In the last years, the development of new materials as well as advanced fabrication techniques have enabled the transformation of electronics from bulky rigid structures into unobtrusive soft systems. This gave rise to new thin-film devices realized on previously incompatible and unconventional substrates, such as temperature-sensitive polymers, rough organic materials or fabrics. Consequently, it is now possible to realize thin-film structures on active substrates which provide additional functionality. Examples include stiffness gradients to match mechanical properties, mechanical actuation to realize smart grippers and soft robots, or microfluidic channels for lab-on-chip applications. Composite or microstructured substrates can be designed to have bespoke electrical, mechanical, biological and chemical features making the substrate an active part of a system. Here, the latest developments of smart structures carrying thin-film electronics are reviewed. Whereby the focus lies on soft and flexible systems, designed to fulfill tasks, not achievable by electronics or the substrate alone. After a brief introduction and definition of the requirements and topic areas, the materials for substrates and thin-film devices are covered with an emphasis on their intrinsic properties. Next, the technologies for electronics and substrates fabrication are summarized. Then, the desired properties and design strategies of various active substrate are discussed and benchmarked against the current state-of-the-art. Finally, available demonstrations, and use cases are presented. The review concludes by mapping the available technologies to innovative applications, identifying promising underdeveloped fields of research and potential future progress.

Graphene is the most outstanding material among the new nanostructured carbonaceous species discovered and produced. Graphene’s astonishing properties (i.e., electronic conductivity, mechanical robustness, large surface area) have led to a deep change in the material science field. In this review, after a brief overview of the main characteristics of graphene and related materials, we present an extensive overview of the most recent achievements in biological uses of graphene and related materials.

Innovation in materials and technologies has promoted the fabrication of thin‐film electronics on substrates previously considered incompatible because of their chemical or mechanical properties. Indeed, conventional fabrication processes, typically based on photolithography, involve solvents and acids that might harm fragile or exotic substrates. In this context, transfer techniques define a route to overcome the issues related to the nature of the substrate by using supportive carriers in the electronics stack that mitigate or avoid any damages during the fabrication process. Here, a substrate‐free approach is presented for the transfer of ultra‐thin electronics (<150nm‐thick) where no additional layer besides the electronics one remains on the final substrate. Devices are transferred on several surfaces showing good adhesion and an average performance variation of 27%. Furthermore, a sensor bent to a radius of 15.25µm, shows variation in performance of 5%. The technique can also be sequentially repeated for the fabrication of stacked electronics, enabling the development of ultra‐thin devices, compliant on unconventional surfaces.

Transparent transistors are mainly investigated in view of their integration in displays and their employment in wearable electronics where the integration of flexible and imperceptible systems is an important requirement. Here, the fabrication and ac performance of flexible InGaZnO thin-film transistors (TFTs) and circuits are presented to evaluate their suitability for analog sensor conditioning applications. Functional oxides are employed to guarantee the transparency of the device, while their fabrication processes are suitable to directly realize electronics on a flexible polyimide substrate. The TFTs show stateof-the-art performance with a field-effect mobility μ eff = 19.39 cm 2 V −1 s −1 and functionality while bent to radii as low as 5 mm. Reliable scattering parameters measurements confirm transit frequencies as high as f t ≈ 7.84 MHz. Simultaneously, nMOS ring oscillators (ROs) show functionality at supply voltage V DD ranging from 1.75 to 12.25 V with a maximum oscillation frequency f osc = 132.9 kHz. Finally, common-source amplifiers (CSAs) exhibit the voltage gains up to 10.7 dB, the cutoff frequencies up to 10.8 kHz, and a power consumption down to 4.4 μW.

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