Abstract: An example device includes a microfluidic channel and a movable element retained in the microfluidic channel to move from a first position to a second position by fluid flow through the microfluidic channel. The device includes a sensor to take a sensor reading to determine fluid flow through the microfluidic channel. The device includes a microfluidic pump to return the movable element from the second position to the first position. The device includes a controller to actuate the microfluidic pump and to determine a flow rate of the fluid flow through the microfluidic channel based on the sensor reading.

Abstract: Examples include microfluidic devices. Example microfluidic devices include a first microfluidic channel, a second microfluidic channel, and a third microfluidic channel fluidly coupled to the first microfluidic channel and the second microfluidic channel via a fluid junction. A fluid actuator is disposed in the third microfluidic channel to actuate to thereby pump a first fluid and a second fluid into the third microfluidic channel.

Abstract: The present disclosure is drawn to microfluidic devices. In one example, a microfluidic device can include a first covered fluid feed slot in fluid communication with a first microfluidic channel and a second covered fluid feed slot in fluid communication with a second microfluidic channel. The first microfluidic channel can be formed adjacent to the second microfluidic channel but not in fluid communication with the second microfluidic channel. The first covered fluid feed slot can include a first fluid feed hole for filling a fluid into the first covered fluid feed slot. The second covered fluid feed slot can also include a second fluid feed hole for filling a fluid into the second covered fluid feed slot.

Abstract: An apparatus may include a first microfluidic valve coupled between a first reservoir and a fluid channel. The first microfluidic valve may include a fluid agitator to break a meniscus formed at an air-fluid interface and release fluid from the first reservoir into the fluid channel in response to an electrical signal. The apparatus may also include a second microfluidic valve coupled between a second reservoir and the fluid channel. Fluid from the first reservoir and fluid from the second reservoir mix in the fluid channel.

Abstract: An example device includes a first droplet ejector including a first nozzle to eject droplets of a first fluid, and a first target medium positioned relative to the first droplet ejector to receive the droplets of the first fluid from the first droplet ejector. The example device further includes a second droplet ejector in fluid communication with the first target medium to receive a second fluid from the first target medium. The second droplet ejector includes a second nozzle to eject droplets of the second fluid.

Abstract: One example includes a device that may include a heating element and a molecular binding site. The heating element may heat a fluid volume, interfaced with the heating element, in response to a voltage being applied to the heating element, the heat transforming the fluid volume from a liquid state into a vaporized state to generate fluid motion within the fluid volume. The molecular binding site may be disposed proximate to the heating element, in which a portion of the fluid volume expands when the fluid volume transforms from the liquid state into the vaporized state, the vaporized state of the fluid volume generating the fluid motion within a target fluid that is disposed within the molecular binding site.

Abstract: Examples herein involve cell lysis with a microbead and thermal resistor. An example apparatus includes a microfluidic channel to pass a volume including a microbead and a biologic sample having nucleic acids enclosed within a cellular membrane. A first thermal resistor may be disposed within the microfluidic channel to move the biologic sample through the microfluidic channel and lyse the cellular membranes in the biologic sample to release the nucleic acids. A microfilter disposed within the microfluidic channel may filter the microbead from the biologic sample and permit the nucleic acids to pass through the filter.

Abstract: An example device includes a first substrate including a first array of droplet ejectors to eject droplets of a first fluid. The example device further includes a first target medium immovably positioned relative to the first substrate to receive droplets of the first fluid from a first subset of droplet ejectors of the first array of droplet ejectors. A second subset of droplet ejectors of the first array of droplet ejectors is positioned to eject droplets of the first fluid to miss the first target medium.

Abstract: Example fluidic channels for microfluidic devices are disclosed. In examples disclosed herein, an example microfluidic device includes a body having a microfluidic network. The microfluidic network includes a main fluid channel to transport a biological fluid from a first cavity of the microfluidic network to a second cavity of the microfluidic network. An auxiliary fluid channel is in fluid communication with to the main fluid channel. The auxiliary fluid channel has a first end and a second end. The first end is in fluid communication with the main fluid channel and the second end is spaced from the main fluid channel. A fluid actuator is positioned in the auxiliary fluid channel to induce fluid flow in the main fluid channel.

Abstract: A microfluidic device may include a first fluid chamber, a second fluid chamber, a first microfluidic passage extending between the first fluid chamber and the second fluid chamber, a second microfluidic passage extending from the second fluid chamber, a first fluid actuator adjacent the first microfluidic passage and proximate the first fluid chamber to inertially pump fluid away from the first fluid chamber and a second fluid actuator adjacent the first microfluidic passage and proximate the second fluid chamber to menially pump fluid towards the first fluid chamber.

