# Wearable Sensors for Vital Signs Measurement: A Survey
## 3 Intelligent Prospect of Wearable Medical Sensors
### Intelligent Prospective Applications of Wearable Medical Sensors
#### 3.2.2 Prospects of Material Research for Wearable Medical Sensors  
In the current medical field, most medical robots use an industrial robot as the operating platform, and it is difficult to achieve high levels of accuracy, replicability and reliability [61, 62]. Nowadays, through mechanical structure, hardware design, and software optimization, medical robots have achieved, to a certain extent, the characteristics of flexible operation, and high levels of human-computer interaction and replicability for clinical operations. Generally, robots touch or intervene in human tissues during minimally invasive surgery. If the patient makes an involuntary movement, it is likely to affect the position and shape of the robot in the human tissue, so that the failure of the operation is likely to occur, and it is more likely to cause inevitable trauma to the subject [63]. Therefore, it is also extremely important to innovate materials, while improving the performance of medical intelligence. Many researchers have conducted investigations in this area. In view of the fact that real-time detection of low-concentration acetone vapor plays a decisive role in the early diagnosis of diabetes, [PERSON] et al. (2018) fabricated a zoom medical sensor by  
Figure 4: Framework diagram of IoT security system based on wearable medical sensor network. using nanoscale porous crystal. They found that when the material was used as a wearable sensing material, it showed sensitivity and selectivity to acetone gas, which provided a basis for the manufacture of wearable medical sensors in the environmental and medical fields [64]. [PERSON] et al. (2019) analyzed a simple hydrothermal method for the synthesis and characterization of nanodisks. Morphological characterization confirmed the formation of clear nanodisks of high density and an average thickness of 60 microns. A wearable medical sensor was prepared, with a synthesized nanodisk as the electrode material. They found that the gas-sensing response, response time, and recovery time of the prepared wearable nanodisk gas sensor were 16.25 s, 52 s, and 41 s, respectively. The nanodisk was expected to be a candidate material for manufacturing wearable medical sensors for efficient toxic and harmful gas detection [65]. [PERSON] et al. (2020) prepared a green conductive Ag nanowire (AgNW)/cellulose nanofiber (CNF) hybrid nanopaper by using surface solution mixing and vacuum filtration technology to prepare flexible sensors. Two different types of strain sensors were designed to study their application in strain sensing. They showed great potential in human motion and physiological signal detection. In addition, when mixed nanopaper was used as a wearable temperature sensor, it also showed stable and replicable negative temperature-sensing behavior, which provided guidance for the manufacture of flexible and biodegradable wearable sensors [66]. [PERSON] et al. (2020) analyzed three nanocomposite thick-film flexible gas sensors made of reduced graphene oxide (RGO), tin oxide (SnO\({}_{2}\)), and polyvinylidene fluoride (PVDF). Chromium (Cr) was deposited on the surface of the device by an electron beam evaporation system to form the electrode of the device. The crystal structure, morphology, and electrical characteristics of the device were explored for the application of body temperature measurement. The results suggested that the sensor response was 49.2% and 71.4% sec, respectively, and the sec of 100 ppm and 1000 ppm hydrogen concentration were obtained, respectively. A novel low-cost flexible polymer-based nano wearable sensor was explored for the first time [67]. [PERSON] et al. (2021) synthesized a layered flower-like nickel-doped polymer using a one-step coprecipitation method and prepared a gas sensor, based on the prepared material, to evaluate its gas-sensing performance. The comparison revealed that the sensor showed excellent moisture resistance and long-term stability.