Particle chain display – an optofluidic electronic paper

Abstract

A particle-based display medium and a driving mechanism insensitive to the charge polarity of those particles, based on the transformation of particle chains, are developed for reflective electronic paper displays. Particle chains are formed by dipole-dipole interactions between polarized particles with an appropriate electric field applied across the tested display medium, i.e. the solution that regulates the light in the field of display technology, containing neutral polystyrene (PS) particles dispersed in water. Formation of the particle chains results in a large change in optical transmittance and reflectance of the display medium. The performance of the particle chain displays (PCD) was evaluated according to macroscopic (device), microscopic (particle) and optical (reflectance) points of view. A display medium (thickness 100 μm) containing colored PS particles (3 μm, 2.5% w/v) was polarized to display the fixed images of the directly driven electrodes and programmable images of arrayed (5 × 5) electrodes with electric fields (0.48 MV m(-1) and 0.09 MV m(-1), 500 kHz, respectively). The formation of particle chains under electric fields (0.2 MV m(-1) and 0.4 MV m(-1), 500 kHz) was observed in the microscopic images of a display medium (thickness 100 μm) with fluorescent PS particles (5 μm, 1%). Images recorded with a confocal microscope demonstrated the particle chains. The opacity, a common parameter serving to characterize a display medium, was derived by measuring the reflectance ratio of a black background to a white background of the display medium with varied thickness and particle concentration. The temporal response of a display medium (thickness 50 μm) with black PS particles (3 μm, 5%) was tested. When an electric field (0.6 MV m(-1), 500 kHz) was applied, the reflectance increased twice at the first data point in 0.7 s, attaining a contrast ratio of 2. Application of a voltage (20 s) yielded a contrast ratio of 10. The performance of a tested display medium, composed of simple PS particles and water and driven to form particle chains by polarization, is reported.

Digital Microfluidics for Manipulation and Analysis of a Single Cell

“…Here we focus more on the electric forces, including DEP and EWOD. The DEP force generated with a non-uniform electric field interacting with polarized, suspended particles [ 65 , 66 , 67 ] has been widely used to manipulate cells [ 39 , 63 , 68 , 69 ]. The DEP force is classified as positive DEP (pDEP) and negative DEP (nDEP) based on the polarizability of the particles or cells and the liquid.…”

Multiphase optofluidics on an electro-microfluidic platform powered by electrowetting and dielectrophoresis

“…3 Particle manipulation by dielectrophoresis on the EMF platform. 37 43,44 Formation of the particle chains results in a large variation of the optical transmittance and reflectance of the droplet. As shown in Fig.…”

“…Based on the study of particle manipulation in a moving droplet described above, a display medium associated with electronic paper was developed using a simple suspension of uncharged neutral particles in water. 44 Electronic paper is a paper-like display pursuing the goals of being reflective, flexible, bendable, portable, bistable and energy-saving. 29,30,45 The mechanisms of actuation (e.g., electrowetting 29,30 and electrophoresis 45 ) and materials (e.g., liquids and particles) found in many electronic paper displays are also commonly investigated in the field of microfluidics.…”

“…The particle suspension droplet was then developed as a low cost display medium. 44 The particle chains, formed out of the plane and parallel to the electric field lines, decrease the planar density of particles and greatly alter the transmittance and reflectance of the display medium to provide bright and dark states. Devices with electrodes of two designs, directly driven electrodes and arrayed electrodes shown in Fig.…”

Photofluidics – A New Platform for Biophotonics

“…The wideranging applicability of photofluidics is evident when one looks at some of the recent developments reported in this field which include random lasing [1], high resolution lens-free imaging [2], chip-based sensors for pressure [3] and concentration sensing [4], sustainable energy production and associated scale-up procedures [5], displays [6], water purification [7] and high sensitivity biomolecular sensing [8]. The wideranging applicability of photofluidics is evident when one looks at some of the recent developments reported in this field which include random lasing [1], high resolution lens-free imaging [2], chip-based sensors for pressure [3] and concentration sensing [4], sustainable energy production and associated scale-up procedures [5], displays [6], water purification [7] and high sensitivity biomolecular sensing [8].…”