Safe and cost-effective rapid-prototyping of multilayer PMMA microfluidic devices

Antonio Liga,Maïwenn Kersaudy-Kerhoas,Jonathan A S Morton

doi:10.1007/s10404-016-1823-1

Antonio Liga, Maïwenn Kersaudy-Kerhoas + Show 1 more

Open Access

https://doi.org/10.1007/s10404-016-1823-1

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Abstract

The rapid translation of research from bench to bedside, as well as the generation of commercial impact, has never been more important for both academic and industrial researchers. It is therefore unsurprising that more and more microfluidic groups are investigating research using a wide range of thermoplastics which can be readily translated to large-scale manufacturing, if the technology is taken to commercialisation. While structuring, via additive or subtractive manufacturing, is becoming relatively easy through the use of commercial-grade devices, reliable and fast assembly remains a challenge. In this article, we propose an innocuous and cost-effective, under 2-min technique which enables the bonding of multiple poly(methyl methacrylate) layers. This bonding technique relies on the application of small amounts (10 µl/cm2) of ethanol, low temperatures (70 °C) and relatively low pressures (~1.6 MPa). Our characterisation analysis shows that using a bonding time of 2 min is enough to produce a strong bond able to withstand pressures always above 6.2 MPa (with mean of 8 MPa, highest reported in the literature), with minimal channel deformation (<5%). This technique, which we demonstrate on assembly comprising up to 19 layers, presents an exciting improvement in the field of rapid prototyping of microfluidic devices, enabling extremely fast design cycles in microfluidic research with a material compatible with mass manufacturing, thus allowing a smoother transition from the laboratory to the market. Beyond the research community, this robust prototyping technique has the potential to impact on the deliverability of other scientific endeavours including educational projects and will directly fuel the fluidic maker movement.

Highlights

Due to its low cost, optical transparency and the availability of a range of processing methods, poly(methyl methacrylate) (PMMA) has been adopted for many microfluidic applications (Das et al 2015; Pagaduan et al 2015)
We show a bonding method that allows for the fast, cost-effective and safe bonding of multilayer stacks of PMMA, overtaking part of the barrier that prevents the translation of microfluidics from the laboratory to the real world
The most common PMMA bonding technique is thermal bonding, in which PMMA elements are heated above the glass transition temperature [Tg ranging from 85 °C to 165 °C depending on the commercial composition (Duan et al 2010) but usually around 110 °C (Li et al 2015)] and pressed together

Summary

Introduction

Due to its low cost, optical transparency and the availability of a range of processing methods, poly(methyl methacrylate) (PMMA) has been adopted for many microfluidic applications (Das et al 2015; Pagaduan et al 2015). Variants of the aforementioned solutions include the use of UV light to activate surfaces (Tran et al 2013), microwave heating combined with a conductive layer [patterned gold (Toossi et al 2015), conductive polymer (Holmes et al 2011) or metal clips acting on a solvent layer (Mona et al 2010)], or plasma treatment (Cheng et al 2015), which can be optimised to reach a bonding strength of 0.57 MPa in 20 min (Zhifu et al 2015) These procedures are time-consuming and require specialist equipment (Lin et al 2007). A fast PMMA prototyping methodology, developed by Sun et al (2007), consists of a solvent-based imprinting and bonding strategy This method allows for the realisation of PMMA chips in 15 min; it requires the use of photolithography techniques for the realisation of a template for the imprinting in a photoresist material, commonly SU8. Using layers of a lower Tg polymer, such as TMMF (photosensitive epoxy laminate) for the thermal welding of PMMA, reduces deformation on the PMMA bulk, the procedure is time-consuming and requires photolithography equipment for the shaping of TMMF (Kalkandjiev et al 2010)

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