Most people arrive here the same way: a line reading "EMG 705, Ferrotec" in someone's methods section, then a search for a supplier who will sell in small quantities rather than by the drum. This page indexes what those papers actually did with the fluid — grade, dilution ratio, anti-aggregation recipe, and the numbers the authors published — so you can reproduce a setup instead of guessing. Standard packs from 10 mL, batch number and COA in the box.
Four directions, four different ways of using the same fluid. Find your row first, then read the paper detail below.
Fill a capillary, hollow-core fiber or FPI cavity and modulate through the field-dependent refractive index. The literature default is EMG 705: 10 nm particles, 22 mT, viscosity under 5 cP — thin enough to fill by capillary action without a pump.
Two ways to use it: as the dispersed phase to generate magnetic droplets (T-junction, flow focusing), or as the continuous phase that magnetizes non-magnetic droplets. The critical step is 0.1% Tween 20 to stop coalescence, and diluting the stock before it reaches 50 µm channels.
Diluted 1:3 with deionized water, EMG 705 works as a liquid mold on uncured PDMS. A magnet below pulls the droplet into a spherical cap; cure it and you have a concave lens. That is the APL 2019 paper, and the tooling cost is close to zero.
EMG 705 is stabilized by an anionic surfactant at pH 8-9, so particles are negatively charged and suit electrostatic assembly; covalent work goes through EDC/NHS or silica coating plus APTES. Adding salt or shifting pH will break the colloid.
Grouped by direction. Each entry gives the grade, the critical step and the numbers worth reusing. Titles link to the original.
| Direction | Paper | Grade | How it was used / reusable data |
|---|---|---|---|
| Fiber-optic field sensing EFPI cavity |
Magnetic Sensing with Ferrofluid and Fiber Optic Connectors Homa & Pickrell · Sensors 2014, 14(3):3891–3896 · doi:10.3390/s140303891 |
Two water-based types (EMG family) | Ferrofluid fills the air gap between two fiber-optic connectors to form an extrinsic Fabry–Pérot cavity. Detection over 0.5–12 mT, sensitivity 0.3–2.3 nm/mT, estimated resolution 0.04 mT. Finding: sensitivity depends strongly on which ferrofluid is used — changing grade means recalibrating from scratch. |
| Fiber-optic field sensing Multimode interference, intensity modulated |
A Highly Sensitive Intensity-Modulated Optical Fiber Magnetic Field Sensor Based on the Magnetic Fluid and Multimode Interference Journal of Nanomaterials 2017, Article ID 9573061 |
EMG 705 | A no-core fiber spliced between two single-mode fibers (SNS structure), immersed in EMG 705 and sealed in a capillary, ends secured with UV adhesive. Field swept 0–240 Oe in 15 Oe steps with 5 min settling per point. Data used: density 1.19 g/cm³, Ms 220 Oe; intensity demodulation rather than wavelength shift keeps the readout electronics simple. |
| Fiber sensing Taper modal interferometer, temperature cross-compensation |
Potential for Simultaneous Measurement of Magnetic Field and Temperature Utilizing Fiber Taper Modal Interferometer and Magnetic Fluid IEEE Photonics Journal 2017 |
EMG 705 diluted to ~10% in water |
A tapered fiber (waist around 10 µm) sealed in a capillary filled with diluted ferrofluid; wavelength and extinction ratio are read together to demodulate field and temperature simultaneously. Key point: the authors diluted EMG 705 to roughly 10% — at full concentration the loss swamps the interference fringes. |
| Review Selection overview |
Optical Fiber Magnetic Field Sensors Based on Magnetic Fluid: A Review Sensors 2018, 18(12):4305 |
— | Sorts magnetic-fluid fiber sensors into three families: grating-based (FBG/TFBG/LPG), interferometric (FPI/MZI/Michelson/Sagnac) and other (SPR, etched, tapered, U-shaped). Read this before you start; it saves about two weeks of literature search. It also names the two intrinsic limitations: magnetic hysteresis response time and the temperature dependence of refractive index. |
| Microfluidics Magnetic droplet generation and manipulation |
Generation and Manipulation of Magnetic Droplets Al-Hetlani, Iles & Pamme · MNF 2009 (Brunel institutional repository) |
