Our optical force simulation data ( Figure 3 ) based on the GLMT displays the axial and radial force distributions along the axial and radial directions with beam waists of 2 and 4 μm . When the beam waist is smaller than 2 μm ( not shown in the figure ) , the axial force changes along the axial direction from negative to positive at all longitudinal sections ( planes parallel to the beam axis ) , which forms the laser tweezers mode . 22 Working in this mode , the laser beam traps the cells around its focal point rather than guiding the cells to move along the beam axis . Because rapid relative motion between the trapped particle and the laser beam is always actively created in the laser patterning procedure , a large radial trapping range is required to provide sufficient trapping force even when the trapped particle is away from the optimal trapping region during laser beam navigation . Our laser cell micropatterning experiment , in which a cell in cell suspension was trapped and guided by the focused laser beam in the cell deposition chamber , was consistent with the simulated results . The experiment showed that the limited trapping range in the laser tweezers mode did not allow the trapped cell to follow the rapid 3D movement of the laser beam during high - speed patterning navigation in a large volume of cell culture medium with strong convectional flow . When the beam waist was as large as 4 μm , the axial optical force remains positive along the axial direction in all longitudinal sections ( Figure 3c ) , forming the pure - guidance mode . In this particular mode , the radial force was too small ( Figure 3d ) to confine the cell within the beam axis during the patterning navigation process .