Rapid Electrohydrodynamic-Driven Pattern Replication over a Large Area via Ultrahigh Voltage Pulses

In Situ Growth of Mushroom-Shaped Adhesive Structures on Flat/Curved Surfaces via Electrical Modulation

Gecko-inspired adhesives have an extraordinary impact on robotic manipulation and locomotion. However, achieving excellent adhesive performance on curved surfaces, especially undevelopable surfaces, is still challenging. This can be attributed to a considerable difference between the fabrication method and practical necessity, i.e., the adhesive structures are generally fabricated on a flat substrate whereas the manipulating surface is curved, resulting in a low adhesive strength. Here, an in-situ growth strategy is proposed to fabricate mushroom-shaped structures at micro/nano-scale via electrical modulation on flat or curved surfaces. Since the adhesive structures are directly grown on target surfaces without a transfer procedure, they exhibit a large contact area and stress uniformity at the interface, corresponding to an excellent adhesive force. A comparison between grown structures using the proposed method and those fabricated using traditional approaches suggests that the adhesive forces are identical for flat testing surfaces, while the difference can be up to 4 times for developable surfaces and even 25 times for undevelopable surfaces. The proposed adhesion strategy extends the application prospects of gecko-inspired adhesives from flat surfaces to curved ones, composed of developable and undevelopable surfaces, opening a new avenue to develop gecko-inspired adhesive-based devices and systems.

Rapid In-Plane Pattern Growth for Large-Area Inverse Replication Through Electrohydrodynamic Instability of Polymer Films

Nanopatterning driven by electrohydrodynamic (EHD) instability can aid in the resolution of the drawbacks inherent in conventional imprinting or other molding methods. This is because EHD force negates the requirement of physical contact and is easily tuned. However, its potential has not examined owing to the limited size of the pattern replica (several to tens of micrometers). Thus, this study proposes a new route for large-area patterning through high-speed evolution of EHD-driven pattern growth along the in-plane axis. Through the acceleration of the in-plane growth, while selectively controlling a specific edge growth, the pattern replica area can be extended from the micro- to centimeter scale with high fidelity. Moreover, even in the case of nonuniform contact mode, the proposed rapid in-plane growth mode facilitates uniform large-scale replication, which is not possible in conventional imprinting or other molding methods.

Electrohydrodynamic Nanopatterning: A Novel Solvent-Assisted Technique for Unconventional Substrates

Electrohydrodynamic (EHD)-driven patterning is a pioneering lithographic technique capable of replicating and modifying micro/nanostructures efficiently. However, this process is currently restricted to conventional substrates, as it necessitates a uniform and robust electric field over a large area. Consequently, the use of nontraditional substrates, such as those that are flexible, nonflat, or have high insulation, has been notably limited. In our study, we extend the applicability of EHD-driven patterning by introducing a solvent-assisted capillary peel-and-transfer method that allows the successful removal of diverse EHD-induced structures from their original substrates. Compared with the traditional route, our process boasts a success rate close to 100%. The detached structures can then be efficiently transferred to nonconventional substrates, overcoming the limitations of the traditional EHD process. Our method exhibits significant versatility, as evidenced by successful transfer of structures with engineered wettability and patterned structures composed of metals and metal oxides onto nonconventional substrates.