## 4 Integration into IoT
### Cyber-Physical Systems  
A city's IoT today is often associated with cyber-physical system (CPS) applications [87; 122]. Many mentioned approaches can be described as CPSs, including automated vertical farms, which are widely described in the scientific literature [26; 87]. In this section, CPSs related to biosensor and bioactuator approaches are the main focus.  
As shown earlier, biotechnology provides the ability to make sensor systems more autonomous in terms of self-activation and preliminary data analysis. In some cases, such systems require unique methods of handling. Regarding self-powering MFC-based biosensors, MFCs, used for a biosensor's power supply in rain gardens and green streets, can start their operation and then water flow with organic impurities will arise in the system. After the rain ends, the water flow disappears and the MFCs shut down. The time of system operation can be controlled by using an additional battery to collect energy and select the power output of the MFCs [18]. Thus, the bioenergy source-based regulation of sensor operation can be realized, so more distributed and more autonomous WSNs can be developed.  
As shown in Figure 3, multi-sensor cell systems with several stages of data processing include multiple stages in genetic logic circuits and cell-to-cell communications. As mentioned, there are many issues related to the application of those sensor systems that need to be solved. The development of digital twins of such sensors can be one of the ways of solving some of the mentioned issues. HLM operation also requires some predictability when operating in an open environment. HLM users should be sure that, as a result of the work, they receive necessary results without any negative consequences. Moreover, the predictability of synthetic biology-based biosystems is one of the key issues that make legislation regarding its application less prohibitive [74; 123; 124]. The prediction operation of those systems faces difficulties related to the complexity of the intracellular process [125]. Thus, to decrease the complexity of model approaches, the requirements of simulation processes need to be highlighted. It was mentioned earlier that simulations using analog electrical circuits can help to solve these issues. Thus, how this system with digital twins can operate will be discussed here, where on/off self-healing for polymeric materials will be used as an example (Table 2). Figure 5 illustrates an example of an HLM application. There are two WSNs applied in this system: one is a WSN for environmental control, and the other is much smaller for HLM control and includes optical sensors. When a signal from the environment (for example, chemical) arises, cells begin biopolymer production and fluorescent protein biosynthesis as a signal that they can start operating. This is a signal from cells, and it changes in HLM due to arising biopolymers that are registered by the HLM WSN. Digital twins provide simulations of HLM processes, are based on measurements from WSN data, and result in simulation control action development. Control action can consist of adding biochemicals that influence HLM operation. Thus, additional WSNs to control HLM are necessary to provide measurements and receive data that will be compared with digital twin simulations results.