Droplet microfluidic device and methods of sensing the result of an assay therein

An assay measurement system for determining a result of an assay, the assay measurement system comprising:

• a microfluidic device including an electrode array configured to receive fluid droplets;
• a controller configured to control actuation voltages applied to the electrode array to perform manipulation operations to the fluid droplets;
• and
• a plurality of sensors for sensing a dynamic property of the fluid droplets as a result of the manipulation operations:
• wherein:
• a sample droplet is dispensed onto a first portion of the electrode array;
• a reagent droplet is dispensed onto a second portion of the electrode array;
• the controller controls actuation voltages applied to the electrode array to mix the sample droplet and the reagent droplet into a product droplet;
• a dynamic property is a physical property of the product droplet that influences droplet transport on the microfluidic device, and a chemistry of the assay being performed is chosen such that the product droplet has the dynamic property depending on the result of the assay being performed;
• the controller is configured to control actuation voltages applied to the product droplet to affect a droplet transport operation at a first position on the electrode array on the microfluidic device;
• the plurality of sensors includes a first sensor that senses the product droplet at the first position;
• the plurality of sensors includes a second sensor that senses the product droplet at a second position on the electrode array on the microfluidic device different from the first position;
• the controller is configured to execute application software to automatically determine the sensed dynamic property based on a result of the droplet transport operation using transport measurements sensed by the first and second sensors;
• and
• the controller is configured to execute application software to automatically determine the result of the assay of the sample droplet directly from the sensed dynamic property by equating either a positive or negative result for a target species in the sample droplet to the result of the transport operation.

A method of determining a result of an assay in an active matrix electrowetting on dielectric (AM-EWOD) microfluidic device comprising the steps of:

• dispensing a sample droplet from a sample reservoir onto a first portion of an electrode array of the microfluidic device;
• dispensing a reagent droplet from a reagent reservoir onto a second portion of the electrode array of the microfluidic device;
• controlling actuation voltages applied to the electrode array of the microfluidic device to mix the sample droplet and the reagent droplet into a product droplet;
• sensing a dynamic property of the product droplet, wherein a dynamic property is a physical property of the product droplet that influences droplet transport on the microfluidic device, and the dynamic property depends on the result of the assay being performed;
• wherein sensing the dynamic property includes the steps of:
• controlling actuation voltages applied to the product droplet to affect a droplet transport operation at a first position on the electrode array on the microfluidic device, and sensing the product droplet with a first sensor at the first position;
• sensing the product droplet with a second sensor at a second position on the electrode array on the microfluidic device different from the first position;
• and
• executing application software with control electronics to automatically determine the sensed dynamic property based on a result of the droplet transport operation using transport measurements sensed by the first and second sensors;
• and
• executing application software with the control electronics to automatically determine the result of the assay of the sample droplet directly from the sensed dynamic property by equating either a positive or negative result for a target species in the sample droplet to the result of the transport operation;
• wherein the transport property of the product droplet is related to a viscosity of the product droplet;
• and
• the method further comprises actuating a portion of the electrode array associated with the product droplet to split the product droplet into daughter droplets, wherein the viscosity of the droplet is determined based on sensing a distance between centroids of the daughter droplets at a time of splitting of the product droplet by actuation of the electrode array portion.