Roadmap on printable electronic materials for next-generation sensors

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world

Low-cost monolithic processing of large-area ultrasound transducer arrays

Large-area flexible ultrasound arrays can offer new ultrasound modalities in multiple fields. The production of these arrays when using CMOS-type fabrication techniques faces scalability challenges and costs increase dramatically when upscaled to large dimensions. We investigate the monolithic production of large-area PPT (Printed Polymer Transducer) arrays directly on a flexible substrate. Here, a vibrating membrane is defined by a circular opening in a thick photoresist layer. Since the photoresist layer is processed on top of the P(VDF-TrFE), a thin barrier layer is used to prevent diffusion into the P(VDF-TrFE). An annealing procedure is developed to reduce the surface roughness of the P(VDF-TrFE) layer and make it compatible with thin film electrode deposition. We measure a remnant polarization of 7-8 μC/cm2 and a coercive field of around 50 MV/m. Laser scanning vibrometer measurements reveal a uniform peak displacement and fundamental resonance frequency (66 kHz) across the PPT array

Low-cost monolithic processing of large-area ultrasound transducer arrays

\u3cp\u3eLarge-area flexible ultrasound arrays can offer new ultrasound modalities in multiple fields. The production of these arrays when using CMOS-type fabrication techniques faces scalability challenges and costs increase dramatically when upscaled to large dimensions. We investigate the monolithic production of large-area PPT (Printed Polymer Transducer) arrays directly on a flexible substrate. Here, a vibrating membrane is defined by a circular opening in a thick photoresist layer. Since the photoresist layer is processed on top of the P(VDF-TrFE), a thin barrier layer is used to prevent diffusion into the P(VDF-TrFE). An annealing procedure is developed to reduce the surface roughness of the P(VDF-TrFE) layer and make it compatible with thin film electrode deposition. We measure a remnant polarization of 7-8 μC/cm\u3csup\u3e2\u3c/sup\u3e and a coercive field of around 50 MV/m. Laser scanning vibrometer measurements reveal a uniform peak displacement and fundamental resonance frequency (66 kHz) across the PPT array.\u3c/p\u3

Effect of Co-Solvents on the Crystallization and Phase Distribution of Mixed-Dimensional Perovskites

Solution-processed quasi-2D perovskites are promising for stable and efficient solar cells because of their superior environmental stability compared to 3D perovskites and tunable optoelectronic properties. Changing the number of inorganic layers (n) sandwiched between the organic spacers allows for tuning of the bandgap. However, narrowing the phase distribution around a specific n-value is a challenge. In-situ UV–vis–NIR absorption spectroscopy is used to time-resolve the crystallization dynamics of quasi-2D butylammonium-based (BA) perovskites with <n> = 4, processed from N,N-dimethylformamide (DMF) in the presence of different co-solvents. By combining with photoluminescence, transient absorption, and grazing-incidence wide-angle X-ray scattering, the crystallization is correlated to the distribution of phases with different n-values. Infrared spectroscopy and density functional theory reveal that the phase distribution correlates with perovskite precursor—co-solvent interaction energies and that stronger interactions shift the phase distribution towards smaller n-values. Careful tuning of the solvent/co-solvent ratio provides a more homogeneous phase distribution, with highly oriented perovskite crystals and suppressed formation of n = 1–2 phases, providing a power conversion efficiency for BA2MA3Pb4I13 solar cells that increases from 3.5% when processed from DMF to over 11% and 10% when processed from DMF/dimethyl sulfoxide and DMF/N-methyl-2-pyrrolidone mixtures, respectively.ChemE/Opto-electronic Material