Abstract
Microfluidics has become a very promising technology in recent years, due to its great potential to revolutionize life-science solutions. Generic microfabrication processes have been progressively made available to academic laboratories thanks to cost-effective soft-lithography techniques and enabled important progress in applications like lab-on-chip platforms using rapid- prototyping. However, micron-sized features are required in most designs, especially in biomimetic cell culture platforms, imposing elevated costs of production associated with lithography and limiting the use of such devices. In most cases, however, only a small portion of the structures require high-resolution and cost may be decreased. In this work, we present a replica-molding method separating the fabrication steps of low (macro) and high (micro) resolutions and then merging the two scales in a single chip. The method consists of fabricating the largest possible area in inexpensive macromolds using simple techniques such as plastics micromilling, laser microfabrication, or even by shrinking printed polystyrene sheets. The microfeatures were made on a separated mold or onto existing macromolds using photolithography or 2-photon lithography. By limiting the expensive area to the essential, the time and cost of fabrication can be reduced. Polydimethylsiloxane (PDMS) microfluidic chips were successfully fabricated from the constructed molds and tested to validate our micro–macro method.
Highlights
Microtechnology has contributed greatly to the progress of society thanks to the incredible growth of electronics that it has permitted
Photolithography has been the central process enabling fast miniaturization of individual components and complex layouts with metal, oxides and semiconductors required in circuit integration
The cost associated with fabricating large areas on resist patterns transferred onto the mold substrates for subsequent replicas in PDMS is not ideal, as these common structures shared by all microfluidic chips usually do not require high-resolution processes with a very high associated cost per area. and different strategies may be employed nowadays [12]
Summary
Microtechnology has contributed greatly to the progress of society thanks to the incredible growth of electronics that it has permitted. The cost of materials and infrastructure required by this technology has always been relatively elevated, the high integration levels enabled by this technology have decreased the overall cost per chip This said, when different construction materials such as polymers are required, or if small-volume rapid-prototyping devices are sought, microtechnology remains too expensive for many laboratories, especially in low-resource universities or developing countries. Usually photoresists are used to transfer patterns onto a wafer or a glass slide using a photomask, that needs to be fabricated and usually presents a high associated cost that is not suitable for testing and prototyping Other maskless techniques such as 2-photon lithography guarantee high resolutions but their cost per area and processing time are too high for large surfaces (Table 1). Large-scale structures have been manufactured using the 2-photon technique, there are still area limits and there is a need to use micromanipulators to make the connections with tubings and external pumps, which with our method may not be necessary [16]
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