Editing Lab-on-a-chip (section)

== Chip materials and fabrication technologies ==
The basis for most LOC fabrication processes is [[photolithography]]. Initially most processes were in silicon, as these well-developed technologies were directly derived from [[semiconductor]] fabrication. Because of demands for e.g. specific optical characteristics, bio- or chemical compatibility, lower production costs and faster prototyping, new processes have been developed such as glass, ceramics and metal [[industrial etching|etching]], deposition and bonding, [[polydimethylsiloxane]] (PDMS) processing (e.g., [[soft lithography]]), [[Off-stoichiometry thiol-ene polymer]]s (OSTEmer) processing, thick-film- and [[stereolithography]]-based 3D printing<ref>{{cite journal |last1=Gonzalez |first1=Gustavo |last2=Chiappone |first2=Annalisa |last3=Dietlikee |first3=Kurt |last4=Pirri |first4=Fabrizio |last5=Roppolo |first5=Ignazio |title=Fabrication and Functionalization of 3D Printed Polydimethylsiloxane-Based Microfluidic Devices Obtained through Digital Light Processing |journal=Advanced Materials Technologies |date=2020 |volume=5 |issue=9 |page=2000374 |doi=10.1002/admt.202000374 |s2cid=225360332 |url=https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/admt.202000374|url-access=subscription }}</ref> as well as fast replication methods via [[electroplating]], [[injection molding]] and [[Embossing (manufacturing)|embossing]]. The demand for cheap and easy LOC prototyping resulted in a simple methodology for the fabrication of PDMS microfluidic devices: ESCARGOT (Embedded SCAffold RemovinG Open Technology).<ref>{{cite journal |author1=Saggiomo, V. |author2=Velders, H. A. | title = Simple 3D Printed Scaffold-Removal Method for the Fabrication of Intricate Microfluidic Devices | journal = Advanced Science | volume = 2 | issue = 8 | pages = X |date=Jul 2015 | doi = 10.1002/advs.201500125 |pmid=27709002 | pmc = 5115388 }}</ref> This technique allows for the creation of microfluidic channels, in a single block of PDMS, via a dissolvable scaffold (made by e.g. [[3D printing]]).<ref>{{cite web|url=https://www.youtube.com/watch?v=7z8I7awRYY4 |archive-url=https://ghostarchive.org/varchive/youtube/20211222/7z8I7awRYY4 |archive-date=2021-12-22 |url-status=live|title=Simple fabrication of complex microfluidic devices (ESCARGOT)|author=Vittorio Saggiomo|date=17 July 2015|via=YouTube}}{{cbignore}}</ref>
Furthermore, the LOC field more and more exceeds the borders between lithography-based microsystem technology, nanotechnology and precision engineering. Printing is considered as a well-established yet maturing method for rapid prototyping in chip fabrication.<ref>{{cite journal | vauthors = Loo J, Ho A, Turner A, Mak WC | title = Integrated Printed Microfluidic Biosensors | journal = Trends in Biotechnology | volume = 37 | issue = 10 | pages = 1104–1120 | date = 2019 | pmid = 30992149 | doi = 10.1016/j.tibtech.2019.03.009 | hdl = 1826/15985 | s2cid = 119536401 | url = http://dspace.lib.cranfield.ac.uk/handle/1826/15985 }}</ref>

The development of LOC devices using [[printed circuit board]] (PCB) substrates is an interesting alternative due to these differentiating characteristics: commercially available substrates with integrated electronics, sensors and actuators; disposable devices at low cost, and very high potential of commercialization.<ref>{{Cite journal |last=Moschou |first=Despina |year=2017 |title=The lab-on-PCB approach: tackling the μTAS commercial upscaling bottleneck |journal=Lab on a Chip |volume=17 |issue=8 |pages=1388–1405 |doi=10.1039/C7LC00121E |pmc= |pmid= 28294256|doi-access=free}}</ref> These devices are known as Lab-on-PCBs (LOPCBs).<ref>{{Cite journal|last=Perdigones|first=Francisco|title=Lab-on-PCB and Flow Driving: A Critical Review|journal=[[Micromachines]]|year=2021|volume=12|issue=2|pages=175|doi=10.3390/mi12020175|pmid=33578984|pmc=7916810|doi-access=free}}</ref> The following are some of the advantages of PCB technology:
a) PCB-based circuit design offers great flexibility and can be tailored to specific demands.<ref>{{cite journal | doi = 10.1002/elps.201900444 | title = The review of Lab-on-PCB for biomedical application | year = 2020 | last1 = Zhao | first1 = Wenhao | last2 = Tian | first2 = Shulin | last3 = Huang | first3 = Lei | last4 = Liu | first4 = Ke | last5 = Dong | first5 = Lijuan | journal = Electrophoresis | volume = 41 | issue = 16–17 | pages = 1433–1445 | pmid = 31945803 | s2cid = 210699552 }}</ref>
b) PCB technology enables the integration of electronic and sensing modules on the same platform, reducing device size while maintaining accuracy of detection.
c) The standardized and established PCB manufacturing process allows for cost-effective large-scale production of PCB-based detection devices.
d) The growth of flexible PCB technology has driven the development of wearable detection devices. As a result, over the past decade, there have been numerous reports on the application of Lab-on-PCB to various biomedical fields, including the fastest SARS-CoV-2 molecular diagnostic test.<ref>{{Cite journal |last1=Papamatthaiou |first1=Sotirios |last2=Boxall-Clasby |first2=James |last3=Douglas |first3=Edward J. A. |last4=Jajesniak |first4=Pawel |last5=Peyret |first5=Hadrien |last6=Mercer-Chalmers |first6=June |last7=Kumar |first7=Varun K. S. |last8=Lomonossoff |first8=George P. |last9=Reboud |first9=Julien |last10=Laabei |first10=Maisem |last11=Cooper |first11=Jonathan M. |last12=Kasprzyk-Hordern |first12=Barbara |last13=Moschou |first13=Despina |date=2023 |title=LoCKAmp: lab-on-PCB technology for |journal=Lab on a Chip |language=en |volume=23 |issue=20 |pages=4400–4412 |doi=10.1039/D3LC00441D |issn=1473-0197 |pmc=10563828 |pmid=37740394}}</ref>
e) PCBs are compatible with wet deposition methods, to allow for the fabrication of sensors using novel nanomaterials (e.g. graphene).<ref>{{cite journal | doi = 10.1039/d2nr05838c | title = A sprayed graphene transistor platform for rapid and low-cost chemical sensing | year = 2023 | last1 = Fenech-Salerno | first1 = Benji | last2 = Holicky | first2 = Martin | last3 = Yao | first3 = Chengning | last4 = Cass | first4 = Anthony E. G. | last5 = Torrisi | first5 = Felice | journal = Nanoscale | volume = 15 | issue = 7 | pages = 3243–3254 | pmid = 36723120 | s2cid = 256261782 | hdl = 10044/1/102808 | hdl-access = free }}</ref><ref>{{Cite journal |last1=Papamatthaiou |first1=Sotirios |last2=Estrela |first2=Pedro |last3=Moschou |first3=Despina |date=2021-05-10 |title=Printable graphene BioFETs for DNA quantification in Lab-on-PCB microsystems |journal=Scientific Reports |language=en |volume=11 |issue=1 |pages=9815 |doi=10.1038/s41598-021-89367-1 |issn=2045-2322 |pmc=8111018 |pmid=33972649|bibcode=2021NatSR..11.9815P }}</ref>