Contents I. Introduction
Microlens arrays (MLAs) exhibit some good optical properties, such as extremely large field-of-view angles, low aberration and distortion, high temporal resolution, and infinite depth of field, which have attracted considerable interest from researchers in recent years [1]. They can achieve beam focusing, coupling, segmentation, multi-beam interference, and reception [2]-[6], which play a key role in various scientific fields, such as micro-optics [7]-[9], optoelectronic devices [10], and medicine [11], [12]. As special microlenses, flexible MLAs have the advantages of good stretching and bending properties, and have attracted wide attention in recent years. Flexible MLAs have a larger detection angle, which allows for the detection of curved surfaces and acquisition of accurate signals. In addition, flexible MLAs have potential applications in three-dimensional (3D) microstructure fabrication. For example, 3D projection lithography and laser beam direct lithography on a curved substrate can be achieved by using a flexible MLA. Currently, there are various methods for fabricating MLAs, such as photolithography [13], dry etching [14], soft lithography [15], hot stamping [16], [17], and inkjet printing [18]. However, in most cases, it is difficult to manufacture a flexible MLA flexibly and integrally by using the aforementioned methods. For example, photolithography has high manufacturing precision but is expensive and has poor manufacturing flexibility. Furthermore, it is difficult to perform this process on a flexible substrate. While inkjet printing is inexpensive and flexible and it can also manufacture MLAs on flexible substrates, it cannot print high-viscosity liquids and easily blocks needles, which makes it difficult to print small droplets. Therefore, a more efficient method of manufacturing flexible MLAs is required.
