e14010 Background: The key driver for effective immune cell therapies is the overall binding strength of the immune cell and the target cell (e.g. tumor cells). The overall strength is known as ‘avidity’, a parameter reflecting interaction efficiency. The key to success for immune cell therapies is generating effective and long-lasting immune responses. The avidity of an immune cell to its target is predicative of its function, but current techniques to measure avidity are low-throughput and ineffective. Herein, we describe the use of acoustic forces to discriminate immune cells based on their avidity to tumor cells. The force required to separate a cell from its target is called the ‘rupture force’, and in this study, we were able to identify the rupture forces of tumor specific and non-specific T cells and enrich these different populations for downstream characterization. Methods: T cells from a healthy donor were transduced with either a non-relevant, or a melanoma recognizing T cell receptor and selected with puromycin resistance. Melanoma cells were seeded in the flow cell and allowed to adhere overnight to form a monolayer. For confocal experiments CFSE and Cell Trace far red stained T cells were mixed in a 1:1 ratio before co-culturing them in the flow cell. An acoustic force ramp was applied within the flow cell and cell detachment was monitored. Results: T cells engineered with a melanoma antigen-recognizing T-cell receptor needed 6 times more force than non-specific T cells to be separated from the melanoma target cells. Furthermore, 1.4 to 3.6-fold enrichment of high-avidity T cells was obtained from a mixed population of specific and non-specific T cells using acoustic forces. Conclusions: These findings indicate that melanoma-specific T cells bind with a higher avidity than non-specific T cells and that they can be separated with this approach. In conclusion, we demonstrate a novel method to measure cell avidity and sort cells by utilizing acoustic forces.