# Borophene Is a Promising 2D Allotropic Material for Biomedical Devices
## 2 Main Properties of Borophene
### Borophene in Electronic Applications for Medical Devices  
The polymorphism showed by 2D boron is quite different from the other 2D materials; the substrate created on its surface plays a key role in the structural stability of borophene. Borophene can have different energy spectra depending on the type of metal substrate [19], and metals with different bases of borophene \(\beta_{12}\) such as Ag, Cu, Au, and Ni can develop energies ranging from 0.4 to 2.1 meV, or from 15.1 to 28.9 meV. The above-reported behavior allows us to define the degree of polymorphism shown by borophene properly.  
Due to the low mass of boron, a strong electron-phonon coupling can amplify the superconductivity of phonons and their propagation. Moreover, the hexagonal molecular geometry that characterizes the structure of borophene and the different critical temperatures, ranging from 10 to over 20 K, are the parameters that make borophene a superconductor [20]. In fact, superconducting transition temperatures have been found to be much higher than theoretically predicted and experimentally observed in other similar materials, such as graphene.  
As previously stated, the different forms of borophene hold different properties that allow their application in many different biomedical fields, and the ability of borophene to act as an energy source in combination with other materials is promising for the production of electronic biomedical devices requiring a long-lasting charging, such as implantable or wearable devices. Of course, this application needs to be improved, especially in the charge/discharge processes, in regards to the safety of such high-capacity charging, in terms of charge duration, and so on.  
In this context, an important role could be played by borophene in the phase of _2-Pmmm_. In a recent study, _2-Pmmm_ borophene was considered to be a good anode for Li-ion batteries because of the massive oxidative processes that this specific material are able to promote; moreover, _2-Pmmm_ borophene ensures an elevated conductivity that allows a charge/discharge process without any energy dispersion [21]. Some modifications to _2-Pmmm_ borophene, such as doping, hydrogenation, or stratifications, may affect the interactions among borophene and other different materials; for example, a lower efficiency is reached between Li and hydrogenated borophene. On the other hand, in Li-Sulfide (LiS) batteries, the use of \(\beta_{12}\) and \(\chi_{3}\) borophene impacts the levels of energy stored. Specifically, the borophene adapts its structure to absorb energy within LiS batteries, thus reducing the alteration of the structures during the charge/discharge cycles. It is also worth noting that \(\beta_{12}\) borophene within LiS batteries has shown overall structural stability, even if it seems to ensure a lower adsorption of energy [22].  
Excellent results have also been obtained in supercapacitors made with several layers of borophene [23], even after more than 6000 discharge cycles. The use of these multi-layered borophene-based supercapacitors is promising in medical devices, with a special interest towards the rehabilitative robotics, where the storage of energy is fundamental to ensure a correct functionality over time. Furthermore, biomedical implantable devices (IMDs) [24] often require the use of an external charger, and borophene-based technologies can significantly reduce charging time from hours to minutes, thus reducing the limits of these technologies. The use of hybrid power, consisting of LiS and \(\beta_{12}\) batteries, when applied to IMDs will ensure faster charge/discharge cycles; furthermore, the supercapacitors will allow the storing of a higher quantity of energy, which could be used as a strategic energy reserve, especially in devices that need to last for long periods.