Droplet manipulations, including generating, splitting, transporting, and merging, play an important role in lab-on-a-chip (LOC) devices, also called micro total analysis systems (µTAS), which combine several laboratory functions on a single integrated circuit on scales of not more than a few square millimeters or centimeters. Due to their small size, LOC devices offer faster analysis and response times with low fluid volume consumption, low fabrication costs, better process control, and a compact system. The complex fluid operations network requires fine controls on miniscule scales. Traditionally, these droplet manipulations are performed using electrowetting-on-dielectric (EWOD) technology, in which a digital circuit is constructed using parallel plate channels. EWOD methods only work for conductive liquid droplets, limiting the range of usable liquids. Attempts to surpass this limitation involve using interdigitated electrodes, but these have been unable to carry out the necessary functions of transporting or splitting droplets. Thus there is an unmet need for LOC or µTAS devices that can carry out these droplet manipulations on small scales regardless of the conductivity of the liquid used.
Description
Researchers at the University of Pittsburgh have invented a new electrode design that can drive microdroplets in digital microfluidics. The novel, microfluidic device working in half-open space described here vastly improves upon current EWOD technology. Key features include individually addressable electrode arrays that allow users to drive conductive or non-conductive droplets to perform the required droplet operations on a planar chip. A non-uniform electric field generated by the interdigital electrodes penetrates the droplet and alters the contact angle in a specific direction. The corresponding electro-hydro force is much stronger than that in EWOD and can be used on conductive as well as non-conductive liquid. Additionally, this new electrode design enables droplet splitting without a top cover glass and works with AC as well as DC signals, opening up new potential applications and allowing for improved design flexibility.
Applications
· At-home pregnancy test kits
· Low-cost flow cytometers to diagnose and manage HIV infections
· Automated monitoring of volatile organic compounds for homeowner safety and homeland security
· Other low cost, point-of-care diagnostic tools, especially for use in underfunded, under-developed health clinics and labs
Advantages
· Can be used on both conductive and non-conductive liquid while maintaining a full range of droplet manipulations
· Electro-hydro force is much stronger compared to traditional technology
· Can be used without a top cover glass
· Works with AC as well as DC signals
Invention Readiness
Prototype
IP Status
https://patents.google.com/patent/US20230158504A1
