Methods for Mechanical Filtration and Automated Droplet Monitoring in Electrowetting on Dielectric Devices

Discrete flow microfluidic devices have been identified as a technology that can be used to efficiently deliver health care services by reducing the cycle times and reagent consumption of common biological protocols and medical diagnostic procedures while reducing overhead costs by performing these applications at the point of care. Electrowetting on dielectric is one promising discrete flow microfluidic platform that can individually create, manipulate, and mix droplets through the application of asymmetric electric fields. The work presented outlines fundamental and practical contributions to the understanding and advancement of electrowetting on dielectric devices that the authors are using to develop a device capable of performing immunoassays on chip. Explicit analytical models for capillary force and the reduction in that force by contact angle hysteresis as a function of the three-dimensional shape of the droplet were derived to develop an empirically validated analytical model for transient motion of droplets in electrowetting on dielectric devices. This model accurately predicts the maximum droplet displacement and travel time to within 2.3% and 2.7%, respectively; whereas the average droplet velocity was always predicted to within 8.1%. It also demonstrates a method for real time monitoring of droplet composition, particle concentration, and chemical reactions in electrowetting on dielectric devices without optical access. This method has been used to determine the concentration of water-methanol solutions, measure the concentration of glass microspheres at various concentrations, and detect the chemical reactions that are typically used in immunoassays. A method for the mechanical filtration of droplets in these devices will also be presented. The proposed filtration method was successful at pore sizes at least two orders of magnitude below the droplet height, which is small enough to separate red and white blood cells in continuous flow microfluidic devices.

Download Full-text

Biocompatible/Biodegradable Electrowetting on Dielectric Microfluidic Chips with Fluorinated CTA/PLGA

Materials ◽

10.3390/ma11081332 ◽

2018 ◽

Vol 11 (8) ◽

pp. 1332 ◽

Cited By ~ 1

Author(s):

Kaidi Zhang ◽

Lei Chao ◽

Jia Zhou

Keyword(s):

Contact Angle ◽

Photoelectron Spectroscopy ◽

Contact Angle Hysteresis ◽

Cellulose Triacetate ◽

Microfluidic Chips ◽

Electrowetting On Dielectric ◽

Force Microscopy ◽

Atomic Force ◽

Dielectric Devices ◽

Contact Line Pinning

One of the major hurdles in the development of biocompatible/biodegradable EWOD (Electrowetting-on-dielectric) devices is the biocompatibility of the dielectric and hydrophobic layers. In this study, we address this problem by using reactive ion etching (RIE) to prepare a super-hydrophobic film combining fluorinated cellulose triacetate (CTA) and poly (lactic-co-glycolic acid) (PLGA). The contact angle (CA) of water droplets on the proposed material is about 160°. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) characterizations indicate that a slight increase in the surface roughness and the formation of CFx (C-F or CF2) bonds are responsible for the super-hydrophobic nature of the film. Alternating Current (AC) static electrowetting and droplet transportation experiments evidence that contact angle hysteresis and contact line pinning are greatly reduced by impregnating the CTA/PLGA film with silicon oil. Therefore, this improved film could provide a biocompatible alternative to the typical Teflon® or Cytop® films as a dielectric and hydrophobic layer.

Download Full-text

LBE for Generalized Hydrodynamics

10.1093/oso/9780199592357.003.0025 ◽

2018 ◽

Author(s):

Sauro Succi

Keyword(s):

Potential Energy ◽

Electric Fields ◽

Chemical Reactions ◽

Soft Matter ◽

Fluid Motion ◽

Life Sciences ◽

Scientific Discipline ◽

The Past ◽

Generalized Hydrodynamics ◽

Internal Forces

This chapter presents the main techniques to incorporate the effects of external and/or internal forces within the LB formalism. This is a very important task, for it permits us to access a wide body of generalized hydrodynamic applications whereby fluid motion couples to a variety of additional physical aspects, such as gravitational and electric fields, potential energy interactions, chemical reactions and many others. It should be emphasized that while hosting a broader and richer phenomenology than “plain” hydrodynamics, generalized hydrodynamics still fits the hydrodynamic picture of weak departure from suitably generalized local equilibria. This class is all but an academic curiosity; for instance, it is central to the fast-growing science of Soft Matter, a scientific discipline which has received an impressive boost in the past decades, under the drive of micro- and nanotechnological developments and major strides in biology and life sciences at large.

Download Full-text

Micropipette-Based Microfluidic Device for Monodisperse Microbubbles Generation

Micromachines ◽

10.3390/mi9080387 ◽

2018 ◽

Vol 9 (8) ◽

pp. 387

Author(s):

Carlos Toshiyuki Matsumi ◽

Wilson José da Silva ◽

Fábio Kurt Schneider ◽

Joaquim Miguel Maia ◽

Rigoberto E. M. Morales ◽

...

Keyword(s):

Electric Fields ◽

Microfluidic Device ◽

Soft Lithography ◽

Low Cost ◽

Characteristic Curve ◽

Microfluidic Devices ◽

Average Diameter ◽

Internal Diameter ◽

Medical Diagnostic ◽

Average Size

Microbubbles have various applications including their use as carrier agents for localized delivery of genes and drugs and in medical diagnostic imagery. Various techniques are used for the production of monodisperse microbubbles including the Gyratory, the coaxial electro-hydrodynamic atomization (CEHDA), the sonication methods, and the use of microfluidic devices. Some of these techniques require safety procedures during the application of intense electric fields (e.g., CEHDA) or soft lithography equipment for the production of microfluidic devices. This study presents a hybrid manufacturing process using micropipettes and 3D printing for the construction of a T-Junction microfluidic device resulting in simple and low cost generation of monodisperse microbubbles. In this work, microbubbles with an average size of 16.6 to 57.7 μm and a polydispersity index (PDI) between 0.47% and 1.06% were generated. When the device is used at higher bubble production rate, the average diameter was 42.8 μm with increased PDI of 3.13%. In addition, a second-order polynomial characteristic curve useful to estimate micropipette internal diameter necessary to generate a desired microbubble size is presented and a linear relationship between the ratio of gaseous and liquid phases flows and the ratio of microbubble and micropipette diameters (i.e., Qg/Ql and Db/Dp) was found.

Download Full-text

Microwave Assisted Synthesis of Organic Compounds and Nanomaterials

10.5772/intechopen.98224 ◽

2021 ◽

Author(s):

Anjali Jha

Keyword(s):

Green Chemistry ◽

Organic Synthesis ◽

Electric Fields ◽

Chemical Reactions ◽

Dipole Moments ◽

Electric Heating ◽

Microwave Assisted Synthesis ◽

Microwave Chemistry ◽

Microwave Assisted ◽

Promising Area

In the Conventional laboratory or industry heating technique involve Bunsen burner, heating mental/hot plates and electric heating ovens. To produce a variety of useful compounds for betterment of mankind, the Microwave Chemistry was introduced in year 1955 and finds a place in one of the Green chemistry method. In Microwave chemistry is the science of applying microwave radiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent or conducting ions in a solid. Polar solvents are heated as their component molecules are forced to rotate with the field and lose energy in collisions i.e. the dipole moments of molecules are important in order to proceed with the chemical reactions in this method. It can be termed as microwave-assisted organic synthesis (MAOS), Microwave-Enhanced Chemistry (MEC) or Microwave-organic Reaction Enhancement synthesis (MORE). Microwave-Assisted Syntheses is a promising area of modern Green Chemistry could be adopted to save the earth.

Download Full-text