QCM sensors · quartz crystals for the quartz crystal microbalanceThe surface is the experiment.

A quartz crystal microbalance reports what happens in the first few hundred nanometres above its electrode. openQCM sensors are 14 mm AT-cut quartz crystals at 5 and 10 MHz, with gold, platinum, stainless steel or silicon dioxide as the sensing surface.

The nine sensors Cleaning and care

Sensing face · ⌀ 12.0 mm electrode

Build a part number

AT5Cut · frequency 14Blank, mm 12Electrode, mm AUSurface WRAPContact

Surface

Frequency

Electrodes

Made for: Liquid biosensing
Mass sensitivity: 17.7 ng cm⁻² Hz⁻¹
Sensing film: ~10 nm Ti / ~200 nm Au
Quartz blank: ≈ 0.33 mm thick, 14 mm
Operating range: −20 to +125 °C
Box: 10 sensors · €289 excl. VAT

Buy in the store Data sheet, PDF Nine combinations exist. The ones that do not are switched off.

01 / Anatomy

Two electrodes, one side to contact.

Every sensor is an AT-cut quartz disc, 14 mm across, with a thin film electrode on each face. The front electrode is the sensing surface. It wraps around the edge of the blank, so both electrodes are contacted from the back and the sensing face stays free.

Cross-section, not to scale. The film takes the colour of the surface chosen above.

To scale

If the 0.33 mm of a 5 MHz quartz blank were as wide as this line, the 200 nm electrode film would be the hairline at its left end: about one part in 1600. That film is the whole experiment.

Thickness shear

The crystal shears.

An alternating voltage across the electrodes drives the quartz into a thickness shear resonance. Material that binds to the sensing surface moves with the crystal and lowers the resonance frequency.

How a quartz crystal microbalance works

Sauerbrey

Δm = −C · Δf / n

For a thin, rigid layer the frequency change is proportional to the added mass per unit area. C is 17.7 ng cm⁻² Hz⁻¹ at 5 MHz and 4.42 ng cm⁻² Hz⁻¹ at 10 MHz; n is the overtone number.

Run the Sauerbrey calculator

A thin listening layer

250 nm of water.

In liquid the shear wave decays within about 250 nm at 5 MHz and 180 nm at 10 MHz. Soft layers such as proteins, polymers or cells also dissipate energy, which is why frequency and dissipation are measured together.

QCM-D, frequency and dissipation

02 / Surfaces

Five surfaces, five chemistries.

The electrode is the surface your molecules meet. Choose the one your sample would meet outside the instrument: a noble metal, a working steel, or glass.

01 / Au
Gold

The general purpose surface: thiol monolayers, biosensing, protein and polymer adsorption, electrochemistry. Chemically noble.

~10 nm Ti / ~200 nm Au

AT5-14-12-AU-WRAP AT10-14-12-AU-WRAP AT10-14-6-AU-WRAP
02 / Pt
Platinum

Electrochemical QCM, catalysis and corrosive environments. A wide potential window, and a surface that can be regenerated many times.

~10 nm Ti / ~200 nm Pt

AT5-14-12-PT-WRAP AT10-14-12-PT-WRAP AT10-14-6-PT-WRAP
03 / SS316
Stainless steel 316

The steel of medical devices, implants and marine equipment: protein adsorption, biofouling, corrosion. More chloride resistant than 304.

~10 nm Ti / ~200 nm SS316

AT5-14-12-SS316-WRAP
04 / SS304
Stainless steel 304

The steel of food, dairy and process equipment: fouling and cleaning-in-place studies.

~10 nm Ti / ~200 nm SS304

AT5-14-12-SS304-WRAP
05 / SiO₂
Silicon dioxide

A hydrophilic, glass-like surface: supported lipid bilayers, vesicles, polyelectrolytes, surfactants.

~10 nm Ti / ~200 nm Au / ~50 nm SiO₂

AT5-14-12-SiO2-WRAP

03 / Frequency and electrodes

Thicker, or four times finer.

