Influence of optical penetration depth on actuated shape of liquid crystal network sheets

• A large-deflection model of LCN sheets integrating photochemical reaction nonlinear dynamics is formulated. • An effective numerical method is proposed to simulate temporal photomechanical response evolution. • Novel light-intensity-regulated shape transitions of LCN sheets are demonstrated via two typical examples. The photomechanical deformation of azobenzene-containing liquid crystal network sheets has attracted wide research interest due to their diverse potential applications. Most existing theoretical models assume exponential light intensity decay along the sheet thickness, confining predicted photo-induced strain to a shallow subsurface region. To address this limitation, this study develops a large-deflection photomechanical model and corresponding numerical method for such sheets, based on the nonlinear dynamics of photo-isomerization and absorption, to systematically explore light penetration depth variation under different incident intensities and its regulatory effect on deformation. Two typical cases are designed, with the director orientation varying either along the thickness or in-plane direction. Simulations and analyses show that incident light intensity variations alter light penetration depth, triggering a transition in the sheet’s spontaneous deformation mode and significantly distinct configurations. These results offer new insights for designing and applying liquid crystal network shape-morphing structures.