Page 40 - IJB-2-1

Utilising inkjet printed paraffin wax for cell patterning applications

that are essential in the understanding of fabricating inherent in these techniques can be reduced, from
microdevices to control cell-substrate interactions [9–12] . around 24 hours (with the majority of this time being
The importance of such research was highlighted in a used for mould preparation), to hours.
special themed issue of Soft Matter in 2014 on cells in With respect to inkjet printing for cell guidance,
patterned environments [13] . Being able to control the this typically involves depositing a biologically active
deposition and location of cells onto a surface allows molecule such as fibronectin, collagen and/or poly-
the creation of scaffolds suitable for tissue engineering, mers, to selectively adhere cells at specific places on a
biosensors, the formation of neuronal networks, cell- substrate [21,22] . The use of wax for the creation of mi-
based assays and for the study of cell-cell interactions. crofluidic devices has been used to create paper and
The current “gold standard” for preparing patterned glass-based devices as a simple and inexpensive me-
environments for cells uses PDMS (polydimethylsi- thod using commercially available materials [23–25] .
loxane) during the construction of lab-on-a-chip de- This ability to create biosensors has been investigated
vices and micropatterning [14] . With the ability to mod- to an extent with inkjet printing technology [26–29] .
ify mechanical, optical and chemical properties, pat- In this paper we have described for first time inkjet
terning on glass [15] or silicon [16] , PDMS is a versatile printing paraffin wax on tissue culture plastic and on a
material. An essential requirement when using PDMS plain glass substrate and these formed structures were
is the creation of a master mould, into which PDMS then used to guide cell attachment, spreading and pro-
can be poured, cured and removed to create the de- liferation, without further processing steps. Previous
sired construct. There has been research in reducing research using paraffin wax for the creation of micro-
and making the process easier, as the pattern design fluidic devices described wax deposition integrated
can be created on the master mould through soft-litho- with paper, film or combined with PDMS stam-
graphy, or through etching into silicon. The photo- ping [30–33] . The current approach for cell patterning
mask can be created using high resolution printers [15] involves creating the desired pattern by CAD software
or photo-plotters [17] , but a clean room environment is (Figure 1A), bypassing the need to create a master
required for fabrication. Solid object printers have been mould or use of PDMS, and thereafter the immediate
used to create the initial patterns for the master seeding of cells after fabrication (Figure 1B). The in-
mould [18] , with resolutions of >250 µm. Other tech- kjet printing system was able to move through three
niques have also been investigated by researchers,
which deposit a cell attractive or repelling agent onto
a substrate, with cells thereafter physically restrained
to grow within the confines [19,20] . Such approaches,
however, do not allow the user to remove such a
physical confine at a later time.
The use of PDMS is advantageous if several copies
of the master pattern are required. However, when the
user requires a large range of variances in their design
during prototyping, a typical need exists to create tens,
or even hundreds of master moulds. In contrast, the
direct patterning of a design using wax printed on a
substrate bypasses the conventional process of using
PDMS. Potential applications of our proposed method
are found in the field of simulation studies and opti-
mising microdevice prototypes [6,21] .
Using inkjet printing to produce patterned envi-
ronments offers fewer limitations compared to pre-
viously mentioned techniques that use UV exposure,
photomasks and organic and toxic solvents, and re-
quire long processing times, complicated machinery, Figure 1. (A) Wax was printed in the desired micrometre scale

etching and multiple steps. Avoiding these drawbacks shape on a substrate; (B) cells were seeded onto the substrate
would aid in the fabrication of microfluidic devices in and left to attach, spread and proliferate; (C) when required, the
research and industry settings, as the turnaround times wax could be physically removed, to leave the cells in situ.

36 International Journal of Bioprinting (2016)–Volume 2, Issue 1