In Situ Electrohydrodynamic Jet Printing-Based Fabrication of Tunable Microlens Arrays

Abstract

Tunable microlens arrays (MLAs) with controllable focal lengths have been extensively used in optical sensors, biochips, and electronic devices. The commonly used method is electrowetting on dielectric (EWOD) that controls the contact angle of the microlens to adjust the focal length. However, the fabrication of tunable MLAs at the microscale remains a challenge because the size of MLAs is limited by the external electrodes of EWOD. In this study, a highly integrated planar annular microelectrode array was proposed to achieve an electrowetting tunable MLA. The planar microelectrode was fabricated by electrohydrodynamic jet (E-jet) printing and the liquid microlens was then deposited in situ on the microelectrode. This method could realize 36 tunable liquid microlenses with an average diameter of 24 μm in a 320 × 320 μm 2 plane. The fabricated tunable MLAs with higher integration levels and smaller sizes can be beneficial for cell imaging, optofluidic systems, and microfluidic chips.

Tunable and Dynamic Optofluidic Microlens Arrays Based on Droplets

“…Also, liquid microlenses can be reshaped through various external stimuli. For example, electrowetting on dielectric (EWOD) has been widely applied to change the contact angle of individual microlens to adjust the focal length of the MLAs. − Besides, another strategy based on the surface modification of substrate to change liquid contact angles and microlens’ focal length is also reported . Although these methods can achieve tunable liquid MLAs, the liquids are limited to conductive and photosensitive materials, and the tuning process is also complicated and time-consuming.…”

Microfluidic Fabrication of a PDMS Microlens for Imaging Tunability

“…In recent years, interest has grown in the fabrication of tunable microlenses and MLA as a result of their attractive merits such as being small and lightweight, enabling image magnification extinction for optical switching, and having a field of view for multiple imaging. − Therefore, microlenses and MLA have enabled great progress and applications in the focal plane optical concentration, optical efficiency enhancements, color separation, beam-shaping spatial-light-modulating systems, , optical fiber coupling, and miniature optical scanning . Comparatively speaking, for conventional optical equipment, their focal lengths are generally realized by adjusting the relative position of optical elements and mechanical parts such as gears, motors, and shutters. − Thus, conventional optical equipment is bulky and heavy and has a slow response.…”

Artificial Hyper Compound Eyes Enable Variable-Focus Imaging on both Curved and Flat Surfaces

“…Most of the application scenarios for the ACE are related to imaging and sensing, and these functions attract much attention of researchers. Unlike mammalian eyes, arthropod compound eyes consisting of the crystal vertebra, visual rod, etc., lack zooming functions and thereby have difficulty in detecting objects at different distances. , In order to achieve the zoom function of the ACE, researchers have devoted great efforts. − To endow the ACE with the zoom function, researchers commonly employed various drive forces, e.g., electromagnetic force, photothermal actuation, and pressure etc. − However, the existence of the power source increases the complexity of manufacturing and restricts applicable environments. − Additionally, this power source enables the ACE variable-focus imaging on the curved surface, and the lack of planar imaging function makes it difficult to clearly observe planar objects due to defocusing. Ommatidia have same focal lengths, and they are distributed on the curved substrate, which decides their curved imaging characteristics.…”

“…Unlike mammalian eyes, arthropod compound eyes consisting of the crystal vertebra, visual rod, etc., lack zooming functions and thereby have difficulty in detecting objects at different distances. 14,15 In order to achieve the zoom function of the ACE, researchers have devoted great efforts. 16−21 To endow the ACE with the zoom function, researchers commonly employed various drive forces, e.g., electromagnetic force, photothermal actuation, and pressure etc.…”