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1. Electrically tunable chiral liquid crystal lens arrays

   https://doi.org/10.1117/12.2676160  

   Perera, Kelum; Haputhantrige, Nilanthi; Himel, Md_Sakhawat Hossain; Mostafa, Md; Adaka, Alex; Lavrentovich, Oleg D; Jákli, Antal I (September 2023, Proc. SPIE 12658, Liquid Crystals XXVII)

   Khoo, Iam Choon (Ed.)

   Lenses with tunable focal lengths play important roles in nature as well as modern technologies. In recent years, the demand for electrically tunable lenses and lens arrays has grown, driven by the increasing interest in augmented and virtual reality, as well as sensing applications. In this paper, we present a novel type of electrically tunable microlens utilizing polymer-stabilized chiral ferroelectric nematic liquid crystal. The lens offers a fast response time (5ms) and the focal length can be tuned by applying an in-plane electric field. The electrically induced change in the lens shape, facilitated by the remarkable sensitivity of the chiral ferroelectric nematic to electric fields, enables the tunable focal length capability. The achieved performance of this lens represents a significant advancement compared to electrowetting-based liquid lenses and opens exciting prospects in various fields, including biomimetic optics, security printing, solar energy concentration, and AR/VR devices. 

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2. Two-dimensional Individually Addressible Electrowetting Micro-Lens Array

   https://doi.org/10.1109/IPC53466.2022.9975536  

   Gilinsky, Samuel D.; Zohrabi, Mo; Supekar, Omkar D.; Lim, Wei Yang; Bright, Victor M.; Gopinath, Juliet T. (November 2022, 2022 IEEE Photonics Conference (IPC))

   In this work we present a two-dimensional micro-scale array of individually addressable, focal length tunable, electrowetting lenses fabricated using standard microfabrication techniques. The compact, transmissive nature of these arrays opens the possibility for integration into miniature optical systems involving wavefront shaping and beam steering. 

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3. Current commercialization status of electrowetting-on-dielectric (EWOD) digital microfluidics

   https://doi.org/10.1039/d0lc00144a  

   Li, Jia; Kim, Chang-Jin “CJ” (May 2020, Lab on a Chip)

   The emergence of electrowetting-on-dielectric (EWOD) in the early 2000s made the once-obscure electrowetting phenomenon practical and led to numerous activities over the last two decades. As an eloquent microscale liquid handling technology that gave birth to digital microfluidics, EWOD has served as the basis for many commercial products over two major application areas: optical, such as liquid lenses and reflective displays, and biomedical, such as DNA library preparation and molecular diagnostics. A number of research or start-up companies ( e.g. , Phillips Research, Varioptic, Liquavista, and Advanced Liquid Logic) led the early commercialization efforts and eventually attracted major companies from various industry sectors ( e.g. , Corning, Amazon, and Illumina). Although not all of the pioneering products became an instant success, the persistent growth of liquid lenses and the recent FDA approvals of biomedical analyzers proved that EWOD is a powerful tool that deserves a wider recognition and more aggressive exploration. This review presents the history around major EWOD products that hit the market to show their winding paths to commercialization and summarizes the current state of product development to peek into the future. In providing the readers with a big picture of commercializing EWOD and digital microfluidics technology, our goal is to inspire further research exploration and new entrepreneurial adventures. 

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4. Electrically Tunable Polymer Stabilized Chiral Ferroelectric Nematic Liquid Crystal Microlenses

   https://doi.org/10.1002/adom.202302500  

   Perera, Kelum; Haputhantrige, Nilanthi; Himel, Md_Sakhawat_Hossain; Mostafa, Md; Adaka, Alex; Mann, Elizabeth_K; Lavrentovich, Oleg_D; Jákli, Antal (November 2023, Advanced Optical Materials)

   Abstract Tunable optical lenses are in great demand in modern technologies ranging from augmented and virtual reality to sensing and detection. In this work, electrically tunable microlenses based on a polymer‐stabilized chiral ferroelectric nematic liquid crystal are described. The power of the lens can be quickly (within 5 ms) varied by ≈500 diopters by ramping an in‐plane electric field from 0 to 2.5 V µm⁻¹. Importantly, within this relatively low‐amplitude field range, the lens is optically isotropic; thus, its focal length is independent of the polarization of incoming light. This remarkable performance combines the advantages of electrically tuned isotropic lenses and the field‐controlled shape of the lens, which are unique properties of chiral ferroelectric nematic liquid crystals and have no counterpart in other liquid crystals. The achieved lens performance represents a significant step forward as compared to liquid lenses controlled by electrowetting and opens new possibilities in various applications such as biomimetic optics, security printing, and solar energy concentration. 

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5. A review of optoelectrowetting (OEW): from fundamentals to lab-on-a-smartphone (LOS) applications to environmental sensors

   https://doi.org/10.1039/D2LC00372D  

   Thio, Si Kuan; Park, Sung-Yong (October 2022, Lab on a Chip)

   Electrowetting-on-dielectric (EWOD) has been extensively explored as an active-type technology for small-scale liquid handling due to its several unique advantages, including no requirement of mechanical components, low power consumption, and rapid response time. However, conventional EWOD devices are often accompanied with complex fabrication processes for patterning and wiring of 2D arrayed electrodes. Furthermore, their sandwich device configuration makes integration with other microfluidic components difficult. More recently, optoelectrowetting (OEW), a light-driven mechanism for effective droplet manipulation, has been proposed as an alternative approach to overcome these issues. By utilizing optical addressing on a photoconductive surface, OEW can dynamically control an electrowetting phenomenon without the need for complex control circuitry on a chip, while providing higher functionality and flexibility. Using commercially available spatial light modulators such as LCD displays and smartphones, millions of optical pixels are readily generated to modulate virtual electrodes for large-scale droplet manipulations in parallel on low-cost OEW devices. The benefits of the OEW mechanism have seen it being variously explored in its potential biological and biochemical applications. This review article presents the fundamentals of OEW, discusses its research progress and limitations, highlights various technological advances and innovations, and finally introduces the emergence of the OEW technology as portable smartphone-integrated environmental sensors. 

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