As a disease of the circulatory system, cardiovascular disease includes heart disease and vascular disease. The main diagnostic methods for heart disease include invasive and non−invasive examinations [53]. Invasive tests, including cardiovascular endoscopy, endomyocardial biopsy, and other studies, which may cause trauma to patients, come with certain risks. Noninvasive investigations, including ECG and echocardiography, are not traumatic, but have low diagnostic value and diagnosis cannot be performed in real time over a long time. Therefore, finding new diagnosis methods is key to solving these problems.

Blood pressure detection is a key means of diagnosing cardiovascular diseases. Effective long-term collection blood pressure data could help to analyze personal health changes, thus assisting in determining the causes of diseases. Doctors are able to analyze patients’ comprehensive physical conditions on the basis of long-term data, and provide constructive suggestions with the aim of providing patients with personalized medical care. TENG-based blood pressure monitoring instruments are not only characterized by the use of lightweight and safe raw materials, they are also able to guarantee the long-term stable operation of the instrument because of its self-powered characteristics. Ran et al. developed a cuff-free, self-powered continuous blood pressure monitoring system. The system was based on a new double sandwich structure (a copper electrode sandwiched between two layers of silicone rubber and cardboard is added at the outermost layer to provide support) [54]. Using the adaptive design described above, this system was able to achieve a sensitivity of 0.89 V/kPa, and a response time of 32 ms; this sensor was easily able to capture blood vessel signals, and could be used for long-term and efficient real−time blood pressure diagnosis.

Real−time pulse diagnosis can be used to provide doctors with continuous information on the pulse rhythm information of patients. On the basis of the analysis of this information, clues can be found as early as possible of certain cardiovascular diseases, such as atrial fibrillation, supraventricular tachycardia, premature beats, etc., and they can be treated in a timely fashion. At the same time, long-term pulse information can indicate direction for doctors to follow in analyzing the heart rhythms of patients, thus providing strong support for the further personalization of the treatment of patients. Xu et al. designed a self-powered sensitive ultra-pulse sensor (SUPS) that could be used to conduct long-term non-invasive real-time cardiovascular monitoring [55]. The device uses an FEP film consisting of a nanowire array and a Polyamide (PA) film with a fiber structure as the triboelectric layer, copper foil as the electrode, with the addition of a melamine sponge with a porous structure as an interlayer between the triboelectric layers. As a result of the adaptive design described above, SUPS showed excellent sensing performance, including a super sensitivity of 10.29 nA/kPa, a low detection limit of 5 mg, and a rapid response time of 30 ms. It can be used to monitor cardiovascular systems in a long-term, stable and accurate manner, and is expected to be used in the diagnosis and prevention of cardiovascular diseases.

Wang and his team proposed a flexible pressure sensor (FPS) for measuring the pulse of the cutaneous artery [56]. PTFE, copper powder, and conductive double-sided adhesive were used to perform detection following the TENG principle, and this was demonstrated to be suitable for the diagnosis of cardiovascular disease. This device was produced by means of a convenient coating operation, by which a copper powder layer with a natural microstructure with a 500-nanometer scale was formed on a conductive double-sided adhesive. This hierarchical microstructure was composed of copper powder, making the FPS sensitive to weak pressure signals; the FPS had a high sensitivity of 1.65 V/kPa, and was able to accurately detect arteries over a long period of time, thus making it useful for the diagnosis of cardiovascular diseases.

Presently, a variety of methods can be employed for the diagnosis of respiratory diseases, including imaging diagnosis and endoscopy [57,58,59]. However, these conventional detection methods are not able to transmit the progress of disease in real time in cases of long-term diseases such as chronic rhinitis and pharyngitis. This leads to doctors being unable to quickly change treatment strategies, which affects the efficiency of treatment. In addition, the costly and time-consuming nature of testing equipment also affects patients’ quality of life to varying degrees. New breath detection devices based on TENGs could find easy application for long-term operation due to their being self-powered and stable. In addition, because of their small size, light weight, and other advantages, they can be customized to a certain extent depending on the individual needs of patients, thus minimizing their impact on the lives of patients. For example, Zhang and his team proposed a TENG for use in the self−powered detection of exhaled gas and disease diagnosis [60]. The TENG was made of Ti₃C₂Tx MXene/amino functionalized multi-wall carbon nanotubes (MXene/NH₂-MWCNTs). It was driven by respiration, and could be used to determine the type of respiration on the basis of voltage changes in order to diagnose respiratory disease. Furthermore, on the basis of the long-term respiratory data collected, the physical condition of the patient and disease progression can be analyzed in detail. Additionally, since MXene/NH₂-MWCNTs are sensitive to formaldehyde gas, the device is also able to accurately detect formaldehyde gas in exhaled gas, which could play an important role in the determination of air safety.

