Soft tubular microfluidics for 2D and 3D applications
- aCentre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546;
- bMechanobiology Institute, National University of Singapore, Singapore 117411;
- cSingapore-Massachusetts Institute of Technology Alliance of Research and Technology, National University of Singapore, Singapore 117548;
- dDepartment of Biomedical Engineering, National University of Singapore, Singapore 117583;
- eNational University of Singapore Graduate School of Integrative Sciences and Engineering, National University of Singapore, Singapore 117456;
- fMinistry of Education Key Laboratory of Hydrodynamics, Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
- gSJTU-CU (Shanghai Jiao Tong University-Chiba University) International Cooperative Research Center, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
- hCollaborative Innovation Center for Advanced Ship and Deep Sea Exploration, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved August 28, 2017 (received for review July 15, 2017)

Significance
The current cleanroom-based soft lithography microfabrication process is complicated and expensive. There is a need for low-cost, ready-to-use, modular components that can be easily assembled into microfluidic devices by users lacking proficiency or access to microfabrication facilities. We present a facile, low-cost, and efficient method of fabricating soft, elastic microtubes with different cross-sectional shapes and dimensions. These microtubes can be used as basic building blocks for the rapid construction of various 2D and 3D microfluidic devices with complex geometries, topologies, and functions. This approach avoids the conventional cumbersome photolithography process and thus, provides a feasible way for scaling up the production of microfluidic devices.
Abstract
Microfluidics has been the key component for many applications, including biomedical devices, chemical processors, microactuators, and even wearable devices. This technology relies on soft lithography fabrication which requires cleanroom facilities. Although popular, this method is expensive and labor-intensive. Furthermore, current conventional microfluidic chips precludes reconfiguration, making reiterations in design very time-consuming and costly. To address these intrinsic drawbacks of microfabrication, we present an alternative solution for the rapid prototyping of microfluidic elements such as microtubes, valves, and pumps. In addition, we demonstrate how microtubes with channels of various lengths and cross-sections can be attached modularly into 2D and 3D microfluidic systems for functional applications. We introduce a facile method of fabricating elastomeric microtubes as the basic building blocks for microfluidic devices. These microtubes are transparent, biocompatible, highly deformable, and customizable to various sizes and cross-sectional geometries. By configuring the microtubes into deterministic geometry, we enable rapid, low-cost formation of microfluidic assemblies without compromising their precision and functionality. We demonstrate configurable 2D and 3D microfluidic systems for applications in different domains. These include microparticle sorting, microdroplet generation, biocatalytic micromotor, triboelectric sensor, and even wearable sensing. Our approach, termed soft tubular microfluidics, provides a simple, cheaper, and faster solution for users lacking proficiency and access to cleanroom facilities to design and rapidly construct microfluidic devices for their various applications and needs.
- flexible microfluidics
- elastomeric microtubes
- microfluidic assemblies
- inertial focusing chip
- microfluidic sensor
Footnotes
↵1W.X., F.K., and J.C.Y. contributed equally to this work.
- ↵2To whom correspondence may be addressed. Email: x.gong{at}sjtu.edu.cn or ctlim{at}nus.edu.sg.
Author contributions: W.X., J.C.Y., X.G., and C.T.L. designed research; W.X., F.K., J.C.Y., L.Y., S.S., and X.G. performed research; M.D. and C.T.L. contributed new reagents/analytic tools; W.X. and F.K. analyzed data; W.X., J.C.Y., and C.T.L. wrote the paper; W.X., F.K., J.C.Y., and L.Y. made the figures; M.D. contributed useful ideas; and X.G. and C.T.L. supervised research.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1712195114/-/DCSupplemental.