Flow Control for Gels AND Biomaterials

The Elveflow OB1 is a pressure controller. It pressurises the gas above each precursor reservoir and holds that pressure to 0.005% of full scale, so the flow through your nozzle or chip follows the value you set. One to four channels run independently, which covers a flow-focusing junction, a coaxial nozzle or a several-component formulation. Paired with an Elveflow MFS or BFS flow sensor it holds a flow rate instead, with the sensor measuring and the controller adjusting the pressure to match. Nothing mechanical moves in your precursor, and the controller adds no dead volume to the line.

The Elveflow OB1 arrives configured with the channel count and pressure ranges you choose, driven from the Elveflow Smart Interface, with SDKs for Python, MATLAB, LabVIEW and C++ if you want to script it. Around it sits the fluidic line, and Elveflow supplies all of it. A pressure and vacuum source if you have no house air line, the reservoirs and their caps, the adapters and tubing. An MFS or BFS flow sensor to close the loop on flow, a MUX distribution valve to bring several precursors, a crosslinker or a wash down one line, and the chip at the far end. The OB1 drives the precursor and reports what it did; the chemistry and the curing are yours.

It drifts in pressure mode, and it holds in sensor mode, so the answer depends on which of the two you are running. In pressure mode you enter a pressure and the flow is whatever that pressure produces through your circuit, following Q = ΔP/R. As the precursor gels, R rises, and the flow falls even though the pressure is exactly where you left it. In sensor mode an Elveflow MFS or BFS sensor measures the flow and the Elveflow OB1 moves the pressure to match the value you asked for, holding a thickening precursor at a set flow rate through a long print. Pick pressure mode when the pressure is the physically meaningful quantity, and sensor mode when your geometry depends on the flow rate.

The Elveflow OB1 responds in about 10 ms, fast enough to make ink switching a structural tool. Published work alternating two ink channels with switching times down to 0.5 s produced fibre segments below 500 µm inside one continuous print. That 10 ms is the pressure at the controller; the flow at your nozzle settles afterwards, through the resistance and compliance of your tubing and chip, so short, stiff, narrow tubing gets you closer. A size change is the same operation, a new setpoint with no hardware to move. Where you need more materials than you have channels, or in a set order, an Elveflow MUX distribution valve switches between precursors on one line.

Count one channel per phase that has to flow at the same time as the others. A flow-focusing or coaxial geometry needs two, a core-shell with a carrier phase needs three, and a formulation whose proportions you set needs one per component. The Elveflow OB1 goes up to four independent channels in one instrument, each with its own setpoint and its own range, and it can be upgraded later if the geometry grows. Where the materials arrive in turn instead, one channel and an Elveflow MUX distribution valve carry several precursors down the same line. That screens a series of formulations on one chip at one setpoint, and keeps your channels for the phases that must run together. If you are unsure how your geometry maps onto channels, send us the design and we will go through it with you.

Yes, and it is one of the common ways the Elveflow OB1 is used in this field. You drive the aqueous precursor on one channel and the continuous phase on another. The ratio between those two setpoints, with your chip’s junction, sets the drop size, and the steadiness of both lines keeps the size distribution from spreading. Sweeping the ratio maps the dripping and jetting regimes in one session, with each point kept as a setpoint you can return to. An Elveflow MFS or BFS sensor closes the loop on either phase when a flow rate is the quantity you specify. Gelation stays your step: an ionic bath, a temperature change or a light source. For a turnkey spherical-bead setup Elveflow publishes a dedicated application pack, with the OB1 as the controller inside it. For core-shell drops, several compartments in one microgel or non-spherical particles, the same instrument drives the extra inlets.

The Elveflow OB1 comes in five ranges that together span −900 mbar to 8 bar, two of them combining vacuum with pressure. With an Elveflow MFS or BFS sensor closing the loop, the flow rates in reach run from 0.1 µL/min to 500 mL/min. The limit comes from the circuit: Q = ΔP/R, so the flow you get at a given pressure depends on tubing bore and length, nozzle diameter and the viscosity of your precursor. Choose the smallest range that covers your working pressures, because the stability and the minimum increment are both fractions of full scale.

