I met a problem when coating the 96-well plate using poly-HEMA. I prepared 5 mg/ml poly-HEMA and mixed it on the roller for 24 hrs. Then I applied 60 ul/well and leave it in the hood to dry. It takes about one week but there are still some residuals at the bottom of the plate. Then I placed them in the 40-degree oven for 2 days but it still didn't work. Any suggestions would be much appreciated.