{
    "protocol": "Hydrogel coatings were prepared by first submerging clean medical surfaces in a benzophenone solution in ethanol. After removal of the solution, an aqueous pregel solution containing N,N-dimethylacrylamide (DMAA) and a biocompatible photoinitiator (Irgacure 2595) was added to the activated surfaces. UV irradiation was then applied to polymerize the hydrogel layer. Excess polymers and byproducts were thoroughly rinsed away, resulting in an ultrathin (approximately 10 µm) hydrogel layer uniformly coated on the device.The medical-grade flat surface or tubing was cut to the desired size, cleaned with isopropanol and DI water, and fully dried with a nitrogen stream. The devices were air-plasma treated for 1-2 min and submerged in a benzophenone solution (10 wt% in ethanol) for 3-5 min. The devices were then removed from the solution, and excess ethanol was removed by blotting with tissue. The devices were submerged in a hydrogel precursor solution (20-30 wt% N,N-dimethylacrylamide, 0.5 wt% Irgacure I-2959 in water). For flat surfaces, there should be at least 5 mm of precursor solution above the surface. For tubing, the precursor solution should completely fill the inner lumen. The devices were then exposed to UV (UVP CL-1000, λ=365 nm) for 45 min to create the interpenetrating hydrogel layer on the device surface. The polymerized solution was removed and disposed as waste. The devices were thoroughly washed with DI water for 3 days before testing."
}