Abstract: An example system includes an input channel having a first end and a second end to receive particles through the first end, a separation chamber, at least two output channels, and an integrated pump to facilitate flow through the separation chamber. The separation chamber is in fluid communication with the second end of the input channel. The separation chamber has a passive separation structure, the passive separation structure including an array of columns spaced apart to facilitate separation of particles in a flow based on a size of the particles. Each output channel is in fluid communication with the separation chamber to receive separated particles. The integrated pump is positioned within at least one of the input channel or one of the at least two output channels.

Abstract: A microfluidic valve comprises a first reservoir, a second reservoir, an inertial pump and a channel connecting the first reservoir to the second reservoir. The second reservoir is to receive fluid from the first reservoir through the channel under a pressure gradient. The inertial pump is within the channel proximate the second reservoir and distant the first reservoir.

Abstract: An example device includes a first substrate including a first array of droplet ejectors to eject droplets of a first fluid. The example device further includes a first target medium immovably positioned relative to the first substrate to receive droplets of the first fluid from a first subset of droplet ejectors of the first array of droplet ejectors. A second subset of droplet ejectors of the first array of droplet ejectors is positioned to eject droplets of the first fluid to miss the first target medium.

Abstract: An example device includes a droplet ejector including a nozzle to eject droplets of a fluid and a target medium to receive the droplets of the fluid. The target medium is separated from the droplet ejector by a gap to be traversed by the droplets. The example device further includes a frame affixing the target medium to the droplet ejector. The target medium is immovably held with respect to the droplet ejector.

Abstract: An example device includes a first droplet ejector including a first nozzle to eject droplets of a first fluid, and a first target medium positioned relative to the first droplet ejector to receive the droplets of the first fluid from the first droplet ejector. The example device further includes a second droplet ejector in fluid communication with the first target medium to receive a second fluid from the first target medium. The second droplet ejector includes a second nozzle to eject droplets of the second fluid.

Abstract: A rapid thermal cycling device can include a microfluidic reaction chamber, a dry reagent, and a heating element. The microfluidic reaction chamber can be defined between a substrate and a cover having an average space therebetween from 4 ?m to 150 ?m. The dry reagent can be positioned within the microfluidic reaction chamber. The heating element can be thermally coupled to the microfluidic reaction chamber to heat a fluid when introduced therein.

Abstract: A rapid thermal cycling device can include a static microfluidic reaction chamber that can be defined between a layered substrate and a cover that can have an average space therebetween from 4 ?m to 150 ?m. The layered substrate can include a heating element thermally coupled to the static microfluidic reaction chamber to heat a fluid when present therein. The layered substrate, the cover, or both can include a heat diffusing material thermally coupled to the static microfluidic reaction chamber to diffuse heat out from the fluid while remaining in the static microfluidic reaction chamber.

Abstract: An example device includes a first droplet ejector including a first nozzle to eject droplets of a first fluid, a second droplet ejector including a second nozzle to eject droplets of a second fluid, and a target medium. The example device further includes a mixing volume positioned between the first and second droplet ejectors and the target medium. The mixing volume is to receive the droplets of the first fluid and the droplets of the second fluid, provide mixing of the droplets of the first fluid and the droplets of the second fluid, and provide a mixture to the target medium.

Abstract: An object focuser may include a substrate, a sample fluid passage supported by the substrate, a first inertial pump supported by the substrate to pump a sample fluid entraining an object through the sample fluid passage, a first sheath fluid passage, a second inertial pump supported by the substrate to pump a first sheath fluid through the first sheath fluid passage, a second sheath fluid passage and a second inertial pump supported by the substrate to pump a second sheath fluid through the second sheath fluid passage. The first sheath fluid passage and the second sheath fluid passage are connected to the sample fluid passage at a convergence on opposite sides of the sample fluid passage.

Abstract: The present disclosure is drawn to microfluidic devices. In one example, a microfluidic device can include a microfluidic channel. A vent chamber can be in fluid communication with the microfluidic channel. A capillary break can be located between the microfluidic channel and the vent chamber. The capillary break can include a tapered portion and a narrowed opening with a smaller width than a width of the microfluidic channel. A vent port can vent gas from the vent chamber. The vent port can be located a distance away from the capillary break so that a fluid in the capillary break does not escape through the vent port.