Mechanical forces regulate many cell functions such as differentiation and proliferation. Existing traction force methodology is often limited to measurements in the two-dimensional plane. Recent...Show moreMechanical forces regulate many cell functions such as differentiation and proliferation. Existing traction force methodology is often limited to measurements in the two-dimensional plane. Recent studies have used hydrogel micro-particles to measure cell forces in a complex 3D environment such as a spheroid. However, these micro-particles have not been fully characterised. We show here the synthesis of hydrogel micro particles with size and stiffness similar to cells. We also show that the measured effective Young’s modulus is dependent on the size of the particle measured. The softest beads with a Young’s modulus of 175 Pa can measure normal stresses down to ~ 7.3 Pa. The synthesised beads can be used to determine cell forces in tissues such a tumour spheroids or can be used to mimic cells in tissue layers.Show less