Fig. 2

Sources of error and correction techniques in stereolithography based 3D printing Process. a The 3D printing process begins with a CAD file of the desired part. The part is then b) computationally sliced into layers which are an imperfect approximation of the original part. c) Each layer is then converted into an image that can be projected off of a DLP chip. Because the images are generated using a discrete array of pixels, the image is also an approximation (alias) of the desired object with jagged edges. d When the image reaches the build surface, diffraction and imperfect focus distort the image. These sources of error can be corrected by e) decreasing the thickness of each slice, f) improving image resolution by introducing grayscale (antialiasing) and g) modeling and correcting light distributions (often also employing grayscale). Note that the images in c) and f) show the microneedle being diagonally oriented relative to the DLP chip to exaggerate aliasing for visualization. In reality, images are oriented orthogonally to the DLP chip, as shown in Fig. 1, Additional file 5: Figure S5, Additional file 6: Figure S6 and Additional file 7: Figure S7