  Optical force and torque provide unprecedented control on the spatial motion
of small particles. A valid scientific question, that has many practical
implications, concerns the existence of fundamental upper bounds for the
achievable force and torque exerted by a plane wave illumination with a given
intensity. Here, while studying isotropic particles, we show that different
light-matter interaction channels contribute to the exerted force and torque;
and analytically derive upper bounds for each of the contributions. Specific
examples for particles that achieve those upper bounds are provided. We study
how and to which extent different contributions can add up to result in the
maximum optical force and torque. Our insights are important for applications
ranging from molecular sorting, particle manipulation, nanorobotics up to
ambitious projects such as laser-propelled spaceships.
