Leire Sanchez-Duenas

The increase in electronic waste highlights the need to develop sustainable, bio-based, and recyclable electronic systems.

During the last decades, increment of the demand of electronics and the programmed obsolescence have entailed a growth of the electronic waste. On this context, there is a need of developing new sustainable and/or recyclable electronic devices. Sustainability of new devices could be ensured by using biobased materials and avoiding those which are harmful for the environment. These new materials could be used to develop specific devices, as resistive temperature sensors deposited on flexible materials, for wearable devices. Resistive temperature sensors use their electrical resistivity variation with temperature to measure the environment temperature. The variation on the resistance of the sensor depends on the material they are composed of. On this work, resistive temperature sensors are printed by screen printing, with four different pastes: a silver based commercial paste and three carbon-based pastes, a commercial one and two sustainable developed pastes. The sensors were printed onto glass fiber substrate to ensure flexibility and infused with a resin to get a composite.

In the last decades, the demand for electronics and, therefore, electronic waste, has increased. To reduce this electronic waste and the impact of this sector on the environment, it is necessary to develop biodegradable systems using naturally produced materials with low impact on the environment or systems that can degrade in a certain period. One way to manufacture these types of systems is by using printed electronics because the inks and the substrates used are sustainable. Printed electronics involve different methods of deposition, such as screen printing or inkjet printing. Depending on the method of deposition selected, the developed inks should have different properties, such as viscosity or solid content. To produce sustainable inks, it is necessary to ensure that most of the materials used in the formulation are biobased, biodegradable, or not considered critical raw materials. In this review, different inks for inkjet printing or screen printing that are considered sustainable, and the materials that can be used to formulate them, are collected. Printed electronics need inks with different functionalities, which can be mainly classified into three groups: conductive, dielectric, or piezoelectric inks. Materials need to be selected depending on the ink’s final purpose. For example, functional materials such as carbon or biobased silver should be used to secure the conductivity of an ink, a material with dielectric properties could be used to develop a dielectric ink, or materials that present piezoelectric properties could be mixed with different binders to develop a piezoelectric ink. A good combination of all the components selected must be achieved to ensure the proper features of each ink.