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, Professor Lim Chwee Teck and team presented an alternative solution for the rapid prototyping of microfluidic elements such as microtubes, valves, and pumps. In addition, they demonstrated how microtubes with channels of various lengths and cross-sections can be attached modularly into 2D and 3D microfluidic systems for functional applications.

A facile method of fabricating elastomeric microtubes is introduced 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.

Their 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.

The schematic showing the diverse applications of the microtubes in various domains: from microparticles/cells separation and droplet generation using physical force fields, to micromotor actuation using biocatalytic reactions, to triboelectric sensing using electrochemical principles, and finally to wearable sensing using physicoelectrical phenomenon.

The research paper has been published in PNAS | vol. 114 no. 40 vol. 10590–10595, doi: 10.1073/ pnas.1712195114 doi: 10.1073/pnas.1712195114

Wearable electronics have gained dramatic development in recent years, owing to the advancement in flexible/
stretchable electronics, and achieved considerable progress in various applications. Nanogenerators capable of
harvesting energy from human activities is considered as a promising alternative for powering the wearable
electronic devices, considering the sustainability and rich biomechanical energy from human body. Currently,
most of the nanogenerators are aimed at converting limited forms of mechanical energy, mostly pressing or
bending, which hampers adaptive exploitation of bodily energy source. Also, the incapability to respond to
multiple forms of mechanical stimuli deters the nanogenerators from functioning as full-range human activities
sensors. Here, we devise a stretchable integrated nanogenerator-sensory coaxial core-sheath fiber with improved
functionality and sustainability. The combination of materials engineering and structure design enables the fiber
to scavenge versatile mechanical energy, including stretch, bend, twist and press, through a gap size variation
induced electrostatic effect. Besides, the fiber realizes the detection of joint-bending and joint-twisting related
motions, such as walking and elbow rotation, and also succeeds in capturing subtle physiological signals, such as
breath, pulse and speech recognition, which paves the way for full-range personal healthcare monitoring and
documenting in a self-powered, wearable and noninvasive manner.

Researcher / Author: Yin Cheng, Xin Lu, Kwok Hoe Chan, Ranran Wang, Zherui Cao, Jing Sun, Ghim Wei Ho

Nano Energy 41 (2017) 511–518; http://dx.doi.org/10.1016/j.nanoen.2017.10.010