Modern society is striving for digital connectivity that demands information security. As an emerging technology, printed electronics is a key enabler for novel device types with free form factors, customizability, and the potential for large-area fabrication while being seamlessly integrated into our everyday environment. At present, information security is mainly based on software algorithms that use pseudo random numbers. In this regard, hardware-intrinsic security primitives, such as physical unclonable functions, are very promising to provide inherent security features comparable to biometrical data. Device-specific, random intrinsic variations are exploited to generate unique secure identifiers. Here, we introduce a hybrid physical unclonable function, combining silicon and printed electronics technologies, based on metal oxide thin film devices. Our system exploits the inherent randomness of printed materials due to surface roughness, film morphology and the resulting electrical characteristics. The security primitive provides high intrinsic variation, is non-volatile, scalable and exhibits nearly ideal uniqueness.

Functional inks enable manufacturing of flexible electronic devices by means of printing technology. Silver nanoparticle (Ag NP) ink is widely used for printing conductive components. A sintering process is required to obtain sufficient conductivity. Thermal sintering is the most commonly used method, but the heat must be carefully applied to avoid damaging low‐temperature substrates such as polymer films. In this work, two alternative sintering methods, damp heat sintering and water sintering are systematically investigated for inkjet‐printed Ag tracks on polymer substrates. Both methods allow sintering polyvinyl pyrrolidone (PVP) capped Ag NPs at 85°C. In this way, the resistance is significantly reduced to only 1.7 times that of the samples on polyimide sintered in an oven at 250°C. The microstructure of sintered Ag NPs is analyzed. Taking the states of the capping layer under different conditions into account, the explanation of the sintering mechanism of Ag NPs at low temperatures is presented. Overall, both damp heat sintering and water sintering are viable options for achieving high conductivity of printed Ag tracks. They can broaden the range of substrates available for flexible electronic device fabrication while mitigating substrate damage risks. The choice between them depends on the specific application and the substrate used.

Wearable medical devices offer a great opportunity to monitor human vital signs to improve healthcare. The use of printing technologies is a promising approach to fabricate the wearables. An encapsulation must be applied to achieve longterm stability and reliability of the printed wearables. In this paper, we discuss the encapsulation requirements of printed wearable medical devices. Different encapsulation approaches are illustrated by means of various examples. Thereby, the focus lies upon solution-processed encapsulation, including the compatible materials and printing technologies.

Printing technology and mounting technology enable the novel field of hybrid printed electronics. To establish a hybrid printed system, one challenge is that the applied mounting process meets the requirements of functional inks and substrates. One of the most common requirements is low process temperature. Many functional inks and substrates cannot withstand the high temperatures required by traditional mounting processes. In this work, a standardized interconnection and an automated bump-less flip-chip mounting process using a room temperature curing conductive adhesive are realised. With the proposed process, the conductive adhesive selected for the standardized interconnection can be dispensed uniformly, despite its increase of viscosity already during pot time. Electrical and mechanical performance of the interconnection are characterized by four terminal resistance measurement and shear test. The herein proposed automated process allows for fabrication of hybrid printed devices in larger batch sizes than manual assembly processes used beforehand and thus, more comprehensive evaluation of device parameters. This is successfully demonstrated in a first application, a novel hybrid printed security device. The room temperature mounting process eliminates any potentially damaging thermal influence on the performance of the printed circuits that might result from other assembly techniques like soldering.

Flexible printed electronics (FPE) are gaining attention due to their diverse applications, including smart packaging, medical and wearable devices. A key aspect in ensuring the longevity and functionality of FPE devices is their encapsulation, which shields them from adverse environmental factors such as humidity and oxygen. One promising approach to achieve this is solution-processed encapsulation, where fillers are added into a polymer matrix to form barrier films. In this work, glass flakes, graphene oxide, montmorillonite, and silica are investigated as possible fillers in poly(vinyl alcohol) (PVA). The barrier films are fabricated by doctor blading. To select the most effective filler type, a water vapor transmission rate (WVTR) test method based on an adapted desiccant method from the ASTM E96/E96M - 22 standard is developed. The optimal filler concentration in PVA is also determined. The fabricated barrier films are optically inspected. Moreover, the barrier effect of selected PVA/filler films is validated by resistance measurements of inkjet printed silver tracks subjected to damp heat and room storage conditions.