Date Published: April 19, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Manjae Gil, Seongjun Moon, Jaewon Yoon, Sahar Rhamani, Jae‐Won Shin, Kyung Jin Lee, Joerg Lahann.
Anisotropically compartmentalized microparticles have attracted increasing interest in areas ranging from sensing, drug delivery, and catalysis to microactuators. Herein, a facile method is reported for the preparation of helically decorated microbuilding blocks, using a modified electrohydrodynamic cojetting method. Bicompartmental microfibers are twisted in situ, during electrojetting, resulting in helical microfibers. Subsequent cryosectioning of aligned fiber bundles provides access to helically decorated microcylinders. The unique helical structure endows the microfibers/microcylinders with several novel functions such as translational motion in response to rotating magnetic fields. Finally, microspheres with helically patterned compartments are obtained after interfacially driven shape shifting of helically decorated microcylinders.
Anisotropically compartmentalized microbuilding blocks have attained significant attention recently due to their unique interfacial features and their potential applications, which are impossible to address with isotropic microparticles.1, 2 Specific applications range from sensors,3 drug delivery vehicles,4 surfactants,2, 5 and catalysts6 to soft microactuators.7 This progress has been enabled by an arsenal of methods for the fabrication of compartmentalized microparticles have been developed, such as stop‐flow lithography by Doyle and co‐workers,8 droplet microfluidics by Weitz’s groups,9 or the PRINT method by DeSimone and co‐workers.10 Similarly, electrohydrodynamic (EHD) cojetting has been widely used for preparing multicompartmental microbuilding blocks.2, 3, 4, 5, 6, 7, 11, 12, 13
The experimental setup used for EHD cojetting has been previously reported for the fabrication of Janus (bicompartmental) microfibers.12 In order to ensure the continuity of process, different polymeric solutions comprised of poly(lactic‐co‐glycolic acid) (PLGA), 85% glycolic acid (Mw 50 000–75 000 g mol−1), dissolved in a mixture of chloroform and dimethylformamide (DMF) with certain viscosity are processed through parallel needles arranged in a side‐by‐side configuration. The electrical field was adjusted until a straight polymer jet maintaining laminar flow was maintained (typically 10–15 kV). During electrojetting, the polymer jet was twisted by a rotating counter electrode connected to an external motor.
In summary, polymeric microbuilding blocks with helical surface patterns and inner architectures were successfully prepared via EHD cojetting using an in situ twisting method. Defining features of the helical microstructures can be easily controlled by adjusting the twisting procedure. In addition, different types of additives can be introduced into helical microstructures or different surface decorations on the helical microstructures can also be achieved. Helical microcylinders have also been obtained by cryosectioning of microfiber bundles and these microcylinders can be shape shifted by external stimuli, resulting in microspheres with distinct compartmentalization and unique microstructures. These techniques can provide versatile methods for the preparation of helical microstructures and can be extended to mimic biological microcreatures.
Materials: Poly(d,l‐lactide‐co‐glycolide) (ester terminated, Mw 50 000–75 000 g mol−1) (PLGA) (Product No. is 430471‐5G), Poly [(m‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐p‐phenylenevinylene)] (MEHPV), poly [tris(2,5‐bis(hexyloxy)‐1,4‐phenylenevinylene)‐alt‐(1,3‐phenylenevinylene) (PTDPV), phosphate buffered saline (PBS), and N‐(3‐dimethylaminopropyl)‐N’‐EDC were purchased from Sigma‐Aldrich, USA. Sulfo‐NHS was purchased from Thermo‐Fisher Scientific, USA. Amine‐PEG‐Rhodamine with a molecular weight of 3400 Da was purchased from Nanocs.
The authors declare no conflict of interest.