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Lee Y, Lee CH, Park SY. An arrayed optofluidic system for three-dimensional (3D) focal control via electrowetting. OPTICS EXPRESS 2023; 31:17677-17694. [PMID: 37381495 DOI: 10.1364/oe.489508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 04/22/2023] [Indexed: 06/30/2023]
Abstract
A new lens capability for three-dimensional (3D) focal control is presented using an optofluidic system consisting of n × n arrayed liquid prisms. Each prism module contains two immiscible liquids in a rectangular cuvette. Using the electrowetting effect, the shape of the fluidic interface can be rapidly adjusted to create its straight profile with the prism's apex angle. Consequently, an incoming ray is steered at the tilted interface due to the refractive index difference between two liquids. To achieve 3D focal control, individual prisms in the arrayed system are simultaneously modulated, allowing incoming light rays to be spatially manipulated and converged on a focal point located at Pfocal (fx, fy, fz) in 3D space. Analytical studies were conducted to precisely predict the prism operation required for 3D focal control. Using three liquid prisms positioned on the x-, y-, and 45°-diagonal axes, we experimentally demonstrated 3D focal tunability of the arrayed optofluidic system, achieving focal tuning along lateral, longitudinal, and axial directions as wide as 0 ≤ fx ≤ 30 mm, 0 ≤ fy ≤ 30 mm, and 500 mm ≤ fz ≤ ∞. This focal tunability of the arrayed system allows for 3D control of the lens's focusing power, which could not be attained by solid-type optics without the use of bulky and complex mechanical moving components. This innovative lens capability for 3D focal control has potential applications in eye-movement tracking for smart displays, autofocusing of smartphone cameras, or solar tracking for smart photovoltaic systems.
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Thio SK, Park SY. A review of optoelectrowetting (OEW): from fundamentals to lab-on-a-smartphone (LOS) applications to environmental sensors. LAB ON A CHIP 2022; 22:3987-4006. [PMID: 35916120 DOI: 10.1039/d2lc00372d] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
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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Affiliation(s)
- Si Kuan Thio
- Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore
| | - Sung-Yong Park
- Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, CA, 92182, USA.
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Maji TK, J R A, Mukherjee S, Alexander R, Mondal A, Das S, Sharma RK, Chakraborty NK, Dasgupta K, Sharma AMR, Hawaldar R, Pandey M, Naik A, Majumdar K, Pal SK, Adarsh KV, Ray SK, Karmakar D. Combinatorial Large-Area MoS 2/Anatase-TiO 2 Interface: A Pathway to Emergent Optical and Optoelectronic Functionalities. ACS APPLIED MATERIALS & INTERFACES 2020; 12:44345-44359. [PMID: 32864953 DOI: 10.1021/acsami.0c13342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The interface of transition-metal dichalcogenides (TMDCs) and high-k dielectric transition-metal oxides (TMOs) had triggered umpteen discourses because of the indubitable impact of TMOs in reducing the contact resistances and restraining the Fermi-level pinning for the metal-TMDC contacts. In the present work, we focus on the unresolved tumults of large-area TMDC/TMO interfaces, grown by adopting different techniques. Here, on a pulsed laser-deposited MoS2 thin film, a layer of TiO2 is grown by atomic layer deposition (ALD) and pulsed laser deposition (PLD). These two different techniques emanate the layer of TiO2 with different crystallinities, thicknesses, and interfacial morphologies, subsequently influencing the electronic and optical properties of the interfaces. Contrasting the earlier reports of n-type doping at the exfoliated MoS2/TiO2 interfaces, the large-area MoS2/anatase-TiO2 films had realized a p-type doping of the underneath MoS2, manifesting a boost in the extent of p-type doping with increasing thickness of TiO2, as emerged from the X-ray photoelectron spectra. Density functional analysis of the MoS2/anatase-TiO2 interfaces, with pristine and interfacial defect configurations, could correlate the interdependence of doping and the terminating atomic surface of TiO2 on MoS2. The optical properties of the interface, encompassing photoluminescence, transient absorption and z-scan two-photon absorption, indicate the presence of defect-induced localized midgap levels in MoS2/TiO2 (PLD) and a relatively defect-free interface in MoS2/TiO2 (ALD), corroborating nicely with the corresponding theoretical analysis. From the investigation of optical properties, we indicate that the MoS2/TiO2 (PLD) interface may act as a promising saturable absorber, having a significant nonlinear response for the sub-band-gap excitations. Moreover, the MoS2/TiO2 (PLD) interface had exemplified better phototransport properties. A potential application of MoS2/TiO2 (PLD) is demonstrated by the fabrication of a p-type phototransistor with the ionic-gel top gate. This endeavor to analyze and perceive the MoS2/TiO2 interface establishes the prospectives of large-area interfaces in the field of optics and optoelectronics.
