The structure of tumors can be recapitulated as an elastic frame formed by the connected cytoskeletons of the cells invaded by interstitial and intracellular fluids. The low-frequency mechanics of this poroelastic system, dictated by the elastic skeleton only, control tumor growth, penetration of therapeutic agents, and invasiveness. The high-frequency mechanical properties containing the additional contribution of the internal fluids have also been posited to participate in tumor progression and drug resistance, but they remain largely unexplored. Here we use Brillouin light scattering to produce label-free images of tumor microtissues based on the high-frequency viscoelastic modulus as a contrast mechanism. In this regime, we demonstrate that the modulus discriminates between tissues with altered tumorigenic properties. Our micrometric maps also reveal that the modulus is heterogeneously altered across the tissue by drug therapy, revealing a lag of efficacy in the core of the tumor. Exploiting high-frequency poromechanics should advance present theories based on viscoelasticity and lead to integrated descriptions of tumor response to drugs.

Machines enabled the Industrial Revolution and are central to modern technological progress: A machine’s parts transmit forces, motion, and energy to one another in a predetermined manner. Today’s engineering frontier, building artificial micromachines that emulate the biological machinery of living organisms, requires faithful assembly and energy consumption at the microscale. Here, we demonstrate the programmable assembly of active particles into autonomous metamachines using optical templates. Metamachines, or machines made of machines, are stable, mobile and autonomous architectures, whose dynamics stems from the geometry. We use the interplay between anisotropic force generation of the active colloids with the control of their orientation by local geometry. This allows autonomous reprogramming of active particles of the metamachines to achieve multiple functions. It permits the modular assembly of metamachines by fusion, reconfiguration of metamachines and, we anticipate, a shift in focus of self-assembly towards active matter and reprogrammable materials.