It changes the resistance, not the way you work. A more viscous precursor means a higher R, so the same pressure gives a lower flow rate and you raise the setpoint to compensate. The Elveflow OB1 is offered up to 8 bar for that reason, and shorter, wider tubing is worth the trouble on a thick ink. If the viscosity climbs during the run, an Elveflow MFS or BFS sensor in the loop holds the flow rate as R rises. Where a precursor is too thick for the pressure available, our PSD syringe pump imposes the flow rate by displacement instead, and viscosity does not shift it in steady state. Send us the formulation and the viscosity you work at, and we will tell you which of the two routes holds up on your bench.

None of the instrument does. The Elveflow OB1 is a non-contact pump: it acts on the gas above the liquid, so your precursor stays inside its own path and the controller adds no dead volume. That path is your reservoir, the reservoir adapter, the tubing and your chip or nozzle. Elveflow tubing is PTFE, and each fluidic part lists its own wetted materials on its product page, so you can match your formulation and your solvents against them yourself. A flow sensor, when you use one, sits in that path too and lists its own wetted materials. Fewer parts in contact also means fewer places for a precursor to sit and start crosslinking.

Read it as a resistance problem, and the pressure tells you where it is. On the Elveflow OB1 in sensor mode, a rising pressure at a held flow rate says R is climbing, a partial blockage forming. In pressure mode the same event shows as a falling flow rate at a fixed pressure. To locate it, take the chip off and repeat: if the pressure needed drops back to its earlier value, the restriction is in the chip or nozzle, otherwise it is in the tubing, an adapter or a sensor channel. Crosslinked precursor at the nozzle, a partly cured plug from an earlier run and particles in a filler are the usual causes here. An Elveflow MPS pressure sensor with an MSR reader logs the pressure so you can see the rise starting instead of finding it afterwards, and a sequence can stop the run on a threshold.

Yes, and it is how most long runs are done. You build the pressure programme once in the Elveflow Smart Interface, give each stage its own duration, and the Elveflow OB1 works through it from the first drop to the last. Nobody has to sit at the panel, and the same file gives the same run next week, so a repeat batch compares with the first. Pressure and flow stream to CSV throughout, so you can see afterwards what the instrument actually did at every stage.

Yes, in both directions. The Elveflow OB1 has TTL lines in and out, at 0 or 5 V. It can start a sequence on a trigger from your motion controller, or fire a camera, a shutter or a UV source at a chosen step of its own sequence. The sequence is built once in the Elveflow Smart Interface and replayed, and pressure and flow stream to CSV while it runs, so each object comes with the settings that produced it. For tighter integration the SDKs drive the OB1 from Python, MATLAB, LabVIEW or C++, which is the usual route when the pressure has to follow a print path computed elsewhere.

That is the practical reason to drive a fabrication line by pressure. With the Elveflow OB1 the operating point is a number and a sequence you replay, held to 0.005% of full scale. The same file gives the same setpoints in another operator’s hands on another day, and the log shows what actually happened. The scatter left in your geometry then comes from the material and the chip. It also makes the method publishable: you report the value you set, with its range and its stability, and another lab has what it needs to reproduce your conditions.

It depends on the quantity you need to hold. The Elveflow OB1 pressure controller is the answer when the pressure is the meaningful quantity, and when you move between operating points during a run. It responds in about 10 ms, holds the pressure to 0.005% of full scale, and adds no moving part to the liquid. Ink switching, flow focusing, stop-flow cycles and fast size sweeps all sit here. Our PSD syringe pump takes the cases built the other way round, where you need a known delivered volume, or a flow rate that stays put as downstream resistance rises. The two coexist on the same bench. Tell us your precursor, your nozzle and what you need to keep constant, and we will settle it on your configuration.

Contact us through the form with your material system, the geometry you are making and the pressures or flow rates you work at. We will come back with an Elveflow OB1 configuration that fits, and answer setup questions before you buy.