The Internet of Things (IoT) is gaining more and more popularity and it is establishing itself in all areas, from industry to everyday life. Given its pervasiveness and considering the problems that afflict today’s world, that must be carefully monitored and addressed to guarantee a future for the new generations, the sustainability of technological solutions must be a focal point in the activities of researchers in the field. Many of these solutions are based on flexible, printed or wearable electronics. The choice of materials therefore becomes fundamental, just as it is crucial to provide the necessary power supply in a green way.
1. Introduction
The term sustainability has now become commonly used, it is of great importance and is also used in different contexts. It was used for the first time in 1992, during the first UN Conference on the environment. The definition of sustainability that has been given is this:
Condition of a development model capable of ensuring the satisfaction of the needs of the present generation without compromising the possibility of future generations to realize their own [1]. This definition is centered not only on the economy and society, but above all on ecology. Sustainability and sustainable development are linked to a new idea of well-being that takes into account people’s quality of life. Environmental sustainability requires responsibility in the use of resources. It is therefore a development model to which everyone can and must contribute, starting from the awareness that every action performed by each of us has a deep impact on the environment.
Based on these considerations, the world of electronics, which for decades has been increasingly pervasive in all sectors of life (industry, medical, automation, automotive, military, consumption), cannot fail to pay maximum attention to the issue of sustainability. The electronics as fuel of the Internet of Things technology is surely leading us in a new way of conducting our lives and cities
[2], also allowing the optimization of the production processes of companies and industries and the management of services and infrastructures, limiting the consumption of resources and pollution. Management of public lighting
[3][4][5][6][7], air quality
[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] and noise pollution monitoring
[23][24][25][26][27][28][29], smart home
[30][31][32][33][34][35][36][37][38][39][40][41][42][43], smart roads, smart cars, urban mobility and transport
[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63], food and agriculture
[64][65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83], smart factories
[84][85][86][87][88][89][90][91] and medicine
[92][93][94][95][96][97][98][99][100][101][102] are examples of the great potentialities of the IoT. However, the increase in connectivity inevitably translates into an increase in electronic devices and systems (sensors, data acquisition and processing systems, communication systems) and therefore the problem of respecting the environment, both in the production step and disposal of disused systems is, nowadays, of fundamental importance also in the field of the IoT industry. Thanks to the availability of eco-compatible materials, flexible electronics, which is a solution that is increasingly gaining space in many applications due to its portability, wearability and low cost, could be the right path towards an increasingly green IoT (
Figure 1).
Figure 1. Flexible electronics is an important building block for the creation of a sustainable and interconnected world.
2. Green Substrates: Paper and “Nanopaper”
The choice of the substrate on which to make a flexible device is surely a key factor for sustainable IoT because the greater quantity of material that makes up the device is precisely the substrate
[103].
With the advent of flexible electronics, the favored substrates on which to build devices have, for a long time, been plastic materials. However, discarded plastics degrade to form micro and nano-plastics that are hazardous to human beings and the environment. If one thinks of the implementation of flexible devices that are “green”, surely paper is the first material that comes to mind as a substrate to substitute plastic
[104]. In fact, paper is widely and easily available, low-cost, recyclable and biodegradable.
Table 1 shows a comparison between paper and the plastic materials mostly used as substrates, in terms of impacts on climate change and resource use
[105]. In this regard, it may be useful to recall that studies conducted on these same indicators as regards the production of silicon, the fundamental semiconductor in the electronics industry, have highlighted a development in the wrong direction for the silicon industry, facing increasing climate related pressures
[106].
Table 1. Comparison between paper and the most used plastic substrates, in terms of the impact on climate change and resource use.
Substrate Material |
Climate Change Impact kg CO2 eq. */Sheet *** |
Resource Use kg Sb eq. **/Sheet *** |
an interesting comparison is made between different paper substrates and PET substrates. The main results are summarized in Table 2.