Micropillar type three-axis force sensor for measurement of cellular force

This paper reports a three-axis force sensor that can measure cellular forces in real time with high sensitivity. The sensor features a photoresist micropillar fabricated on a flexible cross-shaped Si structure. The three dimensional forces acting on the micropillar can be detected from the resistance changes of three piezoresistors designed on the Si structure. Due to the flexibility of the Si beams, a sensing resolution on the order of several nN was obtained for both shear forces and normal force. Moreover, in our sensor design, the sensing beams are covered by a photoresist cap that prevents cells from attaching to the piezoresistors while it maintains the space for the beams and the micropillar to deform. We confirmed that our sensor can detect the normal and shear forces acting on the micropillar caused by an osteosarcoma cell during its detachment from the surrounding walls.