Printed flexible hybrid electronics (FHE) is finding an increasing number of applications in the fields of displays, sensors, actuators and in energy harvesting and storage. The technology involves the printing of conductive and insulating patterns as well as mounting electronic devices and circuits on flexible substrate materials. Typical plastic substrates in use are, for example, non-renewable-based poly(ethylene terephthalate) (PET) or poly(imides) (PI) with high thermal and dimensional stability, solvent resistance and mechanical strength. The aim of this study was to assess whether renewable-based plastic materials can be applied on sheet-to-sheet (S2S) screen-printing of conductive silver patterns. The selected materials were biaxially oriented (BO) bio-based PET (Bio-PET BO), poly(lactic acid) (PLA BO), cellulose acetate propionate (CAP BO) and regenerated cellulose film, NatureFlex™ (Natureflex). The biaxial orientation and annealing improved the mechanical strength of Bio-PET and PLA to the same level as the reference PET (Ref-PET). All renewable-based substrates showed a transparency comparable to the Ref-PET. The printability of silver ink was good with all renewable-based substrates and printed pattern resistance on the same level as Ref-PET. The formation of the printed pattern to the cellulose-based substrates, CAP BO and Natureflex, was very good, showing 10% to 18% lower resistance compared to Ref-PET and obtained among the bio-based substrates the smallest machine and transverse direction deviation in the S2S printing process. The results will open new application possibilities for renewable-based substrates, and also potentially biodegradable solutions enabled by the regenerated cellulose film and PLA.

Flexible and hybrid electronics (FHE) are widely utilized from wearable to automotive applications. Instead of commonly used poly(ethylene terephthalate) (PET) film, bio-based and biodegradable polymer, poly(lactic acid) (PLA), is a most promising novel substrate alternative for FHE. From the point of heat curable conductive inks, the poor heat resistance and inherent brittleness are the major drawbacks of PLA. By increasing the PLA film crystallinity through orientation and annealing, its properties can be improved. Two commercial grades, standard PLA (PLA) and a high heat PLA (hhPLA), plus one stereocomplex PLA (scPLA) blend were used to compare PLA performance with different optical purities and crystallinity for printed FHE. Machine direction orientation (MDO), biaxial orientation (BO) and annealing improved the stability of the laboratory and pilot scale manufactured PLA films. MDO was more effective in improving stiffness and strength while BO resulted in more ductile behaviour. In hhPLA the crystallinity increased from 0% to 50% improving tensile strength by 83%, tensile modulus by 52% and strain at break from 3.7% to 114% with 3 × 3 BO and annealing. The scPLA blend contained homo- and stereocomplex crystallites and a double melting peak behaviour provided higher temperature stability through final melting at 220°C. Its optical transparency reached 95%, remaining high up to 250 nm wavelength. In roll-to-roll printing, the PLA and hhPLA films were dried at 100°C prior the printing and this decreased the MD elongation from 2.55% and 0.27% to 0.00–0.05%. The sheet resistance of printed silver was <40 mΩ/sq with additional drying for printed and hybrid integrated light-emitting diode (LED) foils. Printed LED foils on PLA had dimensional and electrical performance comparable to PET, even though lower drying temperatures were used.

Depleting fossil resources and plastic pollution have generated an increasing demand for development of renewable and biodegradable polymers. Among other applications, packaging films are at the forefront of the scene. Poly(butylene succinate-co-adipate) (PBSA) is an interesting biopolymer due to its flexibility and good processability. However, its poor barrier properties limit the range of applications. On the contrary, poly(hydroxybutyrate) (PHB) biopolymer reveals good barrier performance, as well as stiffness and fast biodegradation rate. However, PHB drawbacks are its brittleness and difficult processability. By physical blending approach, a solution was delivered to overcome the shortcomings of these biopolymers, resulting in tailored properties of the films. PHB improved barrier performance of the blend film while flexible PBSA contributed to easier processability and better ductility. In this study, biobased and biodegradable blend films were produced in pilot-scale. The effects of PBSA/PHB blending were extensively studied by tensile testing, water and oxygen barrier testing, and thermal analysis. PBSA/PHB blend films exhibited improved Young’s modulus in comparison to neat PBSA. With 50 wt% PHB content, modulus of blend film was increased by 554% compared to pure PBSA film. The ductility of blend films decreased as a function of PHB content, becoming completely brittle at 50 wt%. It was found that barrier properties of PBSA/PHB films improved in comparison to neat PBSA. Oxygen transmission test results showed that oxygen permeability decreased as a function of PHB content. Similar trend was observed with water vapour permeation properties.

In an effort to move towards a more sustainable future, bioplastics are being promoted as sustainable alternatives to plastics. Nevertheless, the market transit