Abstract: The present disclosure is drawn to microfluidic devices. A microfluidic device can include a substrate, a lid mounted to the substrate, and a microchip mounted to the substrate. The lid mounted to the substrate can form a discrete microfluidic chamber between structures including an interior surface of the lid and a portion of the substrate. The lid can include an inlet and a vent positioned relative to one another to facilitate loading of fluid to the discrete microfluidic chamber via capillary action. A portion of the microchip can be positioned within the discrete microfluidic chamber.

Abstract: The present disclosure is drawn to microfluidic devices. The microfluidic device includes a microfluidic well, a layered composite stack, and an optical sensor. The layered composite stack includes an optical filter composited with an etch-stopping layer. The optical filter defines the microfluidic well. The optical sensor is associated with the microfluidic well and has the optical filter positioned therebetween.

Abstract: The present disclosure is drawn to microfluidic devices. The microfluidic device includes a substrate, an optically translucent lid, an adhesive securing the substrate to the lid, and an optical barrier material between the substrate and the optically translucent lid.

Abstract: An example device includes a processor to connect to an electrode disposed within a microfluidic volume and to connect a second electrode that includes a surface of silver metal disposed within the microfluidic volume. The processor is to apply an electrical potential between the electrode and the second electrode when the microfluidic volume contains a fluid that contains chloride ions to form a layer of silver chloride on the surface of the second electrode. The processor is further to cease application of the electrical potential and operate the second electrode as a reference electrode in a measurement process performed within the microfluidic volume.

Abstract: In one example in accordance with the present disclosure, a fluid analysis device is described. The device includes a substrate, a die adhered to the substrate, and at least one fluid analysis element disposed on the die. A lid is adhered to the substrate and includes a channel formed thereinto be seated over the die. The device also includes an inlet port to the channel and an outlet from the channel. The inlet port and the outlet port are formed on at least one of the substrate and the lid. A number of electrical traces couple the die to a controller.

Abstract: In one example in accordance with the present disclosure, a fluid analysis device is described. The fluid analysis device includes a chamber to receive a number of fluids. At least one fluid includes an electrochemical label with a unique electrochemical response to an applied electrical potential. A multi-electrode sensor of the fluid analysis device is disposed within the chamber and detects electrical signals within the chamber. The fluid analysis device also includes a controller coupled to the multi-electrode sensor. The controller applies an electrical potential across multiple electrodes of the multi-electrode sensor and identifies, from the electrical signal detected by the multi-electrode sensor, fluids currently in the chamber based on the unique electrochemical responses of associated electrochemical labels.

Abstract: The present disclosure is drawn to microfluidic chips. The microfluidic chips can include an inflexible material having an elastic modulus of 0.1 gigapascals (GPa) to 450 GPa. A microfluidic channel can be formed within the inflexible material and can connect an inlet and an outlet. A working electrode can be associated with the microfluidic channel and can have a surface area of 1 ?m2 to 60,000 ?m2 within the microfluidic channel. A bubble support structure can also be formed within the microfluidic channel such that the working electrode is positioned to electrolytically generate a bubble that becomes associated with the bubble support structure.

Abstract: According to an example, a microfluidic apparatus may include a fluid slot and a foyer that is in fluid communication with the fluid slot via a channel having a relatively smaller width than the foyer. The microfluidic apparatus may also include an electrical sensor to measure a change in an electrical field caused by a particle of interest in a fluid passing through the channel from the fluid slot to the foyer, an actuator to apply pressure onto fluid contained in the foyer, and a controller to receive the measured change in the electrical field from the electrical sensor, determine, from the received change in the electrical field, an electrical signature of the particle of interest, and control the actuator to control movement of the particle of interest based upon the determined electrical signature of the particle of interest.

Abstract: An example device includes a processor to connect to an electrode disposed within a microfluidic volume and to connect a second electrode that includes a surface of silver metal disposed within the microfluidic volume. The processor is to apply an electrical potential between the electrode and the second electrode when the microfluidic volume contains a fluid that contains chloride ions to form a layer of silver chloride on the surface of the second electrode. The processor is further to cease application of the electrical potential and operate the second electrode as a reference electrode in a measurement process performed within the microfluidic volume.

Abstract: The present disclosure is drawn to microfluidic devices. A microfluidic device can include a substrate, a lid mounted to the substrate, and a microchip mounted to the substrate. The lid mounted to the substrate can form a discrete microfluidic chamber between structures including an interior surface of the lid and a portion of the substrate. The lid can include an inlet and a vent positioned relative to one another to facilitate loading of fluid to the discrete microfluidic chamber via capillary action. A portion of the microchip can be positioned within the discrete microfluidic chamber.

Abstract: The present disclosure is drawn to microfluidic chips. The microfluidic chips can include an inflexible material having an elastic modulus of 0.1 gigapascals (GPa) to 450 GPa. A microfluidic channel can be formed within the inflexible material and can connect an inlet and an outlet. A working electrode can be associated with the microfluidic channel and can have a surface area of 1 ?m2 to 60,000 ?m2 within the microfluidic channel. A bubble support structure can also be formed within the microfluidic channel such that the working electrode is positioned to electrolytically generate a bubble that becomes associated with the bubble support structure.

Abstract: A microfluidic blood coagulation testing die includes a substrate, a slot in the substrate permitting entry of a sample of blood, a chamber in the substrate for collection of cells in the sample, and a pinch point that permits passage of sample from slot to chamber. The die includes a sensor in or near the at least one pinch point to test sample passing through the at least one pinch point. Activator, such as freeze-dried coagulation-initializing tissue factor, coats at least a portion of the interior surface of the slot, pinch point, and chamber.

Abstract: A microfluidic blood coagulation testing die includes a substrate, a slot defined in the substrate permitting entry of a blood sample, a chamber defined in the substrate that collects red blood cells from the blood sample, and a microfluidic path that provides a fluid connection from the slot to the chamber. The microfluidic path includes a channel, an inlet disposed at one end of the channel and an outlet disposed at the other end of the channel.

Abstract: According to an example, a microfluidic apparatus may include a fluid slot and a foyer that is in fluid communication with the fluid slot via a channel having a relatively smaller width than the foyer. The microfluidic apparatus may also include an electrical sensor to measure a change in an electrical field caused by a particle of interest in a fluid passing through the channel from the fluid slot to the foyer, an actuator to apply pressure onto fluid contained in the foyer, and a controller to receive the measured change in the electrical field from the electrical sensor, determine, from the received change in the electrical field, an electrical signature of the particle of interest, and control the actuator to control movement of the particle of interest based upon the determined electrical signature of the particle of interest.

Abstract: An electrode system and a method of using an electrode system to make an impedance measurement. The electrode system comprises a substrate that supports a first and second electrodes. The first electrode is located inside a cutout of the second electrode. The first and second electrodes are separated by an insulating layer.