Laser micromachined hybrid open/paper microfluidic chips

Abstract

Paper-based microfluidics are an increasingly popular alternative to devices with conventional open channel geometries. The low cost of fabrication and the absence of external instrumentation needed to drive paper microchannels make them especially well suited for medical diagnostics in resource-limited settings. Despite the advantages of paper microfluidics, many assays performed using conventional open channel microfluidics are challenging to translate onto paper, such as bead, emulsion, and cell-based assays. To overcome this challenge, we have developed a hybrid open-channel/paper channel microfluidic device. In this design, wick-driven paper channels control the flow rates within conventional microfluidics. We fabricate these hybrid chips using laser-micromachined polymer sheets and filter paper. In contrast to previous efforts that utilized external, macroscopic paperbased pumps, we integrated micro-scale paper and open channels onto a single chip to control multiple open channels and control complex laminar flow-pattern within individual channels. We demonstrated that flow patterns within the open channels can be quantitatively controlled by modulating the geometry of the paper channels, and that these flow rates agree with Darcy's law. The utility of these hybrid chips, for applications such as bead-, cell-, or emulsion-based assays, was demonstrated by constructing a hybrid chip that hydrodynamically focused micrometer-sized polystyrene beads stably for >10 min, as well as cells, without external instrumentation to drive fluid flow. V C 2013 AIP Publishing LLC.

Modular pumps as programmable hydraulic batteries for microfluidic devices

“…Capillary pumps have been fabricated via photolithography within microfl uidic devices to pull fl uids through microchannels [8][9][10] , but their integration within the device prevents exchanging or replacing the pumps. To lower the cost and fabrication time of capillary pumps, several groups have used paper connected to the distal end of a microfl uidic channel to pull fl uid [11][12][13][14] . Th ese paper pumps use simple geometric shapes to generate a single fl ow rate but they only work on channels with relatively low fl uidic resistances and are built into the analytical test substrate.…”

A magnetic micropore chip for rapid (<1 hour) unbiased circulating tumor cell isolation and in situ RNA analysis

“…The device is pretreated with Pluronic F-127 (Sigma–Aldrich) to minimize nonspecific retention of cells to the channel walls or to the TEMPO. Because the device does not require accurately controlled flow rates, it is well suited for mobile use where flow can be driven by inexpensive pumps or capillary action 30,31 .…”

Microfluidic Time-Delay Valve Mechanism on Paper-Based Devices for Automated Competitive ELISA

“…Various time-delay valve mechanisms have been developed to achieve sequential fluid flow deliveries by assigning different time delays to plural channels, which are formed by hydrophobic materials (e.g., wax) in geometrical patterns [14][15][16][17], on hydrophilic papers. Common examples are actuators [18][19][20][21], physical barriers [22][23][24][25][26][27], and chemical substances [28,29]. While they are all effective approaches, actuators require external force, and physical barriers may cause damage to paper-based devices.…”