Low Haze Structures for Transparent Flexible Electrodes by Electrospinning Processes
April 17, 2017 | INMEstimated reading time: 2 minutes
Flexible, transparent, and conductive electrodes (FTCE) are a key enabling technology for the new generation of flexible, printable and wearable electronics. The touchscreens and displays of the future will be curved and flexible and integrated into cars, phones, or medical technology. Tapping and wiping can only work on flexible devices, when flexible materials are used for touchscreens and electric circuits, but not brittle materials like indium tin oxide or silicon. For this purpose, INM - Leibniz Institute for New Materials is working with the process of electrospinning, a technique that produces ultrafine fibers that are up to 100 times thinner than a human hair. These fibers are collected on glass or on foils in an unstructured, wide mesh net. When conductive materials are spun, flexible conductive transparent electrodes could be produced. These FTCEs have transparencies comparable to indium tin oxide with low haze less than two percent.
Electrospinning relies on the electro-hydrodynamics of a polymer droplet in a strong electromagnetic field. The polymer droplet deforms into a cone under the electromagnetic field and ejects a jet of liquid polymer to reduce the charge on the droplet. Once in the air the polymer jet experiences a bending stability causing the fiber to whip through the air effectively drawing the fiber to diameters below 500 nanometers. The fibers are collected on glass or on a film in an unstructured, wide mesh net. "Our innovation lies in the choise of starting materials. We can use sols, which have to be calcined, or polymers and composites with no further heat treatment. Depending on the starting material, it is possible to produce both intrinsically conductive fibers and those which are electrically conductive in a further step via photochemical metallization," explains Peter William de Oliveira, Head of the InnovationCenter INM.
In contrast to patterning processes via stamps or printing methods, electrospinning easily produces unstructured fiber networks with sufficient space between the fibers that light scattering is reduced to less than two percent. At the same time, the length of the fibers reduces both the number of fibers needed for conductivity with sufficient coverage and connections between the fibers which reduce the contact resistance. With fiber thicknesses well under 500 nanometers, the fibers are not visible to the human eye and appear transparent. The net-like, random nature of the fiber deposition also eliminates typical diffraction phenomena, such as distracting rainbow effects.
"This process is machine-compatible and therefore allows a very efficient path for the manufacture of such electrodes. At the InnovationCenter we have a spinning station with which we can meet the different needs of the interested parties," says de Oliveira. For example, electrodes could be developed for flexible displays, for photo-voltaics or for passive sensors.
The fibers produced by electrospinning could not only be used as electrodes, but are also suitable to be woven into electronics, or to use them for active water treatment because of their high surface area and material properties.
About INM
INM – Leibniz Institute for New Materials, situated in Saarbrücken, is an internationally leading centre for materials research. INM conducts research and development to create new materials – for today, tomorrow and beyond. Research at INM is performed in three fields: Nanocomposite Technology, Interface Materials, and Bio Interfaces. INM is an institute of the Leibniz Association and has about 240 employees.
Suggested Items
Material Insight: The Dielectric Constant of PCB Materials
05/17/2024 | Dr. Preeya Kuray -- Column: Material InsightIn the world of PCB design, miniaturization can be achieved by using low dielectric constant (Dk) materials. Low Dk materials can allow for a reduction in thickness while maintaining a given trace width, leading to lower transmission loss and higher density circuitry.
IPC APEX EXPO: Some Thoughts About Growth
05/16/2024 | Dan Feinberg, I-Connect007After two and a half days of wandering the aisles at IPC APEX EXPO 2024, for the first time, I almost felt like I was exploring CES. There were so many booths and exhibits that I could describe, but I’d like to focus on the growth and huge value of this event, which has expanded well beyond just the growing and impressive exhibit show floor.
The Shaughnessy Report: Unlock Your High-speed Material Constraints
05/15/2024 | Andy Shaughnessy -- Column: The Shaughnessy ReportThe world of PCB materials used to be a fairly simple one. It was divided into two groups: the “traditional” laminates, often called FR-4, and the high-speed laminates developed especially for high-speed PCBs. These were two worlds that usually didn’t collide. But then traditional laminates started getting better, and high-speed designers and design engineers took notice and started to reconsider what FR-4 could be used for.
Breaking High-speed Material Constraints: Design007 Magazine — May 2024
05/14/2024 | I-Connect007 Editorial TeamDo you need specialty materials for your high-speed designs? Maybe not. Improvements in resins mean designers of high-speed boards can sometimes use traditional laminate systems instead of high-speed materials, saving time and money while streamlining the fab process. In the May 2024 issue of Design007 Magazine, our contributors explain how to avoid overconstraining your materials when working with high-speed boards.
Indium Experts to Present at Electronics in Harsh Environments SMTA Conference
05/13/2024 | Indium Corporationndium Corporation Technical Manager for Europe, Africa, and the Middle East, Karthik Vijay, will deliver a technical presentation and Indium Corporation Senior Technologist, Dr. Ronald Lasky, will deliver both a workshop and technical presentation at the Electronics in Harsh Environments SMTA Conference on May 14-16 in Copenhagen, Denmark.