*2.3. P*µ*SL Method*

Projection micro-stereolithography (PµSL) is a sophisticated 3D printing method because of its low cost, precision, velocity, and also the variety of the materials such as ceramics, biomaterials, curable

1.3 1.5 3.8 150 1.51

*2.3. PμSL Method* 

photopolymer, polymer, and nanoparticle composites [54]. This method has demonstrated potential in different implementations for example micro-resonators, micro-grippers, micro-optics, biomedical micro devices, micro-fluidics, and so on [57–59]. Studies on PµSL are ongoing in terms of the quality and accuracy of the construction process, which affects the production of complex 3D microstructures and makes it attractive enough to be considered for commercial applications [60]. This technology begins by creating a 3D construction via a computer-assisted design program and then transforms the construction into a set of digital mask images. The working basis of PµSL is shown in Figure 3 [61]. potential in different implementations for example micro-resonators, micro-grippers, micro-optics, biomedical micro devices, micro-fluidics, and so on [57–59]. Studies on PμSL are ongoing in terms of the quality and accuracy of the construction process, which affects the production of complex 3D microstructures and makes it attractive enough to be considered for commercial applications [60]. This technology begins by creating a 3D construction via a computer-assisted design program and then transforms the construction into a set of digital mask images. The working basis of PμSL is shown in Figure 3 [61]. Using a digital micro mirror device as the dynamic mask eliminates the cost of manufacturing a

curable photopolymer, polymer, and nanoparticle composites [54]. This method has demonstrated

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Projection micro-stereolithography (PμSL) is a sophisticated 3D printing method because of its

Using a digital micro mirror device as the dynamic mask eliminates the cost of manufacturing a mask for each layer. Besides, the PµSL method reduces production time since each layer is produced in one exposure, and the time for mask alignment is eliminated. Moreover, this method has the least mechanical moving parts and requires only one accurate *z*-axis motorized linear stage. Consequently, PµSL decreases the cost of construction and protection [62]. mask for each layer. Besides, the PμSL method reduces production time since each layer is produced in one exposure, and the time for mask alignment is eliminated. Moreover, this method has the least mechanical moving parts and requires only one accurate *z*-axis motorized linear stage. Consequently, PμSL decreases the cost of construction and protection [62]. All images symbolize a thin layer of the 3D structure. Along a production period, a single image

All images symbolize a thin layer of the 3D structure. Along a production period, a single image is demonstrated on the reflective LCD panel. The image from the LCD is then mirrored on the liquid surface. All layers (ranging between 5–40 µm thick) are polymerized. When the layer has been solidified, it is dipped in the resin to allow a new thin layer of liquid to form. Repeating the loop forms a 3D microstructure from a layer stack. For the PµSL method, IP-S resin, which is a photopolymer, was used as the material. The properties of the photopolymer resin, which were specially developed for this 3D printer and utilized in the fabrication of the micro beam, are shown in Table 2 [54]. is demonstrated on the reflective LCD panel. The image from the LCD is then mirrored on the liquid surface. All layers (ranging between 5–40 μm thick) are polymerized. When the layer has been solidified, it is dipped in the resin to allow a new thin layer of liquid to form. Repeating the loop forms a 3D microstructure from a layer stack. For the PμSL method, IP-S resin, which is a photopolymer, was used as the material. The properties of the photopolymer resin, which were specially developed for this 3D printer and utilized in the fabrication of the micro beam, are shown in Table 2 [54].

**Figure 3. Figure 3.** Schematic of the projection micro-stereolithography (P Schematic of the projection micro-stereolithography (Pµ μ SL) method [ SL) method [62]. 62].

### **3. Fabrication**

### *3.1. Fabrication with the DLP Method*

The micro beam shown in Figure 4 was fabricated by a DLP technology-based MiiCraft 3D printing device. 3D printing technology entails an input CAD model of the parts that may be designed in software or obtained from reverse engineering such as 3D scanners. When the CAD model of the micro beam is completed, it is transformed into standard STL format, which is most commonly used to *3.1. Fabrication with the DLP Method* 

**3. Fabrication** 

represent 3D CAD models in 3D printing. In an STL file, the CAD model is symbolized using triangular facets, which are described by the x-, y-, and z-coordinates of the three vertices. The step-by-step schema of the 3D printing operation is displayed in Figure 5. The slicer first divides the object into a stack of flat layers, followed by describing these layers as linear movements of the 3D printer extruder, fixation laser, or equivalent. All these movements, together with some specific printer commands like the ones to control the extruder temperature or bed temperature, are finally written in the g-code file, that can be transferred after to the printer. symbolized using triangular facets, which are described by the x-, y-, and z-coordinates of the three vertices. The step-by-step schema of the 3D printing operation is displayed in Figure 5. The slicer first divides the object into a stack of flat layers, followed by describing these layers as linear movements of the 3D printer extruder, fixation laser, or equivalent. All these movements, together with some specific printer commands like the ones to control the extruder temperature or bed temperature, are finally written in the g-code file, that can be transferred after to the printer. During fabrication of the micro beam, the printing parameters for example the layer thickness

model of the micro beam is completed, it is transformed into standard STL format, which is most commonly used to represent 3D CAD models in 3D printing. In an STL file, the CAD model is

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The micro beam shown in Figure 4 was fabricated by a DLP technology-based MiiCraft 3D printing device. 3D printing technology entails an input CAD model of the parts that may be

During fabrication of the micro beam, the printing parameters for example the layer thickness (LT), the light intensity (LI), and the curing time (CT) of all layer significantly affect the print quality. In this study, each parameter is selected for the printing material and TL = 30 µm, and CT = 3 s are set. When the first layer is printed, LI is set to 50% of the brightness to provide a layer bond to the platform. (LT), the light intensity (LI), and the curing time (CT) of all layer significantly affect the print quality. In this study, each parameter is selected for the printing material and TL = 30 μm, and CT = 3 s are set. When the first layer is printed, LI is set to 50% of the brightness to provide a layer bond to the platform.