A 10 MHz crystal has four times the mass sensitivity of a 5 MHz crystal. A 5 MHz crystal is twice as thick and easier to handle.

5 MHz

17.7ng cm⁻² Hz⁻¹

blank ≈ 0.33 mm

10 MHz

4.42ng cm⁻² Hz⁻¹

blank ≈ 0.17 mm

5 MHz and 10 MHz at a glance
	5 MHz	10 MHz
Mass sensitivity (Sauerbrey, n = 1)	17.7 ng cm⁻² Hz⁻¹	4.42 ng cm⁻² Hz⁻¹
Nominal blank thickness	≈ 0.33 mm	≈ 0.17 mm
Decay length of the shear wave in water	about 250 nm	about 180 nm
Frequency shift in water near 25 °C	about +8 Hz/°C	about +23 Hz/°C
Overtones read by openQCM Q-1 and NEXT	up to n = 9	up to n = 5

12 / 5 mm

A large sensing electrode, for liquid cells.

A 12 mm front electrode and a 5 mm back electrode. The whole wetted area of the measurement chamber sits on the film.

6 / 6 mm, symmetric

Two equal electrodes, for gas and vacuum.

Symmetric 6 mm electrodes for gas phase, vacuum and thin film work, with an orientation flat on the blank so every sensor is mounted with the same orientation of the cut.

Every sensor

One blank, every instrument.

AT cut at 35° 15′, plano-plano, polished, 14 mm. The same blank fits openQCM NEXT, Q-1 and Wi2, and holders built for 14 mm Q-Sense type sensors.

04 / The range

Nine sensors, line by line.

The same rows for every sensor, so they can be compared. Values are those of the data sheets, version 1.0 of 11 November 2026; prices are read from the store once a day, VAT excluded.

Part number	Surface	Frequency	Electrodes	Made for	Sensitivity ng cm⁻² Hz⁻¹	Operating range	Box	Price	Documents and store
AT5-14-12-AU-WRAP	Gold	5 MHz	12 / 5 mm	Liquid biosensing	17.7	−20 to +125 °C	10 pcs	€289	PDF Store
AT10-14-12-AU-WRAP	Gold	10 MHz	12 / 5 mm	Liquid biosensing	4.42	−20 to +125 °C	10 pcs	€289	PDF Store
AT10-14-6-AU-WRAP	Gold	10 MHz	6 / 6 mm	Gas phase, vacuum and thin films	4.42	−20 to +125 °C	10 pcs	€249	PDF Store
AT5-14-12-PT-WRAP	Platinum	5 MHz	12 / 5 mm	Electrochemistry and liquid sensing	17.7	−20 to +70 °C	5 pcs	€259	PDF Store
AT10-14-12-PT-WRAP	Platinum	10 MHz	12 / 5 mm	Liquid biosensing and electrochemistry	4.42	−20 to +70 °C	5 pcs	€259	PDF Store
AT10-14-6-PT-WRAP	Platinum	10 MHz	6 / 6 mm	Electrochemistry, catalysis and gas phase	4.42	−20 to +70 °C	5 pcs	€249	PDF Store
AT5-14-12-SS316-WRAP	Stainless steel 316	5 MHz	12 / 5 mm	Biofouling and corrosion studies in liquid	17.7	−20 to +125 °C	5 pcs	€259	PDF Store
AT5-14-12-SS304-WRAP	Stainless steel 304	5 MHz	12 / 5 mm	Fouling and cleaning studies in liquid	17.7	−20 to +70 °C	5 pcs	€239	PDF Store
AT5-14-12-SiO2-WRAP	Silicon dioxide	5 MHz	12 / 5 mm	Lipid bilayers, polymers and silica surface studies	17.7	−20 to +125 °C	10 pcs	€459	PDF Store

All sensors: AT-cut quartz, 14 mm, fundamental mode, wrapped electrodes with single side contact, titanium adhesion layer, frequency tolerance ± 5 kHz (± 7 kHz for SS304). Resonance resistance, shunt capacitance and the values still being measured are in each data sheet.

05 / Cleaning and care

Clean it like the film it is.

