 70 μm thick. Au nanolayers were deposited by a vacuum thermal evaporator (Nano 36, Kurt J. Lesker) under 2×10 -6 Torr with a deposition rate of 0.3 Å/s. The Au source was purchased from Kurt J. Lesker and the purity was 99.99%. The deposition time was controlled to get 80 nm thick gold layers.Synthesis of dopamine methacrylamide (DMA) monomer: DMA monomer was synthesized according to the previously reported method. [S1] 10 g of sodium tetraborate and 4 g of sodium bicarbonate were dissolved in 100 mL deionized water and bubbled with nitrogen for 20 min.With continuous nitrogen flow, 5 g of dopamine hydrochloride (26.4 mmol) was dissolved in the solution. Then 5 mL of methacrylate anhydride (94 % purity, 29.1 mmol) in 20 ml THF was added dropwise, during this process the pH was kept above 8 with the addition of 1 M sodium hydroxide. The mixture was stirred overnight at room temperature. The reaction mixture was washed twice with 50 mL ethyl acetate, and then the pH of the aqueous solution was changed to less than 2 and extracted with 50 mL of ethyl acetate three times. The ethyl acetate layers were combined and dried over sodium sulfate, evaporated to reduce to around 30

A Compliant Ionic Adhesive Electrode with Ultralow Bioelectronic Impedance

“…Ionic conduction in the biological system plays a central role in the transmission of vital signs and performing physiological activities, such as the transmission of nerve signals, muscle contraction, heart beating, and blood pressure control. [ 1–24 ] Highly efficiently and precisely collecting or delivering these ionic signals are of great interest in clinical neurophysiology and material science for future wisdom medical and AI device controlling. [ 1,25–30 ] Therefore, an electrode that complies with the curved biological surface and has low bioelectrical interfacial impedance (the ideal impedance of electrode‐skin system is 6–10 kΩ which is the intrinsic impedance of skin) is in demand to effectively couple the ionic fluxes in electrolytic tissues and electronic current in recording devices.…”

A Solvent‐Free and Water‐Resistant Dipole–Dipole Interaction‐Based Super Adhesive

“…Design and fabrication of water‐resistant adhesives are important for practical applications in a water or wet environment. [ 37–40 ] Thus far, the adhesive strengths of most reported adhesives tend to suffer from deterioration with the increase of immersion time under water due to the water‐induced instabilities of polymer network structure as well as water infiltration into the interface. Therefore, creating an adhesive with an ability to maintain long‐term high‐strength adhesion under water remains a challenge.…”

Hydrogel facilitated bioelectronic integration

“…Similarly, hydrogels have found extensive applications in many other bioelectronic designs, such as electroencephalogram, electrocardiogram, transcutaneous electrical nerve stimulation, electronic skin, and highly stretchable wearable devices. [29][30][31] Different from skin, the integration of bioelectronic devices with internal biological systems typically requires invasive procedures, where immune responses and scar formation around electronics are common barriers to electrical recording and stimulation. Soft cells/tissues have a Young's modulus in the range of 0.5 to 100's of kPa, 32,33 whereas that of typical electronic materials (e.g.…”