There are supports to the arms of this design. The number of supports to the arm is 20, the diameter is 3 µm, and the height is 5 µm. Some unsuccessful experiments were done before this design. Breakages were experienced during the manufacturing when the number of supports to the arm was low. Concerning the experiments, the average distance between the supports should be 10 µm to avoid breakages. When the supports are not printed correctly, they cause a collapse and break off the micro beam. An image of the micro beam manufactured with the DLP is shown in Figure 6. This image was taken with the microscope of the 3D printer device. There are supports to the arms of this design. The number of supports to the arm is 20, the diameter is 3 μm, and the height is 5 μm. Some unsuccessful experiments were done before this design. Breakages were experienced during the manufacturing when the number of supports to the arm was low. Concerning the experiments, the average distance between the supports should be 10 μm to avoid breakages. When the supports are not printed correctly, they cause a collapse and break off the micro beam. An image of the micro beam manufactured with the DLP is shown in Figure 6. This image was taken with the microscope of the 3D printer device.

**Figure 4.** CAD design of the micro beam. The structures at the top of the design were designed as support. **Figure 4.** CAD design of the micro beam. The structures at the top of the design were designed as support.

### *3.2. Fabrication with the PμSL Method 3.2. Fabrication with the P*µ*SL Method*

The micro beam shown in Figure 7 was manufactured by a projection micro-stereolithography (PμSL) method based MiiCraft 3D printing device. The manufacturing of the supported design with The micro beam shown in Figure 7 was manufactured by a projection micro-stereolithography (PµSL) method based MiiCraft 3D printing device. The manufacturing of the supported design with the PµSL method was not possible for two reasons. First, the supported structures represent the system as a 3D design. However, it is not possible to fabricate 3D structures with devices of MiiCraft 3D printing, based on PµSL technology. Second, these devices have a resolution of 65 µm and can fabricate a minimum thickness of up to 30 µm.

When the support structures are removed, as shown in Figure 7, it is possible to perform the fabrication as the micro beam design can be introduced to the device (a PµSL technology-MiiCraft 3D

printer) in two dimensions. An image of the micro beam manufactured with the PµSL is shown in Figure 8. This image was taken with the microscope of the 3D printer device. 3D printer) in two dimensions. An image of the micro beam manufactured with the PμSL is shown in Figure 8. This image was taken with the microscope of the 3D printer device.

fabrication as the micro beam design can be introduced to the device (a PμSL technology-MiiCraft

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the PμSL method was not possible for two reasons. First, the supported structures represent the system as a 3D design. However, it is not possible to fabricate 3D structures with devices of MiiCraft 3D printing, based on PμSL technology. Second, these devices have a resolution of 65 μm and can

**Figure 5.** The step-by-step diagram of the 3D printing operation. **Figure 5.** The step-by-step diagram of the 3D printing operation.

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**Figure 6.** Image of the micro beam fabricated with the DLP method. **Figure 6.** Image of the micro beam fabricated with the DLP method. **Figure 6.** Image of the micro beam fabricated with the DLP method.

**Figure 7.** CAD design of the micro beam. The support structures under the micro beam are removed. **Figure 7.** CAD design of the micro beam. The support structures under the micro beam are removed. **Figure 7.** CAD design of the micro beam. The support structures under the micro beam are removed.

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**Figure 8.** Image of the micro beam fabricated with the PμSL method. **Figure 8.** Image of the micro beam fabricated with the PµSL method.

### **4. Conclusions 4. Conclusions**

In this study, a micro beam fabricated with conventional MEMS methods, was manufactured for the first time using the DLP and PμSL methods, which are 3D printing procedures. First, the printable scale of the DLP 3D printing method was evaluated, and it demonstrated that the printer could produce structures with a size of 86.7 μm. In this study, a micro beam fabricated with conventional MEMS methods, was manufactured for the first time using the DLP and PµSL methods, which are 3D printing procedures. First, the printable scale of the DLP 3D printing method was evaluated, and it demonstrated that the printer could produce structures with a size of 86.7 µm.

The experimental studies showed that 3 μm diameter supports were fabricated with the DLP method. However, they could not be fabricated with the PμSL method even when the diameters of the supports were 3 μm. After these support structures were removed, the micro beam was fabricated with PμSL. It was determined that PμSL was not suitable for complex structures. The results show the success of the 3D printer and the suitability of manufacturing a micro beam using the DLP printing method with fast and high sensitivity. The experimental studies showed that 3 µm diameter supports were fabricated with the DLP method. However, they could not be fabricated with the PµSL method even when the diameters of the supports were 3 µm. After these support structures were removed, the micro beam was fabricated with PµSL. It was determined that PµSL was not suitable for complex structures. The results show the success of the 3D printer and the suitability of manufacturing a micro beam using the DLP printing method with fast and high sensitivity.

As a result of this study, it was found that DLP is more appropriate because it allows the manufacturing of complex 3D structures with smaller dimensions, while PμSL is only suitable for simple 2D microstructures. It is expected that this paper will contribute to the literature in terms of fabrication of a micro device through the use and comparison of different techniques. As a result of this study, it was found that DLP is more appropriate because it allows the manufacturing of complex 3D structures with smaller dimensions, while PµSL is only suitable for simple 2D microstructures. It is expected that this paper will contribute to the literature in terms of fabrication of a micro device through the use and comparison of different techniques.

**Funding:** This research received no external funding. **Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest. **Conflicts of Interest:** The authors declare no conflict of interest.

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