Development of a 3D Graphene Electrode Dielectrophoretic Device

Summary

A microdevice with high throughput potential is used to demonstrate three-dimensional (3D) dielectrophoresis (DEP) with novel materials. Graphene nanoplatelet paper and double sided tape were alternately stacked; a 700 μm micro-well was drilled transverse to the layers. DEP behavior of polystyrene beads was demonstrated in the micro-well.

Abstract

The design and fabrication of a novel 3D electrode microdevice using 50 µm thick graphene paper and 100 µm double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 µm x 0.7 cm x 2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 μm diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 μm polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete.

Introduction

Graphene is a novel material known for its high quality electronic properties and potential chemical and biosensor applications¹. Graphene nanoplatelets have been used for catalyst support^2,3, biosensors⁴, super-capacitors⁵, and composite-electrodes including graphene/polyaniline and silicon nanoparticle/graphene composites^6-8. This manuscript describes utilization of graphene paper as electrodes in a unique three-dimensional (3D), layered microfluidic device. Graphene paper electrodes were laminated with insulative double-sided tape and a chamber drilled within which 3D AC dielectrophoresis ....

Protocol

1. Fabricate a Laminated Electrode/insulation 3D Structure

1. For a 6 graphene layer, 5 tape layer device, cut graphene paper with a scalpel or similar razor blade and straight-edged ruler into six 0.7 cm x 1.5 cm rectangles and use scissors to cut double-sided pressure-sensitive tape into five 1.3 cm x ~5 cm stripes.
   NOTE: As shown in Figure 1a, this yields a 3 ground electrode, 3 AC signal electrode device. The 7 mm conducting layer width is narrow enough to fit onto a glass slide, yet wide enough for easy drilling. The 2 mm length does not easily break upon repeated use and has sufficient room to attach copper wires. The device depth ....

Results

Dielectrophoretic experiments on 6 µm polystyrene beads were conducted in a 0.38 mm³ cylindrical micro-well. Results demonstrate that a 3D laminated graphene paper-based device can illustrate similar dielectrophoretic signatures as 3D metal foil laminated devices^20,21, traditional 2D metal-electrode^26,27, and 2D insulator devices²⁵. In the following experiments, an 15 V_peak-peak AC signal was applied and frequency was varie.......

Discussion

This manuscript details protocols for fabricating a novel 6 graphene layer and 5 tape layer microdevice. Further, device operation is illustrated via observed DEP behaviors of 6.08 µm polystyrene beads along with a unique, geometrically relevant particle velocity analysis approach. This versatile approach to construct nonlinear electrokinetic devices is less costly than electrode and fluidic layer microfabrication techniques, while yielding equally reliable results.

Further, this novel 3D.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Polystyrene Beads	Spherotech, Inc.	PP-60-10	6.08 μm diameter
Graphene paper	XG Sciences, Inc.	XG Leaf B-072
Double sided tape	3M	N/A	136 office tape
Silver conductive epoxy	MG chemicals	8331-14G	Part A & B included
Mannitol	Sigma Aldrich	091M0020V
Phosphate buffer saline	OmniPur	0381C490
Microscope (CCD Camera)	Zeiss	Axiovert 200M
Function/waveform generator	Agilent	33250A
Syringe	Hamilton	84505
Paper Clamp	ADAMS	3300-50-3848
Oven	Fisher Scientific	280A
Multimeter	OMEGA	HHM25
Micro-milling machine	AEROTECH	ABL1500 stages/A3200 Npaq controller
End mill	ULTRATOOL	708473
AxioVision	Zeiss	Version 4.8