Dielectric layers for digital microfluidic devices
Inventors
Visani, Cristina • Paolini, Jr., Richard J.
Assignees
Publication Number
US-12128411-B2
Publication Date
2024-10-29
Expiration Date
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
An electrowetting system is disclosed. The system includes electrodes configured to manipulate droplets of fluid in a microfluidic space. Each electrode is coupled to circuitry operative to selectively apply a driving voltage to the electrode. The system includes a dielectric stack including a first dielectric pair comprising a first layer having a first dielectric constant and a second layer having a second dielectric constant. The second dielectric constant is larger than the first dielectric constant. The dielectric stack includes a second dielectric pair comprising a third layer having a third dielectric constant and a fourth layer having a fourth dielectric constant. The fourth dielectric constant is larger than the third dielectric constant. A ratio of a thickness of the fourth layer to a thickness of the third layer (T4:T3) is in the range from about 2:1 to about 8:1. The second dielectric pair is thinner than the first dielectric pair.
Core Innovation
An electrowetting system is disclosed that includes electrodes configured to manipulate droplets of fluid in a microfluidic space, wherein each electrode is coupled to circuitry operative to selectively apply a driving voltage to the electrode, and a dielectric stack comprising a first dielectric pair (a first layer having a first dielectric constant and a second layer having a second dielectric constant, the second dielectric constant larger than the first) and a second dielectric pair (a third layer having a third dielectric constant and a fourth layer having a fourth dielectric constant, the fourth dielectric constant larger than the third), wherein a ratio T4:T3 is in the range from about 2:1 to about 8:1 and the second dielectric pair is thinner than the first dielectric pair.
The patent addresses electrochemical degradation of dielectric layer stacks in digital microfluidic (DMF) devices caused by continuous actuation of droplets, noting that protecting devices against electrochemical degradation with thick dielectric layers leads to very high actuation potentials in segmented devices and that high voltage operation beyond about ±30 V is apt to damage TFT circuitry used in active matrix EWoD devices.
The disclosure provides multi-layer dielectric stacks combining one or more low dielectric constant layers for protection against electrical breakdown with one or more high dielectric constant layers for improving performance, describes alternating layers of low-k and high-k materials to minimize pinhole formation, and teaches that manufacturing may use high-quality deposition techniques such as atomic layer deposition (ALD) or higher-output methods to strike an optimal balance between expected results and operating expenses.
Claims Coverage
The patent contains two independent claims and five main inventive features.
Electrode array with selective driving circuitry
A plurality of electrodes configured to manipulate droplets of fluid in a microfluidic space, wherein each electrode is coupled to circuitry operative to selectively apply a driving voltage to the electrode.
First dielectric pair with higher-k second layer
A first dielectric pair comprising a first layer having a first dielectric constant and a second layer having a second dielectric constant, wherein the second dielectric constant is larger than the first dielectric constant.
Second dielectric pair with specified thickness ratio and thinner overall thickness
A second dielectric pair comprising a third layer having a third dielectric constant and a fourth layer having a fourth dielectric constant, wherein the fourth dielectric constant is larger than the third dielectric constant; a ratio T4:T3 is in the range from about 2:1 to about 8:1, wherein T3 is a thickness of the third layer and T4 is a thickness of the fourth layer; and the total thickness of the second dielectric pair is thinner than the total thickness of the first dielectric pair.
Dielectric stack comprising a first dielectric layer and a thin dielectric pair
A dielectric stack comprising a first dielectric layer having a first dielectric constant, and a thin dielectric pair comprising a second dielectric layer and a third dielectric layer, wherein the third dielectric layer has a dielectric constant greater than the second dielectric layer, a ratio TH:TL is in the range from about 3:1 to about 8:1 (TH a thickness of the third layer, TL a thickness of the second layer), and the dielectric pair is thinner than the first dielectric layer.
Third dielectric layer higher-k relative to second dielectric layer with specified ratio
The thin dielectric pair wherein the third dielectric layer has a dielectric constant greater than the second dielectric layer and the ratio TH:TL is in the range from about 3:1 to about 8:1.
Independent claims recite an electrowetting system with an electrode array coupled to selective driving circuitry and multi-layer dielectric stacks characterized by dielectric pairs where a higher-k layer is paired with a lower-k layer, with specified layer thickness ratios (e.g., T4:T3 about 2:1 to 8:1 or TH:TL about 3:1 to 8:1) and thinner additional dielectric pairs compared to a thicker first dielectric pair.
Stated Advantages
Combines high performance with resistance to electrochemical degradation.
Minimizes the likelihood of pinholes forming throughout the entire thickness of the stack.
Provides an optimized balance between expected results and operating expenses (strikes an optimal balance between expected results and operating expenses).
Enables lower actuation voltages by using thin high-k dielectric layers to improve performance while protecting against degradation.
Documented Applications
Lab-on-a-chip uses including sample preparation, assays, and synthetic chemistry performed with tiny quantities of samples and reagents.
Droplet operations including loading a droplet, dispensing droplets from a source reservoir, splitting, separating or dividing droplets, moving droplets, merging or combining droplets, diluting, mixing, agitating, deforming, holding, incubating, heating, vaporizing, cooling, disposing of, and transporting droplets.
Use in biochemical protocols including a reagent for a biochemical protocol, a nucleic acid amplification protocol, an affinity-based assay protocol, an enzymatic assay protocol, a gene sequencing protocol, and a protein sequencing protocol.
Analysis and handling of biological samples and biological fluids including whole blood, serum, plasma, saliva, sputum, cerebrospinal fluid, amniotic fluid, urine, fecal samples, liquids containing single or multiple cells, and related biological reagents.
Chemical synthesis applications including reagents for synthesizing oligonucleotides and reagents for peptide and protein production.
Use in active matrix EWoD (AM-EWoD) devices and TFT-based DMF devices to enable many thousands to millions of addressable electrodes for mass parallelization of droplet procedures.
Interested in licensing this patent?