While inkjet technology had already been rapidly implemented in graphic applications in the past, recently an increasing number of applications have been developed for structuring high-quality, functional materials. Thereby, inkjet inks are being formulated as solutions of functional polymers or molecules as well as dispersions of functional nanoparticles and pigments. Inkjet printing has proved to be a promising structuring technique in electronics and optoelectronics. Examples include inkjet structuring of conjugated polymers for OLEDs and displays and structuring of electrically conductive polymers or inorganic metal colloids for the production of circuit boards. Likewise, inkjet technology is being used not only for the production of DNA-based biochips and biosensors, but also implemented in fiber optic sensors. Technical inkjet printing offers a number of advantages over other printing and structuring methods on flexible substrates:
- Contactless technology; no contamination or mechanical damage to the substrate.
- Use of many printheads in parallel enables a high throughput.
- Simultaneous printing of various materials through several nozzles is possible.
- Highly precise control of the volume of material applied is achieved.
- Excellent control of lateral structure widths is achieved.
Aerosol-Jet printing allows the production of electronic, structural or biological structures on different substrates. Functionalized inks are either ultrasonically or pneumatically atomized and the resulting aerosol is continuously transmitted through a system of tubing to the printhead. The printhead focuses the aerosol jet using a protective gas toward the substrate surface. Because the nozzle is about 1-5 mm above the surface, this process is a contactless, direct structuring process with a high level of resolution and also permits the use of non-planar substrates. After the deposition, a thermal or chemical treatment is typically carried out to provide the desired electrical and / or mechanical properties and ensure the adhesion to the substrate. In contrast to similar structuring technologies applied in inkjet processes, the described method allows solutions and dispersions with a significantly greater viscosity range (1-2500 mPa·s) to be processed and achieves a minimum structure thickness of 10 m2. Depending on the duration of the process and materials used, it is also possible to generate different layer thicknesses or build multilayer structures by overprinting. The usable materials include a broad range of metallic conductors, organic semiconductors, resistors, ceramics, composite materials, dielectrics and biological materials. This technology can be applied in various industrial fields for:
These include varied functional structures (chemically active structures, surface modifications, organic (opto-) electronics, sensory elements or micro-optical applications). These technologies and the associated simplified process chain, , can save costs and, at the same time, shorten the time to market in comparison to the microsystems technologies usually used in these areas