EMG 507 + EMG 705 |
Magnetic droplets generated on a glass chip by T-junction and flow focusing, with perfluorodecalin plus 10:1 perfluorooctanol as the oil phase. Two pitfalls: hydrophilic glass must first be treated with a fluorosilane (trichloro(1H,1H,2H,2H-perfluorooctyl)silane in isooctane) for 15 min; droplet deflection and splitting are done with a permanent magnet — no electromagnet needed. |
| Microfluidics Non-spherical polymer particles |
Magnetic-Field-Assisted Fabrication and Manipulation of Nonspherical Polymer Particles in Ferrofluid-Based Droplet Microfluidics Langmuir 2015 |
EMG 705 | Inverted use: EMG 705 is the continuous phase and the polymer monomer is the dispersed phase; the field flattens droplets into ellipsoids and strings them into chains, then UV cures them. EMG 705 with 0.1% Tween 20 to prevent coalescence; PDMS channels 44 µm deep; 0.36 T at the magnet surface. Reported: particle volume fraction 5.8%, particle size 10.2 nm, initial susceptibility 1.17, Ms 325 G. |
| Microfluidics Wetting transition on superhydrophobic surfaces |
Resonance induced wetting state transition of a ferrofluid droplet on superhydrophobic surfaces Experimental Thermal and Fluid Science 2014 |
EMG 705 | A 1–10 µL ferrofluid droplet sits on a microstructured superhydrophobic surface and is driven by a flat electromagnet; at the resonance frequency (around 44 Hz) the droplet undergoes a Cassie-to-Wenzel transition. Note: at these volumes the magnetic body force is weak — the low adhesion of the superhydrophobic surface is what makes the transition possible. |
| Biosensing Graphene Hall sensor, whole blood |
Highly stable integration of graphene Hall sensors on a microfluidic platform for magnetic sensing in whole blood Microsystems & Nanoengineering (Nature) 2023 |
EMG 705 3.9% v/v |
50 µm ferrofluid droplets generated by flow focusing (water-in-oil), oil phase HFE 7500 with 2% Krytox, PDMS channels 50×50 µm to guarantee plug flow, read out with a graphene Hall sensor. Key figure: droplet magnetic moment 1.71×10⁻¹⁰ A·m², the same order as immunomagnetically labelled cells — this is the standard way to build a control for cell detection. |
| Optical components PDMS concave lens |
Fabrication of polymeric lenses using magnetic liquid molds Applied Physics Letters 114, 203701 (2019) |
EMG 705 1:3 with DI water |
Ferrofluid diluted 1:3 with deionized water is dropped onto uncured PDMS; a magnet underneath pulls the droplet into a spherical cap; cure at 75 °C for 40 min; demold for a plano-concave lens, with the ferrofluid recoverable. Reported: interfacial tension 50 mN/m, density 1190 kg/m³, initial susceptibility 4.04. Water-based ferrofluid does not adhere to cured PDMS, which is what allows clean demolding. |
Copyright in these papers remains with the authors and publishers. This page provides summaries, grade annotations and links only; no full text is reproduced. If you are an author and would like wording adjusted, contact us and we will change it.
Figures from the Ferrotec water-based EMG parameter table. Carrier is deionized water in every case; appearance is a dark brown low-viscosity liquid.
| Grade | Saturation magnetization (Gs) | Ms (mT) | Viscosity (cP) | Typical use |
|---|---|---|---|---|
| EMG 601P | 440 | 44 | <5 | Strongest magnetic response in a water-based grade |
| EMG 700 | 355 | 35.5 | <10 | Magnetic domain observation, higher-Ms sensing |
| EMG 603P | 330 | 33 | <5 | High-strength water-based work |
| EMG 304 | 275 | 27.5 | <10 | Biomedical, magnetic separation |
| EMG 705 / 605 / 605P | 220 | 22 | <5 | Most cited, first choice for fiber sensing and microfluidics |
| EMG 507 / 607 / 607P | 110 | 11 | <5 | Moderate response, where low concentration is required |
| EMG 308 / 408 / 508 / 608P / 708 | 66 | 6.6 | <5–10 | Weak response, low-concentration controls |
| EMG 509 | 33 | 3.3 | <5 | Very low concentration control experiments |
EMG 705 datasheet figures: particle size 10 nm · Ms 220 Gs / 22 mT · viscosity <5 cP · density 1.19 g/cm³ at 25 °C · initial susceptibility 0.32 (CGS) / 4.04 (SI) · particle volume concentration 3.9% · pH 8–9 · anionic surfactant · black to dark brown liquid.
