A Bio-Based Resin for a Multi-Scale Optical 3D Printing

Abstract

Materials obtained from renewable sources are emerging to replace the starting materials of petroleum-derived plastics. They offer easy processing, fulfill technological, functional and durability requirements at the same time ensuring increased bio-compatibility, recycling, and eventually lower cost. On the other hand, optical 3D printing (O3DP) is a rapid prototyping tool (and an additive manufacturing technique) being developed as a choice for efficient and low waste production method, yet currently associated with mainly petroleum-derived resins. Here we employ a single bio-based resin derived from soy beans, suitable for O3DP in the scales from nano- to macro-dimensions, which can be processed even without the addition of photoinitiator. The approach is validated using both state-of-the art laser nanolithography setup as well as a widespread table-top 3D printer - sub-micrometer accuracy 3D objects are fabricated reproducibly. Additionally, chess-like figures are made in an industrial line commercially delivering small batch production services. Such concept is believed to make a breakthrough in rapid prototyping by switching the focus of O3DP to bio-based resins instead of being restricted to conventional petroleum-derived photopolymers.

Figure 1

Potential applicability and characteristics of AESO. (a) – chemical structures of AESO, diluents Genomer 1122TF and ethyl lactate, PIs IRG369, TPO-L, TPO and BAPO. (b) – an explanation chart for the materials used in optical 3D lithography: Y-left axis – achievable spatial resolution, Y-right – available applications, X-top – required equipment, X-bottom – required irradiation intensities. Images of the objects produced out of AESO-based resin using both DLP and NLL technologies are shown. The numbers 1–3 are marked on the chart to represent how the objects were produced and indicate their potential applications. (c) – measured AESO, AESO + PI(1% w/w)+diluent absorbance and normalized light source emission spectra. Green dashed vertical line marks the wavelength of the laser source. (d) – the dependencies of storage modulus G’ of AESO, AESO-based resins, and PR48 on irradiation time^,. The onset of irradiation (60 s) is marked with violet vertical dashed line.

Figure 2

Assessment of the exposure conditions for the DLP lithography and obtained results. (a) – a scheme of the DLP lithography. DLP experiments data using AESO + BAPO + Genomer 1122TF resin. (b) – normalized energy dose D_p dependence on polymerized films height z. (c) – polymerized films height z dependence on exposure duration t_exp. (d) – a model of a single layer membrane on the pillars. (e) – the model produced out of AESO based resins. (f) – printed membrane: theoretical height 102 μm, measured 97 μm (SEM image). Values of the measured thicknesses of the printed membranes (five black squares) are shown in picture (c).

Figure 3

Manufacturing via NLL and obtained results. (a) – a model of 75 × 75 μm² size bi-layer scaffold structure: T – 30 μm period, p – 15 μm log width, l – 75 μm log length, d – 15 μm distance between logs, d_xy – distance between scans, H – 20 or 30 μm vertical column height, h – 5 μm height between separate column segments, P – applied laser power, v – scanning velocity. (b) – SEM image (at 45° angle) of arrays of manufactured scaffold structures out of AESO. Applied average P was 0.4–0.8 mW (recalculated to intensity I 1.2–2.4 mW/cm²) and is represented in white scale at the bottom. d_xy is shown on the black scale at right. v was set to 5 mm/s. The green area marks well-shaped objects and the red – deformed ones or only their residuals. (c) – representation of the “resolution bridges” (RB) method and ellipsoid shape voxel (green) at the 2w₀ diameter laser beam focal plane. D and L are lateral and longitudinal dimensions of the voxel. (d) – demonstrates a measurement of RB lateral D size (top view). Applied v to form beams was set to 1 mm/s, P was altered in the range 0.1–0.6 mW. (e) – 2D grating in AESO + 0.5% w/w IRG369, v = 0.15 mm/s, P = 0.12 mW, h = 1 μm. D and L sizes are represented in upper-right and lower-left insets, respectively. (f) – 1.065 × 1.065 mm² size 7 layers scaffold: p = 25 μm, d = 105 μm, v = 5 mm/s, P = 0.6 mW; SEM images (at 45° angle) of objects fabricated using P = 0.18 mW: (g) – “Car” model: v = 1.8 mm/s, d_xy = 0.15 μm; (h) – “Tower” model: v = 1.2 mm/s, d_xy = 0.15 μm; (i) – “Marvin” model: v = 1.2 mm/s, d_xy = 0.25 μm. For fabrication of the objects in pictures (b) and (f) 20 × 0.8 NA objective was used, for (d–e) and (g–i) – 63 × 1.4 NA.