Khodadad Varahramyan

Nonwoven electrowetting textiles

Electrowetting of two nonwoven textile platforms is reported. Demonstrated nonwoven textiles include a polyethylene naphthalate film that was laser milled with ∼125μm pores, and pressed paper that was made using wood microfibers of 35–50μm diameter. Vacuum deposition provided an Al electrode on the polymer textile whereas layer-by-layer nanoassembly provided an organic PEI-PEDOT:PSS electrode on the wood microfibers. Both textiles were electrically insulated with parylene C and fluoropolymer. Irreversible electrowetting of water was achieved over contact angles of ∼120° to ∼70° by applying 0–100V. Completely reversible electrowetting of water/oil was also demonstrated.

Nanomanufacturing by layer-by-layer assembly - from nanoscale coating to device applications

Layer-by-layer (LbL) assembly is emerging as a key nanomanufacturing technique that is finding a broad range of applications. It is a versatile, simple, and easy to use technique, allowing the realization of novel nanometer-scale multi-layered materials and structures that can be made to have highly desirable properties, including chemical, mechanical, electrical, magnetic, thermal, and optical. The present paper discusses the LbL assembly technique and its applications, including for nanoelectromechanical systems (NEMS) and micro-electromechanical systems (MEMS) (in combination with microfabrication), for biocompatible coating, for nanoengineered capsules, for pulp microfibre nanocoating to obtain better paper, and for polymer-based electronic devices.

Conductive paper through cellulose microfibers/carbon nanotubes composite

A layer-by-layer (LbL) nanoassembly of poly(3,4-ethylenedioxythiophene) - poly(styrenesulfonate) (PEDOT-PSS) versus carbon nanotubes on lignocellulose wood microfibers has been investigated to make conductive fibers and paper. Polycation poly(ethyleneimine) (PEI) has been used in alternate deposition with anionic conductive PEDOT-PSS and carbon nanotubes, respectively, to construct the multilayer nanofilms on wood microfibers. Using a Keithley probe measurement system, current–voltage measurements have been carried out on single fibers, after deposition of each monolayer, to study the electrical properties of the coated material. It is observed that the conductivity of the microfibers, coated with up to four alternate bilayers of PEI and PEDOT-PSS (using concentration of 3mg/ml), ranged from 1 to 10 S.cm−1. It is also observed that comparable conductivity can be achieved when the fibers were coated with alternate layers of PEI and carbon nanotubes, with only 5u2005µg/ml concentration solution. The results obtained show that using the LbL nanoassembly technique, cellulose microfibers/carbon nanotubes composite can be realized cost effectively. Moreover, using the fabricated composite nano/micro tube materials, conductive paper has been produced. In this work we have demonstrated successful scale integration from nano to micro and macroscale (nanocoating – microfibers – macropaper) in developing new paper material. Such paper can be used for electromagnetic radiation shielding and other applications. The demonstrated technique is very promising for the development of smart paper technology leading to desirable products, including paper-based displays, smart cards, and sensors.A layer-by-layer (LbL) nanoassembly of poly(3,4-ethylenedioxythiophene) - poly(styrenesulfonate) (PEDOT-PSS) versus carbon nanotubes on lignocellulose wood microfibers has been investigated to make conductive fibers and paper. Polycation poly(ethyleneimine) (PEI) has been used in alternate deposition with anionic conductive PEDOT-PSS and carbon nanotubes, respectively, to construct the multilayer nanofilms on wood microfibers. Using a Keithley probe measurement system, current–voltage measurements have been carried out on single fibers, after deposition of each monolayer, to study the electrical properties of the coated material. It is observed that the conductivity of the microfibers, coated with up to four alternate bilayers of PEI and PEDOT-PSS (using concentration of 3mg/ml), ranged from 1 to 10 S.cm−1. It is also observed that comparable conductivity can be achieved when the fibers were coated with alternate layers of PEI and carbon nanotubes, with only 5u2005µg/ml concentration solution. The results obt...