Plasma enhanced etching and chemical vapor deposition allow for the fabrication of superhydrophobic cellulose surfaces. Paper substrates with controlled surface properties can allow for precise control of liquid droplets.
Background: Lab-on-a-chip / microfluidic devices have experienced increased adoption in life sciences research and diagnostic applications. Paper-based microfluidic devices are promising because these devices are inexpensive and require much smaller fluid samples. Paper-based devices could lead to disposable diagnostics tests that are simple and abundant for use throughout the world.
Technology: Balamurali Balu, Victor Breedveld, and Dennis W. Hess from the School of Chemical and Biomolecular Engineering at Georgia Tech have demonstrated the fabrication of superhydrophobic paper/cellulose surfaces with tunability in adhesive forces by using a two-step plasma enhanced etching/chemical vapor deposition process. The tunability of the system enables flexibility of the surface from extremely sticky to non-sticky or “roll-off” superhydrophobicity. Patterns on paper substrates were designed and created using dots and lines printed by a desktop printer onto superhydrophobic sheets to create regions of variable adhesive force. Preliminary studies have demonstrated that superhydrophobic areas on non-sticky superhydrophobic surfaces can result in precise control and confinement of microliter water drops. The water drop adhesion/mobility can be controlled by varying the dot size and angle of inclination of the paper substrates. The two-dimensional nature of the paper substrate offers an alternative to three-dimensional channels commonly used in lab-on-a-chip / microfluidic devices.
Potential Commercial Applications: The paper substrates with controlled surface properties provide advantages for lab-on-a-chip / microfluidic devices in which individual drops can be manipulated on the surface, merged with other drops which may contain reactants, and stored on the surface as a final product for sampling. The most relevant market is the lab-on-a-chip market that is expected to increase to almost $9 billion annually by 2024.
Benefits / Advantages:
Enables tunability of adhesives forces on paper substrate to control liquid droplets
Provides an alternative to three-dimensional microfluidic channels
Inexpensive and easily fabricated from paper, a renewable biopolymer
Could lead to lab-on-a-chip / microfluidic devices used for diagnostic applications and/or life sciences research
Balamurali Balu- Former PhD student under Dr. Hess and Dr. Breedveld- Georgia Tech School of Chemical and Biomolecular Engineering
Laurens Victor Breedveld- Associate Chair for Undergraduate Studies, Associate Professor, and Frank Dennis Faculty Fellow- Georgia Tech School of Chemical and Biomolecular Engineering
Dennis W. Hess- Professor and Thomas C. DeLoach, Jr. Chair- School of Chemical and Biomolecular Engineering