Colloidal molecules with directionality and controlled flexibility

Colloidal molecules are ideal model systems for mimicking real molecules as well as versatile building blocks for the bottom-up self-assembly of flexible and smart materials. Current colloidal molecules do not feature the typically restricted motion range and bond directionality of real molecules.

In this work, we create flexible colloidal molecules with an in situ controllable motion range by assembling spherical particles onto cubes functionalized with complementary surface-mobile DNA. We assemble colloidal molecules with different coordination number of spheres by varying the size ratio and find that they feature a constrained range of motion above a critical size ratio. Using simulations/calculations, we show that particle shape together with the multivalent bond creates an effective free energy landscape for the motion of the sphere on the cube surface. A change in temperature allows switching between full and constrained flexibility of these colloidal molecules in situ. These flexible colloidal molecules with temperature switchable motion range can be used to investigate the effect of directional, yet flexible bonds in studying their self-assembly and phase behavior, and may be employed as constructional units in microrobotics and novel smart materials.