Page 502 - IJB-10-3

International Journal of Bioprinting 3D printing microgroove nerve conduits

2.10. Statistical analysis lower polymer concentration solutions produced films with
Statistical analysis, specifically one-way analysis of variance a smoother appearance (Figure S2 in Supplementary File).
(ANOVA) with Tukey test, was carried out using Origin To demonstrate the feasibility of this approach to
software (OriginLab, USA). The data are expressed as the fabricate NGCs, the film was rolled around a mandrel
mean ± standard deviation. The significance levels were set and sealed with an adhesive to form a tube with an inner
at *P < 0.05, **P < 0.01, and ***P < 0.001 when comparing diameter of 1.7 mm and length of 12.5 mm (Figure 2d-i
PCL and PCL/PLA with the same groove parameters.
and 2d-ii). SEM showed uniform microgroove structures
3. Results and discussion on the inner wall of the NGC that act as topographical
guidance pathways (Figure 2d-iii) and a clean seal (Figure
3.1. Morphology of moulds and microgroove films 2d-iv). The tube was flexible and has dimensions suitable
Light microscopy and SEM were used to evaluate the for NGC applications, warranting further study.
suitability of 3D printing to fabricate micropatterned An alternative 3D printing system (M-50,
master moulds for the casting of PDMS moulds and CADworks3D, Canada) based on digital light processing
subsequent solvent casting of microgroove substrates
(Figure 2). The microgroove dimensions (width, spacing, (DLP) technology was similarly evaluated to determine
and depth) of the master moulds and corresponding the machine system specifications required to achieve
PDMS moulds and microgroove films are depicted in dimensions suitable for NGCs (Figure S3 and Table S2
Table 1 and Table S1 (Supplementary File), based on in Supplementary File). 3D-printed master moulds with
the use of light microscopy and LSCM, respectively. microgroove dimensions of 100/100/50 µm, 150/150/50
The depth measurement accuracy is limited due to the µm, and 200/200/50 µm were achievable, but a smaller
limitations of light microscopy on these types of samples. microgroove of 30/30/10 µm was not possible. Further
Qualitative and quantitative observation of the 3D-printed study was discounted due to the inability of achieving a
master mould shows a highly ordered, smooth, and well- resolution suitable for NGCs.
defined microgroove architecture that closely matches the The use of PµSL to fabricate microgroove topographies
design parameters (Figure 2a). Flat 3D-printed master offers significant advantages and comparable results
mould and flat PDMS mould were fabricated as a control compared to conventional approaches such as
(Figure S1 in Supplementary File). These dimensions photolithography, soft lithography, and electron beam
are closely transferred to the PDMS mould, and the lithography that have been utilised up till now. The lower
microgrooves are clear and uniform, although surface production cost, shorter experimental time, ease of access,
deviations and imperfections are visible due to the casting and greater design freedom can allow more complex 3D
process (Figure 2b). This evidently demonstrates the structures to be fabricated for use in casting rather than
suitability of (PµSL) 3D printing for the fabrication of traditional planar substrates. However, the PDMS mould
microscale master moulds for microgroove patterning. degrades with multiple exposures to the solvent. Thus,
The microgroove thin films consisting of PCL and differences between batches are possible, and the PDMS
PCL/PLA at different concentrations (1, 3, and 5 wt%) mould should be replaced once noticeable deterioration in
and dimensions were successfully fabricated using solvent microgroove quality is observed.
casting (Figure 2c; Figure S2 in Supplementary File). As 3.2. Surface roughness
observed, the films present microgroove dimensions The surface roughness of the microgroove films with
similar to the original design and the PDMS and 3D-printed different concentrations was evaluated using AFM with
moulds. The microgroove surfaces are smooth; however, a scan area of 0.5 µm (Figure 3a). The mean roughness
2
there is a slight irregularity to the groove shape, which is (Sa) values of the 3 wt% PCL, PLA, and PCL/PLA
not perfectly straight but is similar to other comparable surface are 8.31 nm, 4.28 nm, and 4.20 nm, respectively.
microgroove PCL and PCL/PLA films. 29,49 Micro- and The addition of PLA reduces the surface roughness,
nanoscale pores are observed on the lower groove surface agreeing with the SEM observations. The 1 wt% samples
due to the rapid evaporation of DCM causing bubbling show consistently lower surface roughness than the 3
(Figure 2c, inset). Whilst the upper grooves have the and 5 wt% films. There is a change in nanoscale features
presence of nano-fissures, potentially due to the greater
thickness of material at this area and a slower evaporation from a relatively homogenous and smooth appearance
at 1 wt% to a more spherical and undulating surface at
rate during casting. To attenuate the rapid evaporation, higher concentrations.
a multi-solvent system can be explored to optimise the
solvent casting process. The addition of PLA generally LSCM was used to map the 3D topographic surface of
reduced the appearance of pores and fissures. Similarly, the 3D-printed master mould and microgroove films at

Volume 10 Issue 3 (2024) 494 doi: 10.36922/ijb.2725