# Strategies for Enhancing Extracellular Electron Transfer in Environmental Biotechnology: A Review
## 3 Strategies for Enhancing EET in Environmental Biotechnology
### Integrated Strategies for Enhancing EET  
Presently, there is a growing interest among researchers in investigating the integration of different modalities to enhance EET and improve the performance of MES. Here we present the various contemporary technologies that can be integrated with BESs to enhance its efficiency. 1. Additive manufacturing (AM): AM, commonly referred to as 3D printing, is a rapidly advancing technological innovation that has made significant contributions to MFC technology in recent times. A study by [PERSON] et al. [97] (Figure 5) explored the limits of AM technology in the creation of a powering device that is entirely based on AM. The study focused on utilizing low-density and open porosities to accommodate microorganisms, as well as developing systems that are easily fueled continually and operate securely. A maximum energy recovery of approximately 3 kWh m\({}^{-3}\) per day was achieved, which is capable of supplying power to sensing devices and low-energy electronic gadgets. This facilitates data conveyance and analysis from remote and challengingsituations. AM facilitates the design for the assembly of MFCs, thereby mitigating mistakes as a result of human intervention and expediting the installation procedure. In a study by [PERSON] et al. [98], AM techniques were also employed to construct an MFC with the incorporation of an exchangeable membrane slot. This enabled them to examine the effects of different separator membranes. The utilization of AM in the production of tango membranes has demonstrated promising prospects for membrane manufacturing and power-generating capabilities. However, it is worth noting that the power output achieved (0.92 uW) by this method was relatively low in comparison to the conventional cation exchange membrane technology (11.39 uW). Similarly, [PERSON] [99] investigated enhancing the power outputs of MFCs with the integration of graphene into electrodes fabricated using 3D printing technology. The electrodes underwent an evaluation to assess their electrical efficiency, chemistry, and appearance, thereby showcasing the prospective application of AM in the production of MFCs. Furthermore, AM technology, such as inkjet printing, was used in a study by [PERSON] et al. [100]. The research showcased the practicability of employing a readily available commercial inkjet printer for the production of a thin-film paper-based biphotovoltaic cell. This cell comprised a layer of cyanobacterial cells positioned above a conducting surface composed of carbon nanotubes. The researchers discovered that the printed cyanobacteria can produce a continuous electrical current for a duration exceeding 100 h. This phenomenon occurs both in the absence of light, functioning as a \"solar bio-battery\", and in the presence of light, functioning as a \"bio-solar-panel\". These findings suggest its possible use in low-power devices. The utilization of the inkjet printing technique facilitated precise positioning of the cyanobacteria onto the anode surface, hence facilitating the proximity of the printed cathode. The printing technique was optimized to achieve ideal biofilm layer thicknesses to maximize power generation. The aforementioned authors were pioneers in employing an inkjet printer to print photosynthetic microorganisms, specifically cyanobacteria, onto a bio-photovoltaic (BPV) cell. Consequently, AM offers the potential to utilize diverse materials and 3D printing techniques to develop a comprehensive MFC tailored to different applications. This helps to expedite the optimization process of individual MFC components, leading to enhanced effectiveness and ease in reactor design and consequently, the system will experience functional improvements. AM has the potential to significantly impact the field of biological power generation devices due to its advantages such as decreased lead time, enhanced design flexibility, cost-effectiveness, and expedited prototyping capabilities. In addition, AM offers a shorter route from the research laboratory to large-scale production.