# Additively Manufactured Polymers for Electronic Components
## 5 Current Limitations and Overcoming Strategies  
Three-dimensional-printed polymers have been used in a vast variety of electronic applications. ICPs are mostly utilised to make thin-film transistors and OLEDs. The main advantage of using these kinds of materials over more traditional ones is their flexibility, which enables, for instance, their use in electronic skins and wearable devices. The main challenge is the durability and electrical conductivity under bending. Indeed, many works show that electrical properties are reduced during bending or after bending cycles. Therefore, there should be a focus on how to improve the durability of the electrical performance of intrinsically conductive polymers. A solution is to add fillers to improve the mechanical properties of the material. For example, [PERSON] et al. developed a PEDOT:PSS/GO nanocomposite, which maintained its properties after 1000 cycles with a bending strain of 30% [178]. Theoretically, many fillers can be employed to achieve this goal, such as graphene, silver nanoparticles, and MXenes. The choice of the most appropriate filler depends on the desired properties and the mechanical stress to which the devices are subjected. The possibility of enhancing PEDOT:PSS properties through the addition of fillers is widely investigated in the literature. However, the same level of knowledge is not present for other ICPs, such as polyacetylene, polyaniline, and polypyrrole. Moreover, the number of studies regarding AM of ICPs other than PEDOT:PSS is limited and should be improved, taking advantage of all of the studies regarding PEDOT:PSS. In addition to mechanical stresses, the long-term reliability of additively manufactured conductive polymers requires careful evaluation under realistic operational conditions, such as thermal cycling, prolonged humidity exposure, and electrical ageing. These factors critically influence the performance of polymer-based devices, particularly in wearable \begin{table}
\begin{tabular}{c c c c c} \hline
**Application** & **Material** & **AM Technology** & **Highlights** & **Reference** \\ \hline Strain sensor & CNT nanocomposite & AJP & High mechanical durability & \\  & Graphene nanocomposites & IJP & Relatively high electrical conductivity & [54; 104; 139] \\  & PEDOT:PSS & DIW & & \\ \hline  & Silver & SL & Relatively high conductivity & \\ Sensor for human & nanocomposites & & Poor mechanical properties & [53; 142] \\ health monitoring & PEDOT:PSS & AJP & & \\ \hline  & CNT & SL & High electrical conductivity & [150; 157] \\ Actuators & Graphene nanocomposites & DIW & & \\ \hline Thin-film transistor & PEDOT:PSS & SL & High performance & \\  & & LIFT & High resolution & [92; 174] \\ \hline  & & SL & Low viscosity & \\  & PEDOT:PSS & IJP & High resolution & [165; 175; 176] \\  & & & High performance & \\ \hline OSCs & PEDOT:PSS & IJP & Freedom of design & \\  & P3 HT:PCBM & EHD & Low efficiency & [168; 169; 170] \\ \hline  & & IJP & Good resolution & \\ Wafer bonding & BCB & AJP & Ink viscosity is critical & \\  & & & Overspray for AJP & \\ \hline Packaging & SU-8 & IJP & Good printing quality & \\  & & AJP & Presence of overspray & [133; 177] \\ \hline \end{tabular}
\end{table} 
Table 2: Summary of the most used applications for 3D printing of polymers in electronics. electronics, embedded sensors, and soft robotics, where environmental fluctuations are unavoidable. Thermal cycling, for example, induces differential expansion and contraction in multilayer systems, potentially leading to delamination as envisaged by [PERSON] et al. [179]. Similarly, humidity exposure is especially critical for materials like PEDOT:PSS, resulting in a progressive decrease in conductivity above 70% relative humidity [180]. Despite extensive research on bending-induced conductivity loss, few studies have systematically quantified these other degradation pathways in printed systems. A recent investigation, for instance, revealed that PEDOT:PSS films can still show a decrease in conductivity under high-temperature and high-humidity conditions [181].