Dear Colleagues,

As an additive manufacturing process, printing is not only enabling a great freedom of design but is also a resource-efficient technology. Technical progress in functional printing and novel organic and inorganic nanomaterials have significantly advanced the field of printed electronics in the last decade. These printing technologies span different production scales. Reel-to-reel printing is applied for large-scale production of large area devices such as photovoltaic cells, sensor arrays and luminous wallpapers. Digital printing such as inkjet printing and aerosol-jet printing are examples of additive processes that allow resource efficient customized fabrication in small and medium batches. Possible applications are, e.g., wearable or even stretchable electronics, such as skin patches for monitoring of health parameters. While new nanomaterials continuously expand the application fields of functional printing, significant deficiencies remain with respect to structural resolution, switching speed of logic devices as well as reliability and long-term stability of printed devices and systems. While these aspects are in the focus of significant research efforts, to date, silicon microelectronics are still unmatched in these areas and cannot (yet) be re-placed by printed devices. Hence, in many cases, printed devices and systems are combined with silicon microelectronics. This way, the best of both worlds is created—hybrid printed electronics.

A frequently used functionality of printed electronics is flexibility or bendability using foil substrates. A common approach to connect these foil substrates with printed devices to a PCB is to print a contact array that matches with a FPC connector. Another approach is to mount silicon devices onto a foil substrate. If a fully flexible electronic circuit is desired, thinned bare dies are mounted as flip-chips. This approach poses significant challenges for the interconnection of materials and processes, since foil substrates and printed traces are often less chemically and thermally robust than their PCB counterparts. Moreover, packaging materials and processes have to be identified that protect the mounted chips without compromising flexibility. In addition to these types of flexible or bendable hybrid printed electronics, there are other, less explored classes, where printing processes and novel nanomaterials bring added functional benefits to microelectronics. The range of inks based on novel nanomaterials is continuously expanding and holds potential for new applications. Hence, new functionalities can be realized by printing devices such as piezo sensors with these materials on a substrate. The supplementary circuitry is, therefore, realized with standard silicon and PCB-based microelectronics, thus combining the two subsystems into a different type of hybrid printed electronic. There are also examples where new functionality is not only realized by the ink, but also by substrates whose properties (e.g., capacitance) are altered by the printed structure. Another approach is to leave planar electronics and go to 3D substrates, e.g., Molded Interconnect Devices (MID) or in-mold electronics. Here, 3D substrates are injection molded, thermoformed or fabricated by additive manufacturing (AM) processes. Printing techniques are applied to generate conductive traces and devices on the sculptured surfaces. Challenges lie again in mounting pack-aged or unpackaged silicon devices. Moreover, the issues of encapsulation and reliability are even more challenging than in 2D hybrid printed electronics.

This Special Issue of Micromachines on “Hybrid printed electronics” seeks to showcase research papers and review articles focusing on all kinds of electronics composed of a combination of both, printed devices and standard silicon microelectronics, as well as the related process chains, in particular mounting techniques, packaging and reliability aspects.

Dr. Ulrich Gengenbach
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• hybrid printed electronics
• design, manufacturing, process chains
• substrates for special application requirements or with special functions
• 3D electronic substrates
• mounting techniques
• thinned chips
• interconnection materials
• yield
• reliability
• encapsulation, packaging
• applications of hybrid printed electronics