This is where people most often buy the wrong product. Ferrofluid and functionalized magnetic beads are different classes and do not substitute for each other.
EMG 705 is stabilized by an anionic surfactant at pH 8–9, so particles carry a negative surface charge. Positively charged proteins, peptides and aminated surfaces will adsorb electrostatically. This is physisorption, not a covalent bond — change the wash conditions and it comes off. Fine for short experiments, not for anything that needs long-term stability.
Either EDC/NHS activation of carboxyl groups to form an amide bond with an amine-bearing ligand, or silica coating with TEOS followed by APTES amination to put amines on the surface. Both must be trialled in buffer first, because shifting pH and adding salt destabilizes the colloid.
Off-the-shelf carboxyl- or amine-functionalized ferrofluids are rare. If what you actually need is a particle with functional groups already attached, 100 nm to 1 µm, usable for capture and separation, that is a functionalized magnetic bead — a different product category with different suppliers. We will not sell you ferrofluid dressed up as beads.
Water-based ferrofluid relies on electrostatic repulsion to stay dispersed. Adding NaCl, switching to PBS, or moving pH away from 8–9 compresses the double layer and causes aggregation. For physiological conditions, first run a dilution tolerance series: 1:10, 1:50, 1:100, and see which dilution still holds for 24 h in your buffer.
Both are water-based with the same nominal Ms of 220 Gs (22 mT) and viscosity under 5 cP; the difference is in particle concentration and surfactant formulation. EMG 705 dominates the published literature and is the experimental default. If your system is sensitive to ionic strength or pH, take 10 mL of each and compare — a datasheet will not reveal the difference.
Ferrotec states that water-based particles agglomerate readily and recommends use within three months of purchase. Past that you see viscosity rising, magnetic response slowing and sediment forming. Store dark at 4–25 °C, never freeze, and split into small vials after opening.
EMG 705 is the mainstream choice: 10 nm, 22 mT, under 5 cP, field-tunable refractive index, and thin enough to fill an FPI cavity or capillary by capillary action. For stronger response, EMG 700 (35.5 mT) or 601P (44 mT) work but are harder to fill. When compensating temperature, remember the fluid's own refractive index is temperature dependent.
Three approaches with literature backing: 0.1% Tween 20 in the continuous phase; HFE 7500 with 2% Krytox as the oil phase; fluorosilane treatment of glass chips. And dilute the stock before it meets 50 µm channels — neat fluid will block them.
EMG 705 is anionic-surfactant stabilized with a negative surface charge, suitable for electrostatic assembly; covalent work requires your own EDC/NHS or silica-plus-APTES step. If you need beads with groups already attached (100 nm and up), that is a functionalized bead product, not a ferrofluid, and the two are not interchangeable.
The minimum sales unit is 10 mL, decanted from original Ferrotec stock with batch number and COA. Typical literature volumes: 10–50 µL per FPI or capillary filling; 0.05–1 mL/h as a microfluidic continuous phase; 1–10 µL per droplet experiment. 10 mL generally covers more than 100 small trials — enough to finish parameter scouting before buying 100 mL.
Yes. Each shipment carries the batch number plus measured Ms, density and pH, with the Ferrotec original English SDS. If you need grade and batch details written for a materials-and-methods section, say so on the order and we include a citable material statement.
EMG 705 / 605 / 507 / 707 normally in stock. Standard packs from 10 mL ship the same day. Batch number and COA in every box, and the grade information you need to cite, on request.
In your message, tell us three things: the direction (fiber sensing / microfluidics / conjugation), the Ms level you need, and whether you have already diluted the stock. With those, we can name a grade in one reply.