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Abstract A key challenge in bioelectronics is to establish and improve the interface between electronic devices and living tissues, enabling a direct assessment of biological systems. Sensors integrated with plant tissue can provide valuable information about the plant itself as well as the surrounding environment, including air and soil quality. An obstacle in developing interfaces to plant tissue is mitigating the formation of fibrotic tissues, which can hinder continuous and accurate sensor operation over extended timeframes. Electronic systems that utilize suitable biocompatible materials alongside appropriate fabrication techniques to establish plant-electronic interfaces could provide for enhanced environmental understanding and ecosystem management capabilities. To meet these demands, this study introduces an approach for integrating printed electronic materials with biocompatible cryogels, resulting in stable implantable hydrogel-based bioelectronic devices capable of long-term operation within plant tissue. These inkjet-printed cryogels can be customized to provide various electronic functionalities, including electrodes and organic electrochemical transistors (OECTs), that exhibit high electrical conductivity for embedded conducting polymer traces (up to 350 S/cm), transconductance for OECTs in the mS range, a capacitance of up to 4.2 mF g⁻¹in suitable structures, high stretchability (up to 330% strain), and self-healing properties. The biocompatible functionalized cryogel-based electrodes and transistors were successfully implanted in plant tissue, and ionic activity in tomato plant stems was collected for over two months with minimal scar tissue formation, making these cryogel-based printed electronic devices excellent candidates for continuous, in-situ monitoring of plant and environmental status and health. 

Abstract The chemical composition of growing media is a key factor for plant growth, impacting agricultural yield and sustainability. However, there is a lack of affordable chemical sensors for ubiquitous nutrient ion monitoring in agricultural applications. This work investigates using fully printed ion‐sensor arrays to measure the concentrations of nitrate, ammonium, and potassium in mixed‐electrolyte media. Ion sensor arrays composed of nitrate, ammonium, and potassium ion‐selective electrodes and a printed silver‐silver chloride (Ag/AgCl) reference electrode are fabricated and characterized in aqueous solutions in a range of concentrations that encompass what is typical for agricultural growing media (0.01 mm–1m). The sensors are also tested in mixed‐electrolyte solutions of NaNO₃, NH₄Cl, and KCl of varying concentrations, and the recorded potentials are input into Nernstian and artificial neural network models to compare the prediction accuracy of the models against ground truth. The artificial neural network models demonstrated higher accuracy over the Nernstian model, and the model using only ion‐sensor inputs is 7.5% more accurate than the Nernstian model under the same conditions. By enabling more precise and efficient fertilizer application, these sensor arrays coupled to computational models can help increase crop yields, optimize resource use, and reduce environmental impact. 

Abstract 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.