The sensing film is about 200 nm thick, on 10 nm of titanium. A treatment that restores gold can strip a stainless steel film or dissolve a silica layer, so every surface has its own procedure. Each step in the data sheets cites the work it comes from.

Six rules for every sensor

Hold it by the edge. Plastic tipped tweezers and powder free nitrile gloves. Never touch or wipe the electrodes or the wrapped contact.
Dry from the centre outwards with filtered, oil free nitrogen. A droplet left to evaporate leaves a ring of residue.
Finger tight only. Clamping force shifts the resonance: three point clamping moved 10 MHz crystals by up to 3 ppm.
Wait for the baseline. Swelling O-rings and contact pressure cause slow drift in the first minutes after mounting.
No ultrasonic bath. Cavitation is itself used as a delamination test for sub-micrometre coatings.
One pretreatment per series. Different cleaning methods give different surface states, and different sensor responses.

What each surface can take.

SafeCautionAvoidNeverNot rated

Treatment	Gold	Platinum	Stainless steel	Silicon dioxide
Water, ethanol, isopropanol, acetone	No measurable etching of gold, titanium, chromium or quartz.	No measurable etching of platinum, titanium or chromium.	Compatible. Use ultrapure water, free of chloride.	No etching of silica, titanium, chromium or gold.
UV/ozone	Up to 30 min. It leaves a thin gold oxide: 20 min in absolute ethanol reduces it.	At no more than 80 °C.	Short, 5 to 10 min, followed by a water rinse. A long exposure changes the oxide and the wetting.	Removes organics and does not etch the oxide.
Oxygen plasma	Low power and short: 22 W for 85 s caused no damage on openQCM sensors.	Forms platinum oxide or roughens the surface.	Forms Cr(VI) and changes oxide and wetting. Argon plasma is the safe choice on steel.	Removes organics and does not etch the oxide.
Chloride media: PBS, saline, cell media	Only under anodic potential: chloride then corrodes thin gold.	Under anodic polarization, traces of chloride increase platinum dissolution.	For the duration of the experiment only, then rinse. Never store the sensor in it.	Neutral buffers are the standard media for bilayers on silica.
Dilute NaOH or KOH	50 mM KOH for cyclic voltammetry, within the potential limits of the data sheet.	Short contact only: alkali dissolves quartz faster at higher pH and temperature.	0.1 to 0.25 M NaOH, up to 50 °C, up to 15 min: it removes proteins.	–
Hydrogen peroxide and its mixtures	Hot H₂O₂ etches chromium at 110 nm/min: avoid it on chromium adhesion layers.	Especially warm: it etches chromium at 110 nm/min at 50 °C.	–	NH₄OH/H₂O₂ mixtures undercut titanium and chromium at the edges.
Hot or concentrated NaOH and KOH	Etches the quartz and softens the titanium.	–	Above 0.25 M or above 50 °C it etches the quartz and softens the titanium.	30 % KOH at 80 °C removes 50 nm of deposited silica in a few minutes.
Hydrochloric acid	–	Hot, with oxidants (Cl₂, H₂O₂, HNO₃), it dissolves platinum.	Also HCl-based descalers and FeCl₃, the solution used to induce pitting in corrosion tests.	Dilute and short only: it does not etch silica, but the adhesion metal is exposed at the edges.
Acid piranha	Titanium at 240 nm/min. It caused the largest loss of performance on openQCM sensors.	Titanium at 240 nm/min: it undercuts the adhesion layer.	Etches nickel quickly and undercuts the titanium.	It does not etch silica or gold, but undercuts the electrode at edges and pinholes.
Aqua regia, also diluted	Dissolves gold at 680 nm/min.	Etches platinum at 3.6 nm/min at 30 °C, faster when hot.	–	Dissolves the gold underneath through pinholes and edges.
HF and fluorides	Titanium at 1100 nm/min, and it etches the quartz.	Titanium at 1100 nm/min in 10:1 HF, and it etches the quartz.	Attacks titanium and quartz.	10:1 HF removes the 50 nm of silica in about 2 min.
Ultrasonic bath	Cavitation is itself used as a delamination test for sub-micrometre coatings.	Cavitation is itself used as a delamination test for sub-micrometre coatings.	Degrease by immersion instead of ultrasound.	Cavitation damages polished surfaces.
Abrasives, polishing, wiping	They remove the 200 nm film.	They remove the 200 nm film.	They remove the 200 nm film.	They remove the film.

