# A Review on Recent Trends and Applications of IoT in Additive Manufacturing
## 2 IOT-Enabled 3D Printing Applications
### 3D Bioprinters  
The use of additive manufacturing in biological matter formation, such as cells, tissues, blood cells, etc. is called 3D bioprinting. Bioprinters operate virtually similarly to 3D printers, with one key distinction. Rather than delivering items such as plastic, ceramic, metal, or food, they deposit layers of biomaterial, which may contain living cells, to construct complex structures such as blood arteries and skin tissue. Currently, the majority of 3D bioprinting materials are derived from either natural or synthetic biomaterials. Bioactivity is the primary benefit of organically derived materials (such as collagen, chitosan, gelatin, hyaluronic acid, alginate, and fibrin). They often have a high degree of resemblance to the extracellular matrix (ECM) and are biocompatible. The IoT helps to avoid the delay in producing the organs. If we fully use IoT technology in bioprinting, then we can decrease deaths due to organ damage in accidents. For example, if a person's heart is partially damaged then with the help of IoT sensors and systems we can understand the complete requirements of the damaged heart, then those parameters can be given as the input to the bioprinters so the new synthetic heart is made before the damaged heart fails completely. However, natural biomaterials are frequently poor in terms of their mechanical qualities, even after cross-linking. Synthetic materials (such as PCL, PEG, PLA, PEEK, and Pluronic) have better advantages over natural materials because they can be designed with specified physical qualities and have more uniformity [63]. For use in medical treatments, training, and testing, bioprinting may generate living tissue, bone, blood arteries, and potentially complete organs. Cell development and several bioprinting methods are depicted in Figure 11.  
Figure 11: ITOP systems with various bioprinters (**A**) process flow chart (**B**) 3D printed object (**C**) 3D printing process using CAD model and (**D**) 3D printing bath with syringe head (**E**) quality assurance of the 3D printed organs [64]. In the early stages of healthcare, the loss or failure of organs and tissues is a challenging and expensive issue. Worldwide organ shortages have prompted research on tissue engineering, specifically the building of a cell-scaffold microenvironment to stimulate the regeneration of diverse types of tissue, such as skin, bone, cartilage, tendon, and cardiac tissue [65]. Currently, it is not possible to bioprint completely functional organs for transplantation in three dimensions. Figure 12 illustrates the development of bioprinting. However, it is undeniable that bioprinting processes have developed substantially. Several pioneers, including [PERSON], [PERSON], and [PERSON], anticipated decades ago that the natural combination of technologies, including cell patterning and commercial inkjet printing, for the construction of living structures may one day be used in human organ transplantation [66]. Year 1984 marked the start of 3D printing when [PERSON] pioneered stereolithography (SLA) for printing 3D applications from digital data. Bioprinting was shown for the first time in 1988 when [PERSON] utilized a conventional Hewlett-Packard (HP) inkjet printer to deposit cells using cytoscribing technology [68]. [PERSON] and colleagues [69] concluded in 1996 that apparent tissue surface tension was the macroscopic expression of molecular adhesion between cells and gave a quantitative measure of tissue cohesion. [PERSON] and [PERSON] exploited laser-assisted bioprinting to deposit living cells for the development of mimics with complicated anatomy for the first time in 1999 [70]. The year 2001 saw the direct  
Figure 12: Bioprinting evolution timeline [67]. printing of a bladder-shaped scaffold and the implantation of human cells [71]. In 2002, [PERSON] et al. revealed the first extrusion-based bioprinting method, which was eventually commercialized as the \"3D-Bioplotter\" [72]. In 2003, [PERSON] et al. created the first inkjet bioprinter by adapting a conventional HP inkjet printer [73].