Abstract: A method may include maintaining a sample comprising an ionic species and an optical indicator at an elevated temperature above 25° C. on a semi-conductive microfluidic die during an incubation period, intermittently interrogating the sample with an interrogating light during the incubation period and sensing a response of the sample to the interrogating light, wherein the sample is interrogated with the interrogating light only during those times at which the sample is being sensed.

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 controller outputs control signals controlling a frequency source to selectively apply different nonzero frequencies of alternating current at different times to an electric sensor within a microfluidic channel.

Abstract: A fluid testing system comprises controlling hardware that serves to control an electric sensor on a fluid testing cassette. In one implementation, the controlling hardware is part of a cassette interface. In another implementation, the controlling hardware is part of the portable electronic device. In one implementation, the fluid testing system applies two different frequencies of alternating current are applied to two different electric sensors.

Abstract: A microfluidic diagnostic chip may comprise a main fluid channel comprising a main pump, a secondary fluid channel branching off from the main fluid channel, and a secondary pump within the secondary fluid channel wherein the secondary pump is to pull a particle of analyte of a first size from a fluid passing through the main channel, the fluid comprising particles of analyte of the first size and of a number of larger sizes. A method of analyzing an analyte on a microfluidic chip may comprise pumping, with a main microfluidic pump, a fluid comprising an analyte particle through a main microfluidic channel fluidly coupled to a fluid slot and sorting the analyte particle within the fluid through a secondary microfluidic channel by pulling the analyte particle into the secondary microfluidic channel with a secondary microfluidic pump.

Abstract: The present disclosure includes a description of an example print bar that includes an ejection die disposed on a support element, and a sensor disposed at a particular location on the support element.

Abstract: A microfluidic diagnostic device may comprise a fluid inlet to receive a fluid from a fluidic slot, a main microfluidic channel fluidly coupled to the fluid inlet, and a main microfluidic pump interposed between the fluid inlet and the main microfluidic channel to continuously circulate a fluid through the fluidic slot, fluid inlet, and main microfluidic channel wherein the width of the fluid inlet is different from the width of the main microfluidic channel. A diagnostic device, comprising a fluidic slot, a fluid inlet fluidly coupled to the fluidic slot, a main channel fluidly coupled to the fluid inlet, and an inlet pump interposed between the fluid inlet and channel wherein the cross-sectional area of the fluid inlet is relatively larger at least one point than the cross-sectional area of the channel.

Abstract: A thin film stack can include a metal substrate having a thickness of from 200 angstroms to 5000 angstroms and a passivation barrier disposed on the metal substrate at a thickness of from 600 angstroms to 1650 angstroms. The passivation barrier can include a dielectric layer and an atomic layer deposition (ALD) layer disposed on the dielectric layer. The dielectric layer can have a thickness of from 550 to 950 angstroms. The ALD layer can have a thickness from 50 to 700 angstroms.

Abstract: A microfluidic sensing device comprises a channel and an impedance sensor within the channel. The impedance sensor comprises a local ground and an electrode within the channel. The local ground and the electrode are to form an electric field region that is elongated along the channel.

Abstract: The present disclosure includes a description of an example print bar that includes an ejection die disposed on a support element, and a sensor disposed at a particular location on the support element.

Abstract: An apparatus includes a microfluidic passage, a chamber, an inlet connecting the microfluidic passage to the chamber, a sensor proximate the inlet to sense fluid within the inlet, a first nozzle, a first fluid driver to move fluid through the first nozzle to draw fluid across the inlet, a second nozzle, a second fluid driver to move fluid through the second nozzle to draw fluid across the inlet and a controller. The controller sequentially actuates the first fluid driver and the second fluid driver.

Abstract: Vented microfluidic reservoirs can include a housing and a vent coupled to the housing to vent air associated with a fluid sample communicated into the housing to an environment surrounding a microfluidic device coupled to the housing.

Abstract: A microfluidic diagnostic device may comprise a fluid inlet to receive a fluid from a fluidic slot, a main microfluidic channel fluidly coupled to the fluid inlet, and a main microfluidic pump interposed between the fluid inlet and the main microfluidic channel to continuously circulate a fluid through the fluidic slot, fluid inlet, and main microfluidic channel wherein the width of the fluid inlet is different from the width of the main microfluidic channel. A diagnostic device, comprising a fluidic slot, a fluid inlet fluidly coupled to the fluidic slot, a main channel fluidly coupled to the fluid inlet, and an inlet pump interposed between the fluid inlet and channel wherein the cross-sectional area of the fluid inlet is relatively larger at least one point than the cross-sectional area of the channel.

Abstract: A device includes a microfluidic channel structure on a substrate with a first fluid actuator and a second fluid actuator within the microfluidic channel structure. One of the fluid actuators is selectively employable to at least partially reverse fluid flow within at least a portion of the microfluidic channel structure in response to a blockage or to prevent a blockage.

Abstract: A microfluidic diagnostic chip may comprise a main fluid channel comprising a main pump, a secondary fluid channel branching off from the main fluid channel, and a secondary pump within the secondary fluid channel wherein the secondary pump is to pull a particle of analyte of a first size from a fluid passing through the main channel, the fluid comprising particles of analyte of the first size and of a number of larger sizes. A method of analyzing an analyte on a microfluidic chip may comprise pumping, with a main microfluidic pump, a fluid comprising an analyte particle through a main microfluidic channel fluidly coupled to a fluid slot and sorting the analyte particle within the fluid through a secondary microfluidic channel by pulling the analyte particle into the secondary microfluidic channel with a secondary microfluidic pump.

Abstract: A method of microfluidic detection can include detecting, using an impedance sensor, an impedance of a fluid to indicate whether a threshold amount of fluid has been received in a reservoir of a microfluidic chip. The method can include initiating a test performed by the microfluidic chip on the received fluid when the threshold amount of fluid has been received.

Abstract: A device including a microfluidic channel structure formed on a substrate and including a first channel and a fluid actuator within the microfluidic channel structure. A sense region within the first channel is to receive a fluid flow of target biologic particles for counting in a single file pattern, with the sense region having a volume on a same order of magnitude as a volume of a single one of the target biologic particles.

Abstract: A microfluidic diagnostic chip may comprise a microfluidic channel, a functionalizable enzymatic sensor in the microfluidic channel, the functionalizable enzymatic sensor comprising a binding surface to bind with a biomarker in a fluid, and a microfluidic pump to pass the fluid over the binding surface.

Abstract: A printhead includes a plurality of firing chambers, a plurality of fluid ejectors, and at least one field generating member. Each one of the firing chambers includes a nozzle region to receive printing fluid. The printing fluid includes an ink vehicle having pigments disposed therein. At least one field generating member generates a non-uniform electric field to apply forces to maintain respective pigments in the ink vehicle of the printing fluid in the nozzle region.

Abstract: Example implementations relate to coagulation sensing. For example, a microfluidic chip for coagulation sensing may include a microfluidic channel, an outlet at an end of the microfluidic channel having an air interface, and an impedance sensor located within the microfluidic channel and within a particular proximity to the air interface, the impedance sensor to determine a stage of a coagulation cascade of a blood sample flowing through the microfluidic channel to the impedance sensor.