4D Biofabrication: 3D Cell Patterning Using Shape‐Changing Films

Abstract

A novel approach for fabrication of 3D cellular structures using new thermosensitive shape‐changing polymer films with photolithographically patterned surface—4D biofabrication is reported. The surface of shape‐changing polymer films is patterned to selectively adsorb cells in specific regions. The 2D cell pattern is converted to the 3D cell structure after temperature‐induced folding of the polymer films. This approach has a great potential in the field of tissue engineering and bioscaffolds fabrication.

3D-to-3D Microscale Shape-Morphing from Configurable Helices with Controlled Chirality

“…As has been demonstrated, PNIPAm undergoes swelling/deswelling when exposed to temperatures below/above its lower critical soluble temperature (LCST), while the PMMA layer volume is temperature-independent . The inhomogeneous swelling properties provided an interfacial stress for driving the self-folding behaviors. , The PNIPAm/PMMA microsheets were fabricated by a one-step photo-cross-linking process by passing 254 nm UV light through a photomask, followed by washing away the un-cross-linked region (Figure a).…”

Soft Micromotors with Switchable Motion Enabled by 3D-to-3D Shape Reconfiguration

“…Here, the microsheets could be considered as elastic plates; they underwent rolling (the first-order buckling) if the cumulative stress was above a certain critical stress, according to the theory of stability of elastic plates . And the curvature of the self-rolled microsheets can be estimated by the Timoshenko equation , (see more details in Supporting Information S1.10), which is determined by the total thickness of the bilayer sheet, thickness ratio, and modulus ratio of PMMA/PNIPAm, as well as the strain difference between PNIPAm and PMMA. A large and positive value of strain difference was obtained at 0 °C; thus, a positive curvature could be obtained according to the equation, while, upon elevating the temperature to 40 °C, the strain difference was much less and had a negative value, resulting in a negative curvature.…”

“…This confinement effect led to nucleation of bubbles inside the chambers . Meanwhile, the concave surface was also favored for bubble nucleation due to the reduction in nucleation free energy . Thus, the bubbles only formed from the internal channels/gaps at the rolled-up state.…”

“…Correspondingly, the curvature and bending angle (which defined the upward rolling as positive, vice versa) were decreased with higher m value, indicating loosely rolled tubular structures (Figures a and S6). This is because a higher critical bending force is required for rolling the microsheets with a thicker passive layer according to the Timoshenko equation. , …”

“…In contrast, for the single bilayered stripes, it is preferred to roll vertically to the long axis due to the confinement of the two length sides by the neighboring PNIPAm parts. Meanwhile, whether both of the two inhomogeneities could be activated to cause the rolling, depending on the Young’s modulus of the materials, Poisson ratio, thickness, and lateral dimensions in accord with the Timoshenko equation for elastic plate deformation. , According to a previous work, here we chose the thickness of PMMA/PNIPAm as 243 ± 3 nm/781 ± 2 nm, respectively, with a m = 0.31, in which both of the in- and out-of-planar rolling were activated. The microsheets rolled perpendicular/parallel to the long axis of the stripe were determined by competition between the in- and out-of-planar biaxial stress generated.…”