Using Adhesive Patterning to Construct 3D Paper Microfluidic Devices

Summary

We demonstrate the use of patterned aerosol adhesives to construct 3D paper microfluidic devices. This method of adhesive application forms semi-permanent bonds between layers, enabling single-use devices to be non-destructively disassembled after use and to ease folding complex nonplanar structures.

Abstract

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol adhesive through a metal stencil, the overall amount of adhesive used in assembling paper microfluidic devices can be significantly reduced. We show on a simple 4-layer planar paper microfluidic device that the optimal adhesive application technique and device construction style depends heavily on desired performance characteristics. By moderately increasing the overall area of a device, it is possible to dramatically decrease the wicking time and increase device success rates while also reducing the amount of adhesive required to keep the device together. Such adhesive application also causes the adhesive to form semi-permanent bonds instead of permanent bonds between paper layers, enabling single-use devices to be non-destructively disassembled after use. Nonplanar 3D origami devices also benefit from the semi-permanent bonds during folding, as it reduces the likelihood that unrelated faces may accidently stick together. Like planar devices, nonplanar structures see reduced wicking times with patterned adhesive application vs uniformly applied adhesive.

Introduction

In recent years, paper microfluidics has garnered considerable popularity for its potential to provide low-cost point of care (POC) diagnostic devices.^1-3 POC devices offer functionality similar to those of lab-based tests in a format that allows results to be obtained relatively quickly. POC devices made from paper are low-cost, lightweight, and easy-to-use alternatives to expensive microfluidic chips and miniaturized laboratories, making them ideal for use in resource-limited settings. The most common paper microfluidic devices are one-dimensional lateral flow devices, but planar three-dimensional (3D) paper microfluidic devices hold promise to provide mu....

Protocol

1. Planar 4-layer Device (Stacked Layers) Construction

1. Print arrays of each layer of the device⁹ onto each piece of filter paper using a solid ink printer.^11,12 Place each filter paper on a hotplate at 170 °C for 2 min. This will melt the wax-based ink and allow it to fully penetrate the thickness of the paper, forming hydrophobic barriers.
   NOTE: The exact designs used are available as supplemental files.
2. Remove filter paper from hotplate and allow it to cool to RT.
3. Deposit 4 µl of 5 mM dye (red: Allura Red; yellow: tartrazine; blue: erioglaucine disodium salt; green: 10:1 mix of tartrazine:eriogla....

Results

The 4-layer device tests were performed in a sealed chamber, shielding them from any wind or breezes that might cause excessive evaporation of the limited deposited fluid volume. The majority of the wicking in the 4-layer devices is in the middle layers of the device, so differences in wicking speeds due to evaporation were expected to be minimal. Additionally, there is minimal lateral wicking, with only 13 mm between the inlet and any individual outlet, suggesting that variations in wick.......

Discussion

The above protocols use perforated metal sheets as stencils for applying aerosol adhesives to construct planar and nonplanar 3D paper microfluidic devices. In planar devices, this has the advantage of allowing devices to be completely unfolded after the adhesive has dried without destroying the device. In other adhesive based construction techniques, this is almost impossible, although, some designs allow for partial destructive disassembly by unpeeling two halves held together with a removable adhesive.¹⁴ Adh.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Camera	Nikon	D5100
Solid-ink printer	Xerox	ColorQube 8880
Hotplate	Torrey Pines	HS60
Humidity chamber	Electro-Tech Systems	5503-E
Spray adhesive	3M	62497749309	Super 77 (16.75 oz can)
Filter paper	Whatman	Grade 4
Perforated steel sheet	MetalsDepot	PS16116
Tartrazine	Sigma-Aldritch	T0388
Allura Red	Sigma-Aldritch	458848
Erioglaucine disodium salt	Sigma-Aldritch	861146