Polyimide Dielectric Layer on Filaments for Organic Field Effect Transistors: Choice of Solvent, Solution Composition and Dip-Coating Speed

Abstract

In today’s research, smart textiles is an established topic in both electronics and the textile fields. The concept of producing microelectronics directly on a textile substrate is not a mere idea anymore and several research institutes are working on its realisation. Microelectronics like organic field effect transistor (OFET) can be manufactured with a layered architecture. The production techniques used for this purpose can also be applied on textile substrates. Besides gate, active and contact layers, the isolating or dielectric layer is of high importance in the OFET architecture. Therefore, generating a high quality dielectric layer that is of low roughness and insulating at the same time is one of the fundamental requirements in building microelectronics on textile surfaces. To evaluate its potential, we have studied polyimide as a dielectric layer, dip-coated onto copper-coated polyester filaments. Accordingly, the copper-coated polyester filament was dip-coated from a polyimide solution with two different solvents, 1-methyl-2-pyrrolidone (NMP) and dimethylformaldehyde. A variety of dip-coating speeds, solution concentrations and solvent-solute combinations have been tested. Their effect on the quality of the layer was analysed through microscopy, leak current measurements and atomic force microscopy (AFM). Polyimide dip-coating with polyimide resin dissolved in NMP at a concentration of 15w% in combination with a dip-coating speed of 50 mm/min led to the best results in electrical insulation and roughness. By optimising the dielectric layer’s properties, the way is paved for applying the subsequent semi-conductive layer. In further research, we will be working with the organic semiconductor material TIPS-Pentacene

Flexible organic field-effect transistors-based biosensors: progress and perspectives

“…Since flexible OFETs-based sensors are always attached to skin or other curved objects, the substrates must also show excellent mechanical properties to withstand bending and twisting, and superior biocompatibility to their surrounding biological systems. The most commonly used substrates in flexible OFETs-based sensors include Polyethylene Terephthalate (PET) [ 71 ], Polyimide (PI) [ 72 ], Polyethylene naphthalate (PEN) [ 73 ], Parylene C, Polydimethylsiloxane (PDMS) [ 27 ], fiber (textiles) [ 74 ], paper [ 75 ], etc.…”

Smart Textiles and Sensorized Garments for Physiological Monitoring: A Review of Available Solutions and Techniques

“…They are also referred to as “smart textiles” to highlight the ability to accomplish functions that common clothes cannot fulfil [ 4 ] in various sectors, among which are healthcare [ 9 ] and industry [ 10 ]. Other commonly used terms include “intelligent fabrics”, “intelligent clothing”, “smart fabrics”, “wearable electronics”, and “textronics” [ 11 , 12 ].…”

Prototype of a Textronic Sensor Created with a Physical Vacuum Deposition Process for Staphylococcus aureus Detection

“…According to data from 2018, the wearable sensors market in 2016 reached around US$150 million, and it is expected to increase (Figure 1). The combination of textile substrates with electronic systems elements is possible using one of many methods including embroidery, knitting, weaving, ink-jet printing, dipcoating, electroless plating, magnetron sputtering, chemical vapor deposition, or physical vacuum deposition [17][18][19][20][21][22][23]. Depending on the used method, it is possible to produce electrically conductive structures at various stages when creating the final textile product.…”

“…Mathew et al described the possibility of using flexible, short-term disposable sensors on other polymer substrates to monitor health in real time, using physiological fluids such as saliva, sweat, and tear fluid (e.g., contact lenses for glucose monitoring) [26]. The combination of textile substrates with electronic systems elements is possible using one of many methods including embroidery, knitting, weaving, ink-jet printing, dipcoating, electroless plating, magnetron sputtering, chemical vapor deposition, or physical vacuum deposition [17][18][19][20][21][22][23]. Depending on the used method, it is possible to produce electrically conductive structures at various stages when creating the final textile product.…”