Liquid dosing systems

In order to dose drops precisely and reproducibly different tubeless direct dosing systems are available. They utilise glass or disposable syringes which provides for short preparation times and minimal cleaning efforts. This applies to both manually positioned single syringe modules and to multi-dosing systems with up to four electronically selectable and positioned syringes. Especially small droplets that are required to analyse micro-structured samples can be created with special nanolitre or picolitre dosing systems.

Direct dosing systems

The direct dosing systems are attachments that are mounted directly on the illumination housing of all OCA systems. The direct dosing systems allow either for a manual positioning of one or two electronic syringe modules or an automatic electronical positioning of between one and four electronic syringe modules.

Manual direct dosing systems

The single direct dosing system SD-DM can be used to manually position one electronic syringe module. It is the ideal entry level solution for measuring surface and interfacial tension with the pendent drop method. The SD-DM consists of one syringe module carrier with fine adjustment screws for the axial and horizontal needle positioning and a connection cable

The double direct dosing system DD-DM can dose two different liquids on a substrate for the determination of the surface energy. The DD-DM consists of two syringe module carriers with fine adjustment screws for the axial and horizontal needle positioning and two connection cables

Electronic multiple direct dosing systems DDE/x

The electronic multiple direct dosing system DDE/x offers a precise electronic syringe selection and positioning. The DDE/x can be controlled with the TP 50 control panel and via the OCA software. Due to the ability to electronically select and position up to four different liquids above a sample the determination of the surface energy of solids can be easily automated.

The DDE/x features the following technical data:

• vertical travel distance of a syringe module: 20 mm; resolution ±0.04 μm
• horizontal travel distance of a syringe module: ±4.9 mm; resolution ±0.2 μm

Depending on the version up to four electronic syringe modules can be used:

• DDE/1 with one syringe module carrier
• DDE/2 with two syringe module carriers
• DDE/3 with three syringe module carriers
• DDE/4 with four syringe module carriers

Electronic syringe module ESr-N

The electronic syringe modules ESr-N which are usable with all dosing systems work with glass or disposable syringes and dose down to typically 1 μl small drops. Due to the electronic piston drive, the ESr-N can automatically dose precise liquid volumes. Moreover, the ESr-N is already prepared for nanolitre dosing.

The ESr-N features the following technical data:

• piston travel speed: 0.2 μm/s … 10 mm/s; ±0.1 μm/s

The achievable dosing rates depend on the utilised syringe. Some typical dosing rates are:

• 0.01 … 5.28 μl/s with DS 100/GT
• 0.01 … 26.39 μl/s with DS 500/GT
• 0.02 … 52.82 μl/s with DS 1000/GT
• 0.02 … 55.30 μl/s with DS-D 1000 SF

Dosing systems for microstructures

An essential requirement for an accurate contact angle measurement is that the drop does not touch or wet beyond the edge of the test surface. This poses the challenge to dose especially small drops when analysing micro-structured samples like printed circuit boards, small medical products, lithographic structures, precision mechanics and assembly components, wires and single fibres. That challenge is met by innovative special dosing systems from DataPhysics Instruments.

The microlitre-sized drops dosed with a standard dosing system have base diameters in the millimetre range, depending on the contact angle. This equals about the size of a pin head.

With a nanolitre dosing system from DataPhysics Instruments droplets down to volumes a hundred times smaller, typically 10 nanolitres, can be dosed. These drops fit, for example, into the screw threads of a dental implant whose surface is to be investigated.

The mesh structure of a coronary stent presents an even smaller test area. Its surface properties have to be optimised in order to prevent the vessel from being blocked by tissue regeneration. In this case the picolitre dosing system PDDS is utilised to create drops down to 30 picolitres.

Dosing systems brochurefile_download

Nanolitre dosing system

The standard electronic syringe module ESr-N can easily be upgraded to a nanolitre dosing system by the addition of a nanolitre dosing valve. Thus contact angle measurements on micro-structured samples become possible with little effort.

With an air-filled syringe in the ESr-N module, the liquid in the dosing tube is pushed against a magnetic dosing valve. The valve is triggered by the OCA software. This setup allows to reproducibly dose up to 250 droplets per second down to 10 nl.

Picolitre dosing system PDDS

Dosing picolitre droplets on solid substrates carries optical contact angle measurement to the extremes. DataPhysics Instruments’ newly developed picolitre dosing system PDDS enables to reproducibly dose droplets of down to 30 picolitres. Hence, depending on the contact angle, drop base diameters considerably below 100 micrometres are achieved. Even with this high precision the picolitre dosing system PDDS is capable of dosing up to 1000 droplets per second.

