3d lightyear software v1

A commercial stereolithography apparatus (SLA, 250/50, 3D Systems) was modified for polymerization as previously described.⁹ (link) Parts generated using computer-aided design software were exported to 3D Lightyear software (v1.4, 3D Systems), which sliced the part into layers. Prepolymer solutions for biobots and holders are described previously.³ For fabrication of biobots, an 18 × 18-mm² cover glass was secured to the center of a 35-mm culture dish before fabrication. For biobot holders, cover glass slides were first treated with 2% (vol/vol) 3-(trimethoxysilyl)propyl methacrylate (EMD Millipore) in 200-proof ethanol (100% EtOH) for 5 min and then washed with 100% EtOH for 3 min, dried, and secured to the center of a 35-mm dish. Following fabrication, each structure was rinsed with PBS, sterilized in 70% EtOH for 1 h, and allowed to re-swell in PBS for at least 1 h. This protocol has been previously published with additional details.^9,64 (link)

Bio-bot skeletons and holders were fabricated using a commercial Stereolithography apparatus (SLA 250/50, 3D Systems)^{4 (link)}. Briefly, parts were designed in CAD software (AutoCAD), exported in. STL format for slicing into layers (3D Lightyear software, v1.4, 3D Systems) and built in a layer-by-layer fashion on a modified SLA stage^{56 (link), 57 (link)}. To print hydrogel beams with varying stiffness profiles, the polymerization energy dose of the SLA (108.7 to 233.3 mJ cm⁻²) was adjusted according to a Working Curve Equation^{29 , 30 (link)} in order to obtain elastic moduli of 214 to 489 kPa, as detailed earlier^{4 (link)}. Liquid hydrogel formulations were not altered. A skeleton beam of 319 kPa was used unless otherwise noted.
Liquid pre-polymer hydrogel solutions were composed of 20% poly(ethylene glycol) diacrylate of M_W 700 g mol⁻¹ (PEGDA 700, Sigma-Aldrich) or poly(ethylene glycol) dimethacrylate of M_W 1000 g mol⁻¹ (PEGDMA 1000, Polysciences, Inc.)^{4 (link), 5 (link)}. After fabrication, skeletons and holders were sterilized in 70% EtOH and stored in sterile PBS.