NOVELTY - Preparing hyaluronic acid film involves soaking chip in piranha solution. The obtained chip is washed with deionized water until chip surface gets cleaned. The cleaned chip is dried by nitrogen. The obtained chip is soaked in biotinylated bovine serum albumin (bBSA) solution and then rinsed with deionized water to remove unbound bBSA molecules from chip surface. The obtained chip is dried by nitrogen. The chip is Neutravidin (RTM: modified avidin derivative) solution to obtain Neutravidin-bBSA layer on chip surface. The obtained chip is washed with deionized water.    USE - Method for preparing hyaluronic acid film used for in vitro screening of tumor cells (claimed).    ADVANTAGE - The method enables to prepare eco-friendly and non-toxic hyaluronic acid film that has good salt tolerance.    DETAILED DESCRIPTION - Preparing hyaluronic acid film involves soaking chip in piranha solution. The obtained chip is washed with deionized water until chip surface gets cleaned. The cleaned chip is dried by nitrogen. The obtained chip is soaked in biotinylated bovine serum albumin (bBSA) solution and then rinsed with deionized water to remove unbound bBSA molecules from chip surface. The obtained chip is dried by nitrogen. The chip is Neutravidin (RTM: modified avidin derivative) solution to obtain Neutravidin-bBSA layer on chip surface. The obtained chip is washed with deionized water to remove unbound Neutravidin-bBSA molecules and then dried by nitrogen. The obtained chip is immersed in biotin-Hyaluronan (HA) solution to obtain biotin-HA bound Neutravidin layer on chip surface. The obtained chip is rinsed with deionized water to remove unbound biotin-HA bound Neutravidin molecules and dried by nitrogen to obtain hyaluronic acid film. An INDEPENDENT CLAIM is included for a method for detecting CD44 binding strength, which involves:    (A) placing hyaluronic acid film into quartz crystal microbalance analyzer in phosphate buffered saline (PBS) to measure fundamental frequency, where frequency value is stable at 0.25 mu M CD44 solution and has 50 mu l/ml flow rate;    (B) incubating in PBS for half an hour;    (C) washing to remove unbound CD44; and    (D) observing binding strength of HA with CD44, if binding is strong then CD44 is not washed out with PBS and if binding is weak then 44 is washed out with PBS.