Generation of micropatterns of conducting polymers and aluminum using an intermediate-layer lithography approach and some applications

Abstract

Conducting polymers, because of their promising potential to replace silicon and metals in building devices, have attracted great attention since the discovery of high conductivity in doped polyacetylene in 1977. Lithographic techniques present significant technical challenges when working with conducting polymers. Sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature, and chemical solutions) makes current photolithographic methods unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in those methods. Existing non-photolithographic approaches have limitations in throughput, resolution, or electrical insulation. Therefore, an intermediate-layer lithography (ILL) approach has been recently developed by my group to produce conducting polymer micro/nanostructures. In the ILL method, an intermediate layer of an electrically insulating polymer is coated between the substrate and a layer of the conducting polymer to be printed. Subsequently, the conducting polymer is printed through mold insertion using a hot-embossing process. The current hotembossing based methods face the obstacles of residual layer and depth of field (i.e., the height variation in the mold structures). In contrast, the ILL approach does not leave a residual layer in the material of interest, making conducting polymer patterns isolated from one another and avoiding the shorting problem in the electrical applications of these patterns. Furthermore, in the ILL, the height variation potentially existing among the mold structures has been transferred to the intermediate layer, ensuring that all patterns in the mold have been properly transferred to the conducting polymer layer. In addition to conducting polymers, the ILL can also be applied to pattern metals as well as other types of polymers. This paper gives a review of this ILL method and reports the results that we have achieved to date, including generation and applications of single and multiple layers of microstructures of conducting polymers and aluminum.

Synthesis and optimization of PEDOT:PSS based ink for printing nanoarrays using Dip-Pen Nanolithography

“…Twelve pen tip-arrays (Type M, A-frame cantilevers with spring constant of 0.6 N m -1 , made of Si 3 N 4 , 107 µm in length and 22 µm in width) were used for printing and silicon inkwell arrays were used for inking. Silicon substrates were also obtained from Nanoink Inc. Gold surfaces were prepared on silicon by 10 evaporation of 4 nm thick layer of chromium and 16 nm layer of gold. The substrates before printing were rinsed with ultrapure water.…”

“…For each experiment, the multi-pen tips 5 were dipped into inkwells and then initial contact made with the surface prior to patterning to remove excess ink from the tip. After this initial "bleeding" step, it was possible to stably pattern dots across all 12 pens for well in excess of over an hour, which amounted to 40 µm dot arrays (comprising 9x9 dots) being able 10 to cover an approximate surface area of 2 x 2 mm (each pen is separated by ~60 µm). Fig.…”

“…Top-down lithography approaches can be used to fabricate precise, high resolution nano-patterned structures from electrochemically prepared macro-sized films; however the use of 55 "single-material" films limits the composition diversity of the patterned structures and areas. Lithography methods have been extensively used for patterning of CPs 10 and especially microcontact printing that can offer versatile, low-cost, surface patterning and submicron accuracy. 11 For microcontact printing, 60 an elastomeric stamp is covered with ink and placed in contact against a substrate and in one step it is possible to print a whole series of patterns.…”

Fully-Polymeric pH Sensor Realized by Means of a Single-Step Soft Embossing Technique

“…An interesting approach is to use hot embossing to transfer a desired pattern on a thin PEDOT film spin-coated on a sacrificial thermoplastic polymer layer. This technique is called intermediate layer lithography [ 23 ] and has several advantages. It has been demonstrated by Kafka et al [ 24 ] that it is possible to fabricate in a single hot embossing step both microfluidic and electrode functionalities, improving the fabrication throughput and reducing the problem of alignment.…”

High throughput soft embossing process for micro-patterning of PEDOT thin films

“…To resolve this issue, plasticizers, such as Glycerol, have been added to increase the chain mobility (lowering viscosity) [12]but they produce instability in the imprinted dimensions due to evaporation [13]. A different approach is to use intermediate layer lithography (IIL) [14] in which an intermediate layer of thermoplastic polymer is used as a substrate for the conductive layer. In this way, the conductive polymer can be printed via hot embossing and, eventually, multiple structures (such as microchannels and electrodes) can be imprinted simultaneously in one single step [15].…”