Abstract: A fluid ejection die may include a fluid actuator, a substrate supporting the fluid actuator, a chamber layer supported by the substrate and a bypass passage in the substrate. The substrate may include a closed inlet channel having an inlet opening for connection to an outlet of a fluid source and an outlet channel having an outlet opening of a first size for connection to an inlet of the fluid source. The chamber layer includes a recirculation passage to supply fluid for ejection by the fluid actuator through an ejection orifice and to circulate fluid across the fluid actuator from the closed inlet channel to the outlet channel. The bypass passage is of a second size less than the first size and connects the inlet channel to the inlet of the fluid source while bypassing any fluid actuator provided for ejecting fluid through an ejection orifice.

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: A diagnostic cassette includes a substrate, to physically and electrically connect the product to a computing device, a reservoir defined within the substrate to receive a fluid sample for processing by the diagnostic cassette, a reagent to react with the fluid sample deposited in the reservoir to form a solution to enable processing of the fluid sample by the diagnostic cassette, a channel to direct the solution, and a sensor to measure a number of parameters of the solution passing through the channel. A method for measuring microfluidic samples includes receiving, in a reservoir, a fluid sample to be measured, combining the fluid sample with a reagent to create a solution, moving the solution through a channel, and measuring the solution, using sensors, as the solution passes through the channel.

Abstract: In some examples, a fluid system includes a support structure to attach a fluid dispensing device comprising a fluid chamber to contain a fluid, and an orifice to dispense the fluid from the fluid chamber. The fluid system includes a circulation path comprising a path portion in the fluid dispensing device, the circulation path to circulate a fluid flow through the fluid chamber to remove, from the fluid chamber, a particle ingested through the orifice. A filter in the circulation path is to remove the particle from the circulation path.

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 fluidic die may include a fluid channel layer defining a number of fluid channels therein, a slot layer disposed on a side of the fluid channel layer, and a first fluid slot and a second fluid slot defined in the slot layer. At least one of the fluid channels fluidically couples the first fluid slot to the second fluid slot. The first fluid slot and the second fluid slot are defined in the slot layer along a length of the fluidic die.

Abstract: A fluidic die may include a fluid channel layer defining a number of fluid channels therein, a slot layer disposed on a side of the fluid channel layer, and a first fluid slot and a second fluid slot defined in the slot layer. At least one of the fluid channels fluidically couples the first fluid slot to the second fluid slot. The first fluid slot and the second fluid slot are defined in the slot layer along a length of the fluidic die.

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 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 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: 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 fluidic die may include a at least one actuator, and fluid flow architecture to flow a first fluid through at least one fluidic channel, and flow a second fluid through the at least one fluidic channel to form a laminar flow between the first fluid and the actuator. The at least one actuator forms a drive bubble from the second fluid to cause the first fluid to be ejected from the fluidic die.

Abstract: A system may comprise a voltage upconverter, a universal serial bus (USB) connector to receive an input voltage from a USB port on a computing device, and a microfluidic diagnostic chip communication link to electrically couple the voltage upconverter to a microfluidic diagnostic chip wherein the voltage upconverter is to convert the input voltage to be received by the USB connector to an output voltage sufficient to drive a pump on the microfluidic diagnostic chip. A diagnostic system may comprise a microfluidic diagnostic chip comprising a pump and a voltage upconverter to receive an input voltage from a universal serial bus (USB) port of a computing device and to convert the input voltage into an output voltage that powers activation of the pump.

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. A microfluidic device may comprise a number of pumps to pump a fluid though the number of microfluidic channels and a number of microfluidic channels comprising at least one sensor to detect a change in a chemical characteristic of the fluid in response to presence of the fluid on the sensor.

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 fluidic die may include a fluid channel layer defining a number of fluid channels therein, a slot layer disposed on a side of the fluid channel layer, and a first fluid slot and a second fluid slot defined in the slot layer. At least one of the fluid channels fluidically couples the first fluid slot to the second fluid slot. The first fluid slot and the second fluid slot are defined in the slot layer along a length of the fluidic die.

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.

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.