3-dimensional electrode patterning within a microfluidic channel using metal ion implantation

Abstract

The application of electrical fields within a microfluidic channel enables many forms of manipulation necessary for lab-on-a-chip devices. Patterning electrodes inside the microfluidic channel generally requires multi-step optical lithography. Here, we utilize an ion-implantation process to pattern 3D electrodes within a fluidic channel made of polydimethylsiloxane (PDMS). Electrode structuring within the channel is achieved by ion implantation at a 40 angle with a metal shadow mask. The advantages of three-dimensional structuring of electrodes within a fluidic channel over traditional planar electrode designs are discussed. Two possible applications are presented: asymmetric particles can be aligned in any of the three axial dimensions with electro-orientation; colloidal focusing and concentration within a fluidic channel can be achieved through dielectrophoresis. Demonstrations are shown with E. coli, a rod shaped bacteria, and indicate the potential that ion-implanted microfluidic channels have for manipulations in the context of lab-on-a-chip devices.

Silicones for Microfluidic Systems

“…Th ey are fabricated with conventional lithography or sputtering and lift -off techniques. Electrodes can be deposited directly on PDMS molds using molten solder [44,144], metal ion implantation [145], conducting composites (carbon paste fi lling) [146] or singlewalled carbon nanotubes embedded in PDMS surface [147]. Optical components (fi bers, fi lters, photodiodes), important for on-chip detection, can be integrated into a microdevice during the molding step [148] or inserted into formed microchannels [17].…”

Controllable alignment of elongated microorganisms in 3D microspace using electrofluidic devices manufactured by hybrid femtosecond laser microfabrication

“…Thus, collecting enough data in a limited amount of time requires improvement in the efficiency of observing microorganism motions along a specific direction. Z-directional (perpendicular to the top and bottom surfaces of the microfluidic channel) electromanipulation is expected to improve the efficiency of front-view observation of continuously swimming microorganisms 17,19,32,46 . To this end, electrodes with a square outline (side length of outer square ≈1000 μm, side length of inner square (observation window) ≈500 μm, thus electrode width ≈250 μm), shown in Figure 4a, were prepared on the top and bottom of the interior walls of a microchannel (~1100 μm wide, 500 μm high) using hybrid fs laser microfabrication.…”

“…Flexible patterning of electrodes at any position in microfluidic channels provides more flexibility and extra functionality for electromanipulation in microfluidic environments 29 . Several approaches to fabricating and integrating electrodes with 3D configurations into microchannels have been attempted, primarily involving multiple lithographic steps combined with metal deposition and electroplating techniques 30,31 , metal ion implantation of a PDMS channel 32 , and in-channel injection of conductive liquid metals and composites [33][34][35] . The first two methods, however, require complex procedures involving the precise alignment and bonding of planar structures.…”

Exploitation of physical and chemical constraints for three-dimensional microtissue construction in microfluidics

“…These electrodes can be 2D, 63 3D, [64][65][66][67] a combination between a thin electrode and an extruded electrode, 68 or 3D DEP gates generated by placing the electrodes on top and at the bottom of the microfluidic channel. 69 Chang's group modulated the dielectrophoretic force that acts on different cells in a microfluidic device by buffer selection and cross-linking. 70,71 Lately, interdigitated comb electrodes have been used to generate gradients of an electrical field in a vertical direction; as a result, the cells can be trapped on the bottom of the microfluidic channel.…”