# Mini-Review: Recent Technologies of Electrode and System in the Enzymatic Biofuel Cell (EBFC)
## 5 Conclusions  
EBFC has advantages over other fuel cells, such as non-toxic chemical fuel, simplicity, low cost, small size, easy disposal, rapid start-up, eco-friendliness, anti-interference performance, and being easy to operate at room temperature and at neutral pH. However, the electrode materials used must have characteristics such as biocatalytic properties, biocompatibility, biodegradability, implantability, and mechanical flexibility in EBFC. Enzymes that become the heart of the EBFC need to immobilize on the surface electrode. Various methods such as polymer conduction, crosslinking, layer-by-layer assembly, and covalent attachment are used. The current trend mainly uses polymer conduction and crosslinking methods to immobilize the enzyme where the interaction between this material and the enzyme needs to be seen in terms of storage, solvent, pH, and thermal stability, function well, and have high efficiency. However, there is still inadequate and ineffective interaction between the materials used for enzyme immobilization, including imperfect and low enzyme loading, leaching out of enzyme that leads to degradation in long-term operation, potential enzyme poisoning when using non-biocompatibility support materials, reduced lifetime, and limited enzyme stability. Recent studies also use nanoparticle materials to increase electron transfer, although mediators are still used and have higher power performance in EBFCs. However, the mediator also has problems, such as the mediator itself being toxic in the EBFC environment, leakage, producing a low open-circuit voltage (OCV), mediator mobilization, high cost, and instability of the metal ion-based redox. Meanwhile, EBFC systems have various types depending on the use or application of EBFC, such as developing a self-pumping technique suitable for miniaturization applications, while the needle-type EBFCs have been designed to detect glucose poking the needle on the skin. The development of EBFC requires 3D printers due to the quick fabrication process, cost-effectiveness, and simplicity. Therefore, overall, among the combinations of materials that can be studied, namely nanoparticles, graphene, and conductive polymers, these three have the advantage of chemical stability and enhanced electron transfer, and the interaction between these materials can improve EBFC performance. The development of chitosan selection in EBFC is also prevalent in publications because chitosan has the advantages of sensitivity, selectivity, stability, and reproducibility.  
Writing--original draft preparation, N.A.K.; funding acquisition, H.Y. All authors have read and agreed to the published version of the manuscript.  
Figure 8: The series connection of EBFC [86]. Copyright 2020 ACS Publication.  
**Funding:** The authors gratefully acknowledge financial support by the Ministry of Education under FRGS/1/2019/TK02/UKM/02/4. The authors also gratefully acknowledge financial support for this work funded by the Ministry of Science and Technology of Taiwan, grant number MOST-109-2221-E-005-004, and also partially supported by the Ministry of Education of Taiwan under the Higher Education Sprout Project and Southbound Scheme Program.  
**Institutional Review Board Statement:** Not Applicable.  
**Informed Consent Statement:** Not Applicable.  
**Data Availability Statement:** Data sharing is not applicable to this article as no new data were created or analyzed in this study.  
**Acknowledgments:** The help of the crew of Micro/Nano Machining Laboratory, including [PERSON], [PERSON], [PERSON], and [PERSON], with experimental works is appreciated.  
**Conflicts of Interest:** The authors declare no conflict of interest.