The objective of the proposed research is to develop a small footprint MEMS force sensor with nano-Newton sensing capability, and ability to measure single biological cells directly. The approach to developing such a sensor has so far used a passive pillar-based design, with embedded piezoresistors in-substrate. The work started with sensor pillar dimensions of ~ 6 um diameter, 60 um height SU-8 pillars mounted on 'larger' 2um x 2um (WxL) piezoresistors that demonstrated sensitivity to Fx of 0.012% per uN force. Since then, sensor pillar and piezoresistor geometries have been scaled to improve Fx sensitivity almost tenfold to 0.14% per uN with a noise-limited resolution of ~ 80 nN. Future goals of the proposed research are (1) improving Fx resolution to better than 10 nN; (2) demonstrating biocompatibility of the developed sensor by testing with real-life cell samples.