## 4 Applications of Piezoelectric Materials in Analytical Chemistry
### COVID-19 Detection  
People's lives have changed all around the world as a result of the severe acute respiratory syndrome coronavirus (SARS-CoV-2) outbreak, which has had a profound effect on economies and communities. As illustrated in Figure 30, new techniques have recently been created to detect SARS-CoV-2 [141].  
Figure 30: Methods for SARS-CoV-2 detection reproduced with permission from [141], Elsevier, 2011.  
Figure 29: (**a**) Surface acoustic wave sensor for the detection of influenza-A virus devised by [PERSON] et al. [139]. (**b**) a piezo diaphragm-based immuno-assay chip for the detection of the hepatitis-B virus created by [PERSON] et al. (**i**) SEM image of the manufactured chip, (**ii**) backside view, SEM image of the (**iii**) top view and (**iv**) cross-sectional view created by [PERSON] et al. reproduced with permission from [140], Elsevier, 2015.  
By 2030, it is predicted that the IoTs and AI will have a significant economic influence and become progressively more in demand in the upcoming post-corona society. For instance, AI-enabled IoT-connected biosensors may proliferate. Currently, there is a need for the creation of reliable and effective piezoelectric biosensors that can detect SARS-CoV-2. In fact, it has been reported that SARS-CoV can be detected using a piezoelectric immunoassay [142] and applying the recently suggested surface chemistry to the surface of quartz crystal of the quartz crystal microbalance will enable the rapid detection of the SARS-CoV-2, Figure 31[143].  
The spike protein has hydrophobic and positively charged residues of amino acids at its protein binding sites. As a result, it is anticipated that a surface that is hydrophobic and negatively charged will adsorb or attach to the spike protein because of the strong electrostatic and hydrophobic interactions. The best-engineered surface used for this purpose appears to be mixed self-assembled monolayers of COOH and CH3 groups. For the real-time detection of the SARS-COV-2 with a sensitivity up to the ng range, the described surface chemistry could be applied to the quartz crystal surface of the quartz crystal microbalance. A piezoelectric microcantilever biosensor was developed for the immediate detection of COVID-19 without the need for any pre-treatment. The associated antibody is coated on the biosensor, which serves as a transducer. A piezo-electric microcantilever bio-sensor function based on the interactions between SARS-CoV-2 antigen and antibody. Through their spike proteins, the SARS-CoV-2 antigens adhered/attached to the microcantilever top surface. Different piezoelectric materials were assessed in order to create a biosensor with the optimum parameters. Consequently, it was determined that a PVDF biosensor provided the optimal result. As a result, the rapid detection of COVID-19 in clinical samples with different viral loads is made possible by the extremely sensitive microcantilever biosensor [144]. Piezoelectrics are attractive candidates for self-powering biosensors for the detection of viruses and communication by harvesting energy from environmental sources. Wearable biosensors should be integrated with the energy harvesters to provide a self-power source. By automatically gathering and transmission of data, such multi-function self-powered devices may be able to control health, making it possible for people to live without the fear of acquiring numerous viral infections. A representation of this type of future society is seen in Figure 32[134]. Wearable actuators might be capable of guiding individuals away from dangerous situations. The energy required could be generated by the breeze. AI may be able to anticipate the severity and the rate of disease spread.  
Figure 31: Schematic representation of engineered surfaces that could be applied to the quartz crystal surface of the quartz crystal microbalance for the rapid detection of SARS-CoV-2 reproduced with permission from [143], Elsevier, 2011.