Shape-shifting 3D protein microstructures with programmable directionality via quantitative nanoscale stiffness modulation

• Main Authors: Lee, Yih Hong, Ling, Xing Yi, Lee, Mian Rong, Phang, In Yee, Cui, Yan
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2015
• Subjects: DRNTU::Science::Physics
• Online Access: https://hdl.handle.net/10356/106828; http://hdl.handle.net/10220/25174; http://dx.doi.org/10.1002/smll.201401343
• Institution: Nanyang Technological University

The ability to shape-shift in response to a stimulus increases an organism's survivability in nature. Similarly, man-made dynamic and responsive “smart” microtechnology is crucial for the advancement of human technology. Here, 10–30 μm shape-changing 3D BSA protein hydrogel microstructures are fabricated with dynamic, quantitative, directional, and angle-resolved bending via two-photon photolithography. The controlled directional responsiveness is achieved by spatially controlling the cross-linking density of BSA at a nanometer lengthscale. Atomic force microscopy measurements of Young's moduli of structures indicate that increasing the laser writing distance at the z-axis from 100–500 nm decreases the modulus of the structure. Hence, through nanoscale modulation of the laser writing z-layer distance at the nanoscale, control over the cross-linking density is possible, allowing for the swelling extent of the microstructures to be quantified and controlled with high precision. This method of segmented moduli is applied within a single microstructure for the design of shape-shifting microstructures that exhibit stimulus-induced chirality, as well as for the fabrication of a free-standing 3D microtrap which is able to open and close in response to a pH change.