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Affiliation(s)
- Tuhin Kumar Maji
- Department of Chemical Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Sector III, JD Block, Kolkata 700106, India
| | - Aswin J R
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | | | - Rajath Alexander
- Advanced Carbon Materials Section, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Anirban Mondal
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Sarthak Das
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Rajendra Kumar Sharma
- Raja Rammana Centre for Advance Technology, Parmanu Nagar, Sahkar Nagar Extension, 1, CAT Rd, Rajendra Nagar, Indore, Madhya Pradesh 45201, India
| | | | - Kinshuk Dasgupta
- Advanced Carbon Materials Section, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Anjanashree M R Sharma
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Ranjit Hawaldar
- Centre for Materials for Electronics Technology, Off Pashan Road, Panchwati, Pune 411008, India
| | - Manjiri Pandey
- Accelerator Control Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Akshay Naik
- Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Kausik Majumdar
- Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Samir Kumar Pal
- Department of Chemical Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Sector III, JD Block, Kolkata 700106, India
| | - K V Adarsh
- Department of Physics, Indian Institute of Science Education and Research, Bhopal 462066, India
| | - Samit Kumar Ray
- Department of Chemical Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Sector III, JD Block, Kolkata 700106, India
- Department of Physics, IIT Kharagpur, Kharagpur, West Bengal 721302, India
| | - Debjani Karmakar
- Technical Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
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Thio SK, Jiang D, Park SY. Electrowetting-driven solar indoor lighting (e-SIL): an optofluidic approach towards sustainable buildings. LAB ON A CHIP 2018; 18:1725-1735. [PMID: 29726880 DOI: 10.1039/c8lc00319j] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Optofluidics is an emerging research field that combines the two disciplines of microfluidics and optics. By using microfluidic technologies for light control, optofluidic devices can offer several advantages over solid-type optical components, including optical-grade smoothness at the fluidic interface and a high degree of optical tunability without bulky and complex mechanical moving parts. These features have made optofluidic devices more versatile and reconfigurable to improve their optical performances. In this paper, we present a novel optofluidic sunlight manipulation technology for solar indoor lighting using the electrowetting principle. Rooftop sunlight is collected by a solar concentrator and guided to individual rooms along an optical fiber (waveguide) on the bottom of which tunable liquid prisms are linearly integrated. In the light-off mode, electrowetting controls the apex angle of the prisms to be φ = 0°. Under this condition, incoming sunlight experiences total internal reflection and thus keeps propagating along the optical fiber without leaking to the prism bottom for indoor lighting. In contrast, when liquid prisms are controlled to have the angle at φ > 0°, incoming sunlight is partially transmitted to the bottom surface of the arrayed prisms to contribute to interior illumination. Simulation studies validate that our electrowetting-driven solar indoor lighting (e-SIL) system is capable of variably tuning the lighting power from 0% to 98.6% of the input solar power by controlling the prism angle and varying the refractive index of prism materials. For experimental studies, we fabricated an array of 5 prisms filled with silicone oil and water. Using a fiber illuminator as a white light source that includes visible light with various incident angles, we have demonstrated two important lighting functions, (1) light on/off and (2) illumination power control. Lighting performance can be further enhanced by lowering the aspect ratio of the prism as well as increasing the number of prisms. The e-SIL technology based on tunable liquid prisms offers a new approach towards sustainable buildings that are able to reduce their electricity usage as well as provide a healthy and comfortable indoor environment under illumination of natural sunlight.
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Affiliation(s)
- Si Kuan Thio
- Department of Mechanical Engineering, Biomedical Institute for Global Health Research and Technology (BIGHEART), National University of Singapore (NUS), 117576, Singapore.
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