Select a rating to read the reason. Safe: no measurable effect in the conditions given. Caution: usable within the stated limits. Avoid: damages part of the sensor. Never: destroys the film, the adhesion layer or the quartz. Etch rates from Williams, Gupta and Wasilik (2003).

Three levels, gentlest first.

Gold

Gold is noble, but a clean gold surface takes up hydrocarbons from the air within minutes and binds sulfur compounds and proteins strongly.

Level 1 · between measurements
Flush with buffer, then ultrapure water. Rinse the gold face with ethanol or isopropanol, then water. For protein residues, 10 to 15 min in alkaline SDS (pH 11) at room temperature. Dry with nitrogen.
Level 2 · before use
Solvent rinse, then a low power oxygen plasma (about 20 W, 60 to 90 s) or UV/ozone for 15 to 30 min, then 20 min in absolute ethanol to reduce the gold oxide. With a potentiostat: 10 cathodic sweeps in 50 mM KOH.
Level 3 · deep cleaning
Thiol monolayers: reductive desorption in 0.5 M KOH, or 0.5 M NaBH₄ for 10 min. Proteins: alkaline SDS, then plasma or the electrochemical sequence. Acid piranha is the last resort: expect to lose the sensor.

The full procedure, with its references, in the data sheet

Platinum

Platinum withstands strong oxidation, but it dissolves slowly under potential cycling above 1.15 V, and a dissolved monolayer shows as a frequency drift.

Level 1 · between measurements
Rinse with the measurement solvent or buffer, then ultrapure water; ethanol or isopropanol after organic or gas phase work. Dry with nitrogen or argon. With a potentiostat: 10 to 20 cycles between 0.05 and 1.20 V in deaerated 0.5 M H₂SO₄.
Level 2 · before use
Acetone for 10 to 30 min, then isopropanol and water. Optionally UV/ozone for 10 to 20 min at no more than 80 °C. Electrochemical activation in 0.5 M H₂SO₄ or 0.1 M HClO₄ until consecutive voltammograms overlap.
Level 3 · deep cleaning
Solvent soak for up to 1 h, UV/ozone two or three times with a water rinse in between, then potential cycling. Carbon monoxide, sulfur and metal adatoms each have their own anodic treatment. Never flame anneal.

The full procedure, with its references, in the data sheet

Stainless steel

A sputtered steel film forms a uniform passive layer. PBS carries about 4900 mg/L of chloride: rinse it out after every run and never store the sensor in it.

Level 1 · between measurements
Flush with the running buffer, then ultrapure water for 5 min. Protein or soft soil: 0.1 M NaOH at 20 to 40 °C for 10 min, then water. Optionally a rinse in 0.5 to 1 % HNO₃ or 1 to 2 % citric acid.
Level 2 · before use
Acetone, then isopropanol, 5 to 7 min each, by immersion. 0.1 M NaOH or a chloride-free alkaline detergent for 10 to 15 min. Then argon plasma for a few minutes at low power, or UV/ozone for 5 to 10 min. Rinse with water before mounting.
Level 3 · deep cleaning
Proteins and biofilms: enzymatic detergent at 40 to 50 °C, then 0.25 M NaOH. Mineral scale: 1 % HNO₃ or 2 to 5 % citric acid. Citric acid re-passivation only after exposure to chloride. Never hydrochloric acid.

The full procedure, with its references, in the data sheet

Silicon dioxide

The silica layer is about 50 nm thick and deposited, not grown: fluoride and hot alkali consume it quickly. Losing 1 nm shows as about +12 Hz.

