Certain embodiments relate to a sprayer or other medical apparatus for applying a biocompatible coating in situ. Such an apparatus may have a first conduit connected to a first exit opening and a second conduit connected to a second exit opening to deliver a first composition through the first conduit and a second composition through the second conduit to mix the first composition and the second composition outside both the first conduit and the second conduit. The first composition may be, e.g., a precursor to a material formed after the mixing of the first composition and the second composition. The first exit opening and the second exit opening may be approximately adjacent to each other and define an angle that is less than about 140 degrees.