Fig. 1. Schematic of the system and calibration of light penetration parameter.

(A) Schematic of the polymer network. The micropost is composed of a network of polymer chains. Mesogens (gray) are attached side-on to the polymer backbone (black), and the chains are cross-linked by an azobenzene derivative (green). The orientation of the nematic director is indicated by the double-headed red arrow. Under UV light, the cross-linkers undergo a trans-cis isomerization, disrupting the local nematic order. This effect attenuates deeper into the material. (B) Schematic of the post. The elastomeric micropost is modeled with a set of initially cubic finite elements, at a scale of one element per 2.5 μm. The incident light source can be varied in both the polar (θ) and azimuthal directions (ϕ). (C) Calibration of light-scattering distance. The penetration of light was assumed to fall off exponentially, with a length scale chosen to match experimental results of an 18° deflection for light incident at 30° from vertical, for a micropost of height 75 μm and width 25 μm. From this comparison, we obtain a value of 6 μm for the penetration depth. The inset shows the bending angle (δ) measured by the deflection of the surface normal at the top of the post relative to its initial vertical orientation.