Charmet, Jérôme

Couling, Kevin

Dallmann, Robert

Goodship, Vannessa

Middleton, Bethany J.

Warwick Research Archives Portal Repository

Polydimethylsiloxane (PDMS) based devices arecommonly used for Organ on a Chip applications,however they possess serious material propertylimitations [1,2]. In addition, the soft-lithographyapproach [3,4] used to fabricate such devices limitstheir potential translational impact.Injection moulding, which is compatible with awide range of polymers, addresses these issues.However, the high cost associated with micro-fabricated moulds is currently hindering the use ofinjection moulding as a manufacturing option formicrofluidics research applications [5].Here we describe a method, combining 3Dprinting, micro-milling and soft-lithography, todevelop a flexible approach suitable for low-costprototyping of Organ on a Chip devices (Fig 2).B. J. Middleton1, K. Couling1, R. Dallmann2, V. Goodship1, J. Charmet1Low-cost Injection Moulding Strategies for the Fabrication of Organ on a Chip Devices1 Warwick Manufacturing Group (WMG), University of Warwick; 2 Warwick Medical School, University of WarwickIntroductionMethodologyWe acknowledge funding from the Research Development Fund of the University of WarwickMaterialsFabricationResultsNext StepsConclusionsFigure 1: Methodology diagram. Full investigation of these experimental optionswould facilitate low-cost tooling recommendations to be made based on Organon a Chip device requirements.The injection moulder was fitted with a steelbolster tool machined with a cavity toaccommodate a 3D printed tool insert. A 3Dprinted tool insert was manufactured to includethe (injection) moulding cavity and, depending onthe device feature size, a space to accommodatethe patterned inlay. Micro-patterned inlays fit intothe 3D printed insert, so that the patterned surfacecan be injection moulded over.At low cost and with a fast turnaround, differentpatterned inlays can be fitted into the 3D printedinserts and different 3D inserts can bemanufactured to mould different sized parts usingboth standard and micro injection moulding (Fig 1).Pattern replication and lifetime of theinserts/inlays were studied in relation to processparameters.A shortlist of polymers were investigated for theirlow gas permeability (PET), transparency (PS, COC),opacity (PA6) and solvent resistance (PP).In trials so far, PDMS inlays(feature size: 25 µm – 100 µm)were manufactured using astandard soft lithographyprocess and fitted into 3Dprinted inserts. In addition,devices (feature size: 0.5 mm –1.0 mm) were successfullyinjection moulded using 3Dprinted insert tooling.References1. Moore, T.A., Brodersen, P., Young, E.W.K., Anal. Chem. 2017; 89, 113912. M.W. Toepke, D.J. Beebe, Lab Chip 2006; 6, 1484.3. Y. Xia, G.M. Whitesides. Annu. Rev. Mater. Sci. 1998; 28, 153–1844. P.K. Challa, T. Kartanas, J. Charmet, T.P.J. Knowles, Biomicrofluidics 2017; 11, 0141135. H. Becker, C. Gärtner, Anal. Bioanal. Chem. 2008; 390, 89Three desirable material properties were selected,based on candidate device applications. Thesewere:• Optical transparency (High & Low)• Solvent Resistance (High)• Oxygen Permeability (High & Low)Fig 3 shows the plastic materials suitable for eachproperty combination. Materials in green have theadded benefit of chemically compatibility.CONCEPTTo evaluate the pattern replication achieved usingthis process, SEM images and surface profiles ofinjection moulded parts and PDMS inlays weremeasured using a Bruker Contour GTInterferometer, and then compared (Figs 6 to 9).Next steps are to:• Optimise process parameters for better featureresolution• Determine maximum lifetimes for differenttooling options• Trial smaller features sizes, and• Injection mould with different materials.Using standard process parameters, features with100 µm width and 50 µm depth were successfullyreplicated by injection moulding over PDMS micropatterned inlays in 3D printed inserts. Furtherprocess optimisation is required to achievereplication of features of 25 µm or below.3D printed insert tooling was also used to injectionmould devices with 0.5 mm – 1.0 mm feature sizes.Above, Figure 6: SEM micrograph ofinjection-moulded devices (PP) basedon PDMS inlay.Right, Figure 7: 3D surface profiles ofPDMS inlays before moulding over(TOP), after moulding over (BOTTOM),and the corresponding PP injectionmoulded device (CENTRE).Below, Figure 8: Surface profile crosssection of the radial feature shown inFigs 6 & 7.Figure 9: Mean profile dimensions of the radial feature shown in Figs 6 & 7.Figure 2: Concept diagram. Three key features of a required Organ on a Chip device determine an appropriate flexible, low-cost injection moulding prototyping strategy.Figure 3: A range of injection moulding thermoplastics covering combinations ofthe three selected desirable material properties.Figure 4: 3D Printed toolinsert with injection mouldand inlay cavities.Figure 5: Micro injectionmoulder.3D printed inserts (Fig 4)were designed with a fangates and side injectionpoints and fabricated usinga proprietary UV curingacrylic on a Stratasys J750Polyjet printer.Battenfeld 50 Microsystem(Fig 5) was used toinjection mould devices inpolypropylene (PP).

Low-cost injection moulding strategies for the fabrication of organ on a chip devices

http://wrap.warwick.ac.uk/110877/7/WRAP-BIWAOMEDENG18%20Low%20Cost%20Injection%20Moulding%20Strategies%20for%20Fabrication%20of%20Organ%20on%20a%20Chip%20Devices-Middleton-2018.pdf

Low-cost injection moulding strategies for the fabrication of organ on a chip devices

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