Gram−positive bacteria such as Staphylococcus aureus can cause a series of diseases, such as upper respiratory tract infection, suppurative tonsillitis, bronchitis, pneumonia, and skin and surgical incision infections. They pose a significant challenge to human medical treatment. In addition, most bacterial infections cause a deterioration in the patient over time. Early detection and treatment can reduce wastage of medical resources and effectively reduce the severity of sequelae. Considering that routine invasive testing increases the risk of multiple infections in patients, it is urgently necessary to find non−invasive and efficient detection methods, including surface-enhanced Raman spectroscopy (SERS) and highly sensitive detection methods using TENGs.

Ma and his team, using Au@Ag NPs/slide as an enhanced substrate, constructed an aptamer-based SERS method for detecting Staphylococcus aureus. The ROX-aptamer of S. aureus was modified on the surface of Au@Ag NPs/slide by means of electrostatic interaction [61]. Because the aptamer is able to specifically bind to Staphylococcus aureus, it will cause the rox-aptamer to fall off the substrate surface, thus reducing the SERS signal intensity of the substrate. Then, the target bacteria can be successfully detected by analyzing the signal changes of SERS.

In this regard, Wang et al. developed a TENG especially for detecting Gram-positive bacteria in solution in order to be able to diagnose relevant diseases in time [62]. The system immobilized polyamine and vancomycin on the etched surface of ITO glass and recognized Gram-positive bacteria by means of vancomycin bacterial wall interaction. Guanidine-functionalized multi-wall carbon nanotubes (CNT Arg) were used as signal amplification materials. Then, the system was able to specifically detect Gram-positive bacteria in solution by measuring the voltage change in the biosensor. This equipment could be used to observe Gram-positive bacteria stably over a long time, and can be applied for the diagnosis of diseases resulting from infection with Gram-positive bacteria or for the determination of water quality in the future.

Obstructive sleep apnea-hypopnea syndrome (OSAHS) affects about 1 billion people worldwide. This disease can cause repeated upper airway collapse during sleep, further leading to intermittent hypoxia, sleep disorders, and even cerebrovascular diseases. At the same time, most OSAHS remains diagnosed. To solve this problem, Peng et al. prepared a respirable electronic skin (SANES) based on TENGs for real-time respiratory monitoring and diagnosis of OSAHS [63]. It was prepared using gold as an electrode, multilayer polyacrylonitrile, and “polyamide 66” nanofiber as positive and negative friction electrodes; the highest pressure sensitivity obtained was 0.217 kPa⁻¹, and it also showed good air permeability. Therefore, the electronic skin was able to achieve accurate breath detection. At the same time, the team further developed a self−powered diagnostic system for the assessment of OSAHS severity. The automatic diagnostic system was able to diagnose OSAHS in real time, effectively prevent the occurrence of OSAHS, and improve sleep quality.

Parkinson’s disease is a common degenerative disease of the elderly nervous system that leads to motor disorders in patients. At present, doctors mainly rely on careful observation to assess the development of the disease. Therefore, Kim et al. synthesized a highly stretchable and self-healing hydrogel TENG with natural biomaterials (catechol chitosan was mixed with pill-shaped diatom frustules with sizes of 20–50 µm) [64] that had an instantaneous power density of 29.8 mW/m². The TENG obtains energy from human motion and combines it with the M-type Kapton film to form a self-powered tremor sensor. The sensor was able to diagnose and monitor Parkinson’s disease through the measurement of the low-frequency motion of patients in combination with machine learning algorithms. The individual needs of different patients can be met by changing the appearance structure. At the same time, Yuce et al. developed a self-powered TENG for diagnosis of Parkinson’s disease [65]. This nanogenerator was made of flexible materials, and through customization was able to meet the need for patients to be able to wear it for a long time. It consisted of a 4 cm × 3.5 cm dielectric and 2 mm × 3 mm aluminum electrodes. When the patient’s hand bends, the system generates voltage due to the change in the relative position of the dielectric material and the aluminum electrode. This sensor can be used to evaluate the patient’s condition, and can be worn for long-term monitoring due to its self-powering characteristics.