From lab to fab - Roll to Roll replication ofmicrostructures in to PDMS
Olli-Heikki Huttunen 1,2 , Johanna H. Hiitola-Keinänen, 1,2 Tuomas Happonen,1,3Jussi K. Hiltunen 1Sensing and Integration 1, Printed Electronics Processing 2, Flexible Electronics Integration3
VTT Technical Research Centre of Finland
Kaitoväylä 1, 90570 Oulu, FinlandE-mail: olli-heikki.huttunen@vtt.fi,

Polydimethyl siloxane (PDMS) has been already two decades extremely important materialfor prototyping microfluidics for biomedical research. [1] Still recently, related mass
production of PDMS devices has been considered difficult and for example roll processing
even impossible.[1]Very recently, we have developed Roll-to-Roll replication process and demonstratedfunctionality of such microfluidic components by performing nucleic acid amplification inroll-to roll replicated device. [2] The molds for replication process were in house madephotoresist master molds attached on hot embossing cylinder. We have found photoresist
molds to be sufficient for prototyping purpose. For production, durable metal molds can beused. In replication we used two component room temperature vulcanizing silicone
elastomer (Wacker Elastosil RT604) and aluminized paper substrate (Zanders Chromolux).[2]Web speed in replication was 1,5 m min-1 which equals 9 m2 h-1 with 100 mm wide web.
With standard microscope slide sized devices (25 mm × 75 mm) total area equals 4800
devices in an hour. The same machine is also capable to operate with 200 mm wide web,which doubles the throughput.
We have also demonstrated rotary screen printed silver conductor traces on PDMS substrates,
which enables combination of PDMS microfluidics with many electrical functions.
Electrochemical sensors are commonly used in diagnostics. [3] Conductive traces are manytimes essential for signal and power transportation for other sensor devices. We usedcommercial silver paste (from Creative Materials) and substrates (Elastosil film ™, fromWacker Chemie).
Microfluidics market size was eastimated for US$ 10 billion for 2018 and subject to reach
US$28billion by 2023.[4] We believe there is constantly increasing number of highly
potential PDMS based microfluidic applications developed in academy whose developers arelooking opportunities to also develop business from their research. One option is to transformand redevelop the device physics and chemistries to meet existing mass manufacturing
techniques such as injection molding. Another approach is to upscale manufacturing ofexisting prototypes. Our approach is to develop upscaled manufacturing process for
microstructures and for that we using roll to roll techniques. VTT operates open accessresearch infra structure for printed electronics, including two roll to roll pilot level machines
equipped with embossing/imprinting units capable also on PDMS processing.
VTT leads Printocent community which is based on 3 research partners, city of Oulu and over
30 industry cluster partners. Purpose of Printocent is gather whole value chain and ecosystem
together and boost industrialization and commercialization of printed electronics.

References:[1] Sackmann, E.K., Fulton, A. L, Beebe D.J., “The present and future role of microfluidics
in biomedical research”, Nature, 2014, 507, 181.
[2] Hiltunen J., Liedert C., Hiltunen M., Huttunen O.-H., Hiitola-Keinänen J., Aikio S.,Harjanne M., Kurkinen M., Hakalahti L. and Lee L. P, “Roll-to-roll fabrication of
integrated PDMS–paper microfluidics for nucleic acid amplification,” Lab Chip, 2018,18,1552-1559[3] Banks C.E., Killard T., and Venton B. J., “Introduction to electrochemistry for healthapplications”, Anal. Methods, 2019, 11, 2736-2737[4]https://www.marketsandmarkets.com/Market-Reports/microfluidics-market-1305.html

Replicatedmicrofluidics

Web rewind

Pattern replication
PDMS coating
Al-coated paper

Figure 1 Roll to roll replication of PDMS [2]Figure 2 a) Roll of
replicated PDMS fluidics onaluminized paper in width of100mm.
b)RNA
amplification
device filled with blue andred color [2]