Kota Research Group

 

Surface science deals with the study of physical and chemical phenomena occurring at the interface of two or more phases. The strength of our research lies both in understanding the surface physics and the ability to tune the surface chemistry to develop advanced materials with engineered surface properties. The advanced materials developed in our work address some of the key issues in the areas of membrane separations, phase change heat transfer, icephobicity, droplet fluid mechanics, open channel microfluidics, microrobots, hemocompatibility and sensors. Checkout our YouTube channel - https://www.youtube.com/channel/UCvEIKTsJkaK9kEqw5cSm6Bw

Superomniphobic Surfaces

Surfaces that are extremely repellent to water are known as superhydrophobic surfaces; surfaces that are extremely repellent to low surface tension liquids, such as oils and alcohols, are known as superoleophobic surfaces. Superomniphobic surfaces display both superhydrophobicity and superoleophobicity. More specifically, superomniphobic surfaces display contact angles greater than 150o and a very low contact angle hysteresis (difference between advancing and receding contact angles).
Superomniphobic surfaces can be designed by fabricating re-entrant textured surfaces with low surface energy that can support the contacting liquid in the Cassie-Baxter state.


With the above understanding, in our work {Pan et al. J. Am. Chem. Soc. (2013); Kota et al. Adv. Mater. (2012)}, we developed hierarchically structured (finer length scale texture on an underlying coarser length scale texture) superomniphobic surfaces, which display ultra-low contact angle hysteresis (less than 4o) for virtually all Newtonian and non-Newtonian liquids. Consequently, concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces.


We envision that our superomniphobic surfaces will have numerous applications including stain-free clothing and spill-resistant, breathable protective wear, enhanced solvent resistance, biofouling resistant surfaces, self-cleaning, drag reducing, and lightweight corrosion-resistant coatings.


Our current efforts are focused on improving the mechanical durability of our superomniphobic surfaces.

 

Open Channel Microfluidics & Sensors

Open channel microfluidics focuses on manipulating small amounts of liquid on surfaces to develop diagnostic devices and sensors etc.
Recently, manipulation of liquid droplets on super-repellent surfaces (i.e., surfaces that are extremely repellent to liquids) has been widely studied because droplets exhibit high mobility on these surfaces due to the ultra-low adhesion, which leads to minimal sample loss and contamination.


In our work {Movafaghi et al. Lab Chip (2016)}, we designed a simple sensor that enables droplet sorting based on surface tension. We fabricated a superomniphobic surface on titanium and tuned the surface energy of individual domains on the surface using UV irradiation. Leveraging different roll off angles in different surface energy domains, we demonstrate droplets adhering in specific domains based on their surface tension.


We anticipate our methodology for droplet sorting will enable inexpensive and energy-efficient analytical devices for personalized point-of-care diagnostic platforms, lab-on-a-chip systems, biochemical assays and biosensors.


Our current efforts are focused on developing multifunctional open channel microfluidic devices and sensors.

 

Hemocompatible Surfaces

Hemocompatible surfaces are surfaces that are compatible with blood. Typically, blood platelets do not adhere and activate significantly on
such surfaces. Consequently, such surfaces offer a potential solution for reducing blood clotting and infection due to blood-contacting medical implants such as stents, catheters etc.


In our work {Movafaghi et al. Adv. Healthc. Mater. (2016)}, we investigated the blood platelet adhesion and activation on superhemophobic titania surfaces (i.e., surface that are extremely repellent to blood). Our results indicate that superhemophobic surfaces with a robust Cassie-Baxter state display very low platelet adhesion and activation.


We envision that our superhemophobic surfaces will pave the way to blood-contacting medical implants with improved hemocompatibility.


Our current efforts are focused on better understanding the hemocompatibility of our superhemophobic surfaces.

 

Deicing Surfaces

Adhesion and build-up of ice on exposed surfaces (e.g., airplanes, ships, power lines, automobiles, oil drilling marine structures) can be a severe
hazard and even endanger human life. Deicing surfaces allow easy removal of ice due to their low ice adhesion strength (i.e., the critical shear stress required to separate ice from the surface). Deicing surfaces with ultra-low ice adhesion strength and good mechanical durability are highly desirable.


In our work {Beemer et al. J. Mater. Chem. A. (2016)}, building on the principles of adhesion mechanics, we developed novel inexpensive, environmentally benign, non-corrosive PDMS gels that offer ultra-low adhesion to ice as well as outstanding mechanical durability. We elucidated the mechanism of separation of ice from our PDMS gels via separation pulses.


We envision that our durable PDMS gels with ultra-low ice adhesion strength as well as the improved understanding of the separation mechanism will enable universal deicing design strategies in aviation, maritime, power, automotive, and energy sectors.


Our current efforts are focused on better understanding the adhesion of ice to PDMS gels.