Femtosecond Laser Thermal Accumulation-Triggered Micro-/Nanostructures with Patternable and Controllable Wettability Towards Liquid Manipulating

Abstract

Versatile liquid manipulating surfaces combining patternable and controllable wettability have recently motivated considerable attention owing to their significant advantages in droplet-solid impacting behaviors, microdroplet self-removal, and liquid-liquid interface reaction applications. However, developing a facile and efficient method to fabricate these versatile surfaces remains an enormous challenge. In this paper, a strategy for the fabrication of liquid manipulating surfaces with patternable and controllable wettability on Polyimide (PI) film based on femtosecond laser thermal accumulation engineering is proposed. Because of its controllable micro-/nanostructures and chemical composition through adjusting the local thermal accumulation, the wettability of PI film can be tuned from superhydrophilicity (~ 3.6°) to superhydrophobicity (~ 151.6°). Furthermore, three diverse surfaces with patternable and heterogeneous wettability were constructed and various applications were successfully realized, including water transport, droplet arrays, and liquid wells. This work may provide a facile strategy for achieving patternable and controllable wettability efficiently and developing multifunctional liquid steering surfaces.

Keywords: Femtosecond laser; Liquid manipulating; Micro-/nanostructures; Thermal accumulation; Wettability.

Fig. 1

a Schematic diagram of the preparation of the laser-treated PI film. Maximum temperatures of treated PI film with different repetition rates and power percentages are shown on the upper right corner. b Optical photographs for pristine PI film, two types of laser-treated PI films and their surface wettability. c Various potential applications of superhydrophilic–superhydrophobic patterned surfaces

Fig. 2

SEM images of a PI, b LRLLP, and c HRHLP film surfaces. Elemental chemical composition and maps of C, N, and O for d PI, e LRLLP, and f HRHLP film surfaces. 3D morphology and cross-sectional profiles for g LRLLP, and h HRHLP film surfaces

Fig. 3

Static WCAs of a PI, b LRLLP, and c HRHLP films. Mechanism illustration of d PI, e LRLLP, and f HRHLP film surfaces wettability. Dynamic wetting behaviors of a water droplet (4 μL) on g PI, h LRLLP, and i HRHLP film surfaces. j Static WCA of the laser-treated PI film at different laser repetition rate and power. “ × ” means that the laser power cannot reach the designative value or is less than the damage threshold under the corresponding repetition rate. k WCAs of the LRLLP and HRHLP films with different laser scanning speeds. l WCAs of the LRLLP and HRHLP films placed in air for 7 days

Fig. 4

a Schematic diagram of water transport on superhydrophilic path. b Qualitative mechanism of water transport on superhydrophilic path. c A series of optical photographs for water transport along superhydrophilic path. d Infrared images of water transport along superhydrophilic path. e Schematic diagram and mechanism illustration of the constructed process for the droplet arrays. f Optical photographs for the droplet arrays. g Optical photographs for the designed superhydrophilic–superhydrophobic patterns filled with water dyed with Methylene Blue

Fig. 5

a Scheme diagram of a liquid contained in a solid vessel and inside a liquid well. b Optical photographs for the construction of a circular liquid well. Water constructed an annular water wall on the superhydrophilic areas. Oil was then added into the water wall. The inner and outer diameters of the superhydrophilic areas were 10 and 15 mm, respectively. c The self-healing properties of the liquid well using a knife to cut the liquid well. d A series of optical photographs for the liquid well with the increase in oil. e Scheme diagram for a cross section of the liquid well with different volumes of contained oil. f Maximum heights of the contained oil and height of an annular water wall as functions of water volume. All the used water and oil were dyed with Methylene Blue and Oil Red, respectively