Level 1 · between measurements
Flush the buffer out with ultrapure water. To remove a lipid layer: 2 % Hellmanex III at 20 to 25 °C for 10 min, or ethanol or isopropanol for 5 to 10 min. Flush with water for at least 10 min, rinse and dry with nitrogen.
Level 2 · before use
Solvent rinse, then 2 % Hellmanex III at 20 to 35 °C for 10 to 30 min, without ultrasound. Rinse both faces. Activate with oxygen or air plasma for 1 to 2 min, or UV/ozone for 10 to 20 min. Use within 30 to 60 min.
Level 3 · deep cleaning
Lipids: Hellmanex at 30 to 35 °C for 30 min, then a longer plasma or UV/ozone. Proteins: enzymatic detergent for 30 to 60 min. Polymers: a good solvent, then oxygen plasma. Piranha is not recommended.

The full procedure, with its references, in the data sheet

Measured on openQCM sensors

Every cleaning costs a little.

On openQCM 10 MHz gold sensors, three regeneration cycles reduced the sensor performance by 7 % with electrochemical cleaning, 16 % with oxygen plasma and 25 % with piranha (Wasilewski et al., 2022). Always start with the lowest level that restores the baseline.

Electrochemical7 %
Oxygen plasma16 %
Piranha25 %

Replace the sensor when

the quartz edge is cracked or chipped, or the electrode is scratched;
the electrode peels, seen from the contact side, or stays discoloured;
the baseline is noisy or the motional resistance has risen;
the frequency in air drifts from one cleaning to the next;
the cleanliness test of its data sheet no longer passes.

Record the frequency in air of every new sensor and after each deep cleaning: comparing the values is the simplest way to follow the electrode.

06 / Documents

The data sheets.

Specification, drawings, three levels of cleaning, a chemical compatibility table and the literature behind every step, for each sensor. The catalogue of the whole range asks only who is reading.

Catalogue · PDF · 6.6 MB openQCM quartz sensors: specifications, cleaning and care Download the catalogue

Sources of the figures on this page

G. Sauerbrey, Verwendung von Schwingquarzen zur Wägung dünner Schichten und zur Mikrowägung, Zeitschrift für Physik 155, 206–222 (1959). doi:10.1007/BF01337937
K. K. Kanazawa, J. G. Gordon, The oscillation frequency of a quartz resonator in contact with liquid, Analytica Chimica Acta 175, 99–105 (1985). doi:10.1016/S0003-2670(00)82721-X
D. Johannsmann, The Quartz Crystal Microbalance in Soft Matter Research, Springer (2015). doi:10.1007/978-3-319-07836-6
K. R. Williams, K. Gupta, M. Wasilik, Etch rates for micromachining processing, Part II, Journal of Microelectromechanical Systems 12, 761–778 (2003). doi:10.1109/JMEMS.2003.820936
T. Wasilewski et al., Development and Assessment of Regeneration Methods for Peptide-Based QCM Biosensors in VOCs Analysis Applications, Biosensors 12, 309 (2022). doi:10.3390/bios12050309
D. Scaccabarozzi et al., Measurement of the Instrumental Effect Caused by Flexure Clamping on Quartz Crystal Microbalances, Applied Sciences 15, 9261 (2025). doi:10.3390/app15179261

The complete reference list is in the catalogue.

07 / Talk with us

Not sure which surface? Ask us.

Tell us the sample, the liquid and what you want to see. We will tell you which sensor fits, and how to clean it between runs.

Discuss your experiment All sensors in the store Sensor questions in the FAQ

QCM sensors · quartz crystals for the quartz crystal microbalanceThe surface is the experiment.

Build a part number

The crystal shears.

Δm = −C · Δf / n

250 nm of water.

Gold

Platinum

Stainless steel 316

Stainless steel 304

Silicon dioxide

A large sensing electrode, for liquid cells.

Two equal electrodes, for gas and vacuum.

One blank, every instrument.

Six rules for every sensor

What each surface can take.

Three levels, gentlest first.

Gold

Platinum

Stainless steel

Silicon dioxide

Every cleaning costs a little.

Replace the sensor when

Sources of the figures on this page

Not sure which surface? Ask us.