What makes working with the PDDS particularly easy are the disposable cartridges used as test liquid containers. Their volume is only 100 microlitres being economic regarding both material cost and waste. Moreover, time-consuming cleaning procedures are not necessary and cross-contamination is impossible. This makes working with even the most challenging formulated liquids, including inks or surfactant solutions, routine.

Pressure-based double dosing system DDS-P

With the pressure-based double dosing system DDS-P two liquid drops can be dosed onto a solid sample simultaneously. Together with an optical contact angle measuring and contour analysis system of the OCA series the determination of the surface energy of solids is exceptionally fast and easy

The DDS-P is primarily designed for the test liquids water and diiodomethane, but other liquids can be used as well. The liquid reservoirs hold enough liquid for up to 3000 individual measurements.

The OCA software uses the DDS-P to dose two drops, automatically measures their contact angles and determines the surface energy—all with just one click. The entire process from starting the measurement to receiving the result takes less than a second.

In our application note you will learn how the pressure-based double dosing system DDS-P can be used to perform a one-click surface energy determination.

Advantages & main applications of the DDS-P

• fast analysis of the surface energy of solids
• objective and user-independent results
• quality assurance of coatings, surface treatments and other production processes
• surface characterisation in research and development departments with high sample throughput rates
• evaluation of surface cleaning processes

To the application notenavigate_next DDS-P brochurefile_download

Dosing syringes and needles

The OCA product series comprises a wide range of different dosing syringes and suitable needles. Inside the electronic syringe module ESr-N gas tight glass syringes can be used as well as cost efficient disposable syringes. In the following is a selection of the most important syringes:

• DS 100/GT gas tight 100 μl glass syringe
• DS 500/GT gas tight 500 μl glass syringe
• DS 1000/GT gas tight 1000 μl glass syringe
• DS-D 1000 SF silicon oil free and solvent resistant 1000 µl disposable syringe
• DS-D 3000 LL 3000 µl disposable syringe with Luer-Lock connector

With different needle types and sizes intended for either sessile or pendant drop or captive bubble measurements the right tool for every task is always at hand. For use with glass syringes needles made of stainless steel and made of stainless steel with PTFE coating are available. For use with the disposable syringes disposable needles are also available. The needles are arranged in groups according to the standard application of the needle:

• SNS xx dosing needles for sessile drop measurements
• SNP xx dosing needles for pendant drop measurements
• SNC xx upwards bent dosing needles for captive bubble measurements
• SNS-D xx disposable dosing needles for sessile drop measurements
• SNP-D xx disposable dosing needles for pendant drop measurements

Hydrophobisation kit for dosing needles

For a proper pendant drop evaluation and an easy placement of drops for the sessile drop method a wetting of the outer needle surface should be avoided. The hydrophobisation kit contains a specially formulated coating liquid that can be used to treat dosing needles before use. After treatment the needle surface is highly hydrophobic and unwanted wetting is far less likely.

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Syringe heating device SHD

With the syringe heating device SHD a syringe inside the electronic syringe module ESr-N can be heated using a liquid circulator bath. Hence, depending on the used circulator syringes and the contained liquids can be temperature controlled from -10 … 90 °C.

The SHD consists of the following parts:

• heating jacket for easy mounting and demounting of syringes
• Pt100 temperature sensor

Environmental chambers

With different environmental chambers measuring temperatures from -30 °C to 700 °C can be reached. All temperature chambers feature three windows made of special optical glass for observation and measurements with the OCA models as well as a set of two Pt 100 temperature sensors and an inert gas inlet. Also included with every temperature chamber are special cover plates in order to optimization the needle entry gap for varying samples.

TFC 100Pro

The liquid temperature control unit TFC 100Pro is used in conjunction with a liquid circulator bath. The TFC 100Pro features:

• temperatures of -10 … 100 °C
• temperature reading module TRM 100 for temperature measurements with OCA devices
• prepared for connection to humidity generator HGC 20/30
• optional triple diffusor TDI 100 to prevent condensation at the windows while working below room temperature by using a dry gas flow

TPC 160U

The Peltier temperature control unit TPC 160U utilises an electric Peltier system for temperature control. The TPC 160U requires a liquid counter cooling and features:

• temperatures of -30 … 160 °C
• TC-U PID controller for temperature setting
• prepared for connection to humidity generator HGC 20/30
• optional triple diffusor TDI 160 to prevent condensation at the windows while working below room temperature by using a dry gas flow

TEC 400U and TEC 700U

The electrical temperature control units TEC 400U and TEC 700U use electrical resistance heating of the chamber floor and lid. The TEC 400U and TEC 700U feature:

• temperatures from room temperature to 400 °C or 700 °C, respectively
• one / two TC-U PID controller for temperature setting
• connector for optional counter cooling with pressurised gas

Electrical needle heating devices NHD

Dedicated to investigating the properties of metals, polymers or hot melts in their liquid state are the electrical needle heating devices NHD 400U and NHD 700U. This special piece of development enables the dosing of molten solids at temperatures up to 400 °C or 700 °C, respectively. Hence the surface tension of, for example, molten aluminium can be determined.

The NHD 400U and NHD 700U feature:

• temperatures from room temperature to 400 °C or 700 °C, respectively
• cannula heater with integrated temperature sensor
• ceramic cannula with plunger
• option for glass syringes with NHD 400U available
• heating carrier with fine adjustment screws for the axial and horizontal cannula positioning
• TC-U PID controller for temperature setting

High temperature furnace HTV 1800

Inside the high temperature furnace HTV 1800 from DataPhysics Instruments contact angle measurements at up to 1800 °C and under vacuum down to 10^-5 mbar, or inert gas atmosphere, are possible.

The high temperature furnace HTV 1800 is available as part of an OCA 25 special model.

OCA 25-HTV 1800 brochurefile_download

High pressure measuring system PMC 750

Inside the high pressure chamber PMC 750 from DataPhysics Instruments interfacial tensions and contact angles can be measured at pressures of up to 750 bar and under temperature conditions ranging from -30 °C to 200 °C.

The high pressure chamber PMC 750 is available as part of an OCA 25 special model.

OCA 25-PMC 750 brochurefile_download

Humidity generators of the HGC series

The humidity generators of the HGC series allow for a reliable control of the relative humidity, in the range of 5 % to 90 %, inside environmental chambers from DataPhysics Instruments or other suppliers. Due to the integrated touch screen the system can be operated without additional software and is directly ready for use. Of course, the software of the DataPhysics Instruments measuring instruments includes, integrated, HGC humidity control.

Contact us nowmail_outline To the HGC seriesnavigate_next HGC brochurefile_download

Equipment for experiments with tilted samples

For measuring dynamic contact angles according to the tilting method, the solid sample has to be tilted from its horizontal position. Measuring the dynamic contact angle on a tilted sample directly yields the advancing, receding and rolling angle as well as the contact angle hysteresis of sessile drops.

TBA 360

The manual tilting base assembly TBA 360 is placed on top of the sample stage of an OCA model. With the manual turning mechanism the small stage can be freely rotated a full 360°.

TBU 100

The electronic tilting base units TBU 100 & TBU 100EC fully automatically tilt the entire OCA device in a range of -5° to +95° including attachments like dosing systems and environmental chambers. By tilting the entire system the position of the sessile drop within the optical axis does not change and analysing dynamic contact angles becomes even easier.

• TBU 100 for the OCA models 25, 50 & 50EC as well as 200
• TBU 100EC for the OCA model 15EC

The TBU 100/100EC can be controlled via the TP 50 control panel and the OCA software.

Electronic turn table with vacuum fixation ETT/VAC

The electronic turn tables with vacuum fixation ETT/VAC facilitate the mapping of silicon wafers. They allow to access any position for contact angle measurements, even on 12″ wafers. The ETT/VAC features a connection socket for a vacuum pump and can be equipped with different sized top plates:

• WTP 6/VAC – wafer top plate for 6″ wafer
• WTP 8/VAC – wafer top plate for 8″ wafer
• WTP 12/VAC – wafer top plate for 12″ wafer

Single fibre, film and paper holders

Various different holders allow for a secure fixation and easy positioning of films, papers and even single fibres.

FHO 40plus

The single fibre holder FHO 40plus can securely span fibres of any thickness and with a length ranging from 25 mm to 70 mm with adjustable tension. Additionally the inclination and position of the fibre can be adjusted with manual axes.

FSH 30

The thin film sample holder FSH 30 is made of Delrin and is especially designed for thin films and foils. It consists of:

• base holder D = 30 mm
• clamping ring D = 30 mm (for very thin foils and membranes)
• clamping ring D = 30.1 mm (for foils < 50 μm)
• clamping ring D = 30.2 mm (for foils < 100 μm)

FSC 80

The film and paper holder FSC 80 can be used to span thicker films or papers with adjustable tension. The maximum usable sample dimensions are (LxWxH):

• 80 mm x 80 mm x 3 mm

Sample tables

The standard sample table of any OCA model can be replaced with optional specialised sample tables for easier handling of various sample types.

STC 100

The sample table STC 100 features holding clamps that reliably and easily fix flat samples like glass slides. The use of the STC 100 is recommended when working with the TBU 100.

SP 100

The suction plate SP 100 is designed to hold especially thin and flexible samples flat against the table using an adjustable suction area. The SP 100 comes with a connection socket for a vacuum pump.

FHM 100

Films or fabric can be spanned over the curved sample table FHM 100 and to which they are fixed with lateral magnetic bars.

Sample vessels and test pieces for lamella method

For the lamella method DataPhysics Instruments designed special sample vessels and test pieces. The test pieces TPL feature a connector for attachment to a glass syringe of the type DS xx/GT and a sphere of different diameters at the other end. In combination with the special sample vessels SVL with different diameters a lamella of for example molten solids can be pulled out of the vessel and analysed via software. Available test pieces and sample vessels:

• TPL-3.0 – sphere-⌀: 3.0 mm
• TPL-4.0 – sphere-⌀: 4.0 mm
• TPL-4.5 – sphere-⌀: 4.5 mm
• SVL 12/30 – height: 12 mm, inner-⌀: 30 mm
• SVL 12/50 – height: 12 mm, inner-⌀: 50 mm
• SVL 12/70 – height: 12 mm, inner-⌀: 70 mm
• SVL 24/30 – height: 24 mm, inner-⌀: 30 mm

Glass cells

The interfacial tension between two liquids according to the pendant drop method and the contact angle of a liquid drop or gas bubble according to the captive bubble method can be measured using glass cells made of special optical glass. The glass cells are usable at up to 70 °C or in a high temperature version at up to 350 °C. The glass cells are available in the following sizes (LxWxH):

• GC 10 – 20 mm x 20 mm x 20 mm
• GC 40 – 40 mm x 40 mm x 40 mm
• GC 50 – 20 mm x 50 mm x 20 mm

Sample holder for captive bubble measurements

The sample holder SHC 20 for captive bubble measurements fits into a glass cell GC 50 and allows for a flat attachment of samples during captive bubble experiments. Together with the glass cell and a specially bent needle SNC xx a gas bubble can be dosed beneath the sample holder.

Contact lens supports

With the contact lens supports CL 20 and SCL 21 contact lenses can be held inside a glass cell for captive bubble experiments. The SCL 21 features adjustable inlet pieces with three different radii of curvature to attach especially soft contact lenses without deformation of the shape.

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Optical standards OCAS

DataPhysics Instruments provides several sets of optical standards for the validation/verification of the OCA performance. Each glass slide features a standard sessile, pendant drop or lamella contour for image capture and subsequent analysis.

The comparison of the measured contact angle, surface or interfacial tension with the one stated on the slide is a crucial factor in the evaluation of instrument performance and reliability. All slides are manufactured with the highest precision, as per ISO 9001, in a controlled photolithographic process to serve as reliable references for the precision of measured data.

The OCAS basic set consists of two standard sessile drop shapes and one standard pendant drop shape. Various other shapes are available as well.

Topview Video System TVS

The Topview Video System TVS opens up a completely new approach to contact angle measurement. With this system deposited drops are monitored and evaluated in topview which allows to investigate previously inaccessible sample spots, for example, at the bottom of indents of ready-made components or on assembled printed circuit boards. Moreover, the TVS enables the determination of surface homogeneity and surface isotropy.

The Topview Video System TVS comprises an electronic syringe module which is used to dose a liquid drop with a well-defined volume via a bent needle. The drop is observed from the top by a camera with high resolution optics. If desired the already existing optics and camera of the OCA model can be mounted on the TVS holding system. For sample illumination two different systems are available which ensure an optimal contrast of the drop image depending on the reflectivity of the surface:

• TVS-R with LED ring light
• TVS-C with collimated coaxial illumination

Subsequent image processing of such contrast optimised pictures with the OCA software is of course easily feasible.

Topview brochurefile_download

Control panel with touch screen and precision control wheel

The TP 50 control panel with touch screen and precision control wheel establishes a comfortable and intuitive control of all electrical components of the OCA series, ranging from the electrically driven sample table over the electronic dosing systems up to any additionally attached modules such as a humidity generator. The precision control wheel allows to make settings exceptionally fast and still with the highest accuracy.

(The TP 50 control panel is included with an OCA 50 or an OCA 200)

Top view observation video system TV-VS

All OCA models can be equipped with the top view