Research projects supported by

  • National Science Foundation (NSF), USA
  • San Diego State University (SDSU), USA
  • National Research Foundation (NRF), Singapore
  • National Medical Research Council (NMRC), Singapore
  • Ministry of Education (MOE), Singapore
  • National University of Singapore (NUS), Singapore
  • Advanced Research Projects Agency – Energy (ARPA-E), USA
  • National Aeronautics and Space Administration (NASA), USA
  • Rockwell Automation, USA
  • Teledyne Scientific Company, USA

Current and past research projects:

1. Electrowetting-driven solar indoor lighting (e-SIL): an optofluidic approach towards sustainable buildings 

Rooftop sunlight is collected by a solar collector and guided to individual rooms along an optical fiber (waveguide) on the bottom of which tunable liquid prisms are linearly integrated. (a) At the light-off mode, electrowetting controls the prism angle to be φ = 0°. Incoming sunlight undergoes total internal reflection and thus keeps propagating along the optical fiber without leaking to the prism bottom for indoor lighting. (b) 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 indoor illumination (Lab on a Chip, 18, 1725-1735, 2018).

2. An optofluidic solar energy collection system

A basic prism module is stacked up and expanded to achieve an arrayed prism panel, which enables  solar tracking as wide as ±80° and solar concentration as high as 2032x without any mechanical moving components. This optofluidic solar energy collector can be potentially useful for various solar power technologies such as solar thermal heating, solar indoor lighting, concentrated photovoltaic (CPV), concentrated solar power (CSP), and solar thermo-chemical reactions (Applied Energy, 162, 450, 2016).

3. Light-driven 3D droplet manipulation on flexible optoelectrowetting (OEW) devices 

This light-driven platform can be simply fabricated on a flexible photoconductive surface using a spin-coating method. A flexible OEW technology offers the benefits of device simplicity,  flexibility, and functionality over conventional electrowetting and optoelectrowetting devices (Lab on a Chip, 16, 1831, 2016).

4. Smartphone integrated optoelectrowetting (SiOEW) device for on-chip water quality sensing

With the increasing capabilities and ubiquity of smartphones and their associated digital cameras, high-performance display, and wireless communication, the SiOEW device offers a fully-integrated portable platform capable of on-chip water sample preparation and microscopic detection of the target cells , which significantly reduce the sample preparation and detection time and the labor cost by allowing timely and distributed detection of water quality. A commercially available smartphone is used as a low-intensity portable light source to perform optoelectrowetting-based pumpless and tubeless microfluidic operations such as droplet transportation, merging, mixing, and immobilization on a hydrophobic detection zone. Furthermore, a built-in smartphone camera allows to implement a simple and low-cost microscope system capable of 115x magnified imaging to achieve on-chip detection of target contents. A smartphone further allows the captured information (e.g. the location and the time of the target water sample detected, the number of the target cells, etc.) to be rapidly and wirelessly shared with a central host such as an environmental regulation agency for real-time monitoring of microbial water quality and further water quality management (Lab on a Chip, 18, 532, 2018).

5. A high-capacitance ion gel dielectric for energy applications

An ion gel offers a 2 to 3 order higher specific capacitance (c ≈ 10 μF/cm2) than that of conventional dielectrics such as SiO2 and Al2O3, while being fabricated through a simple low-cost spin- or dip-coating process. Such an extremely high capacitance results from the nanometer-thick electric double layer (EDL) capacitor formed by the compact accumulation of free counter-ions at the interface under an applied electric field. Thus, the capacitance of the ion gel layer is thickness-independent (Langmuir, 31, 8512, 2015).

6. High-performance beam steering using an electrowetting-driven liquid prism

Four prism sidewalls are assembled and dip-coated with a dielectric (ion gel) and a hydrophobic layer. An electrowetting effect controls the prism angle φ by applying bias voltages to the left and right sidewalls, separately. Due to the refractive index difference (nair ≠ n1 ≠ n2) of each medium, incoming light can be effectively steered without any bulky mechanical moving components (Applied Physics Letters, 108, 191601, 2016).

7. An optofluidic tunable Fresnel lens for 3D focal control

(a) A Fresnel lens approximates the performance of a  bulk lens, while reducing the overall thickness by breaking it down into small  subsections of the prism with different angles steeper at the edges. (b) An optofluidic tunable Fresnel lens composed of arrayed liquid prisms. Each prism is individually controlled by electrowetting to replace the  subsections of a conventional Fresnel lens. Symmetric and asymmetric control of  each prism in our Fresnel lens allows 3D focal tuning both along the longitudinal (i.e. z-axis) as well as lateral (i.e. x-axis) directions (Sensors and Actuators B: Chemical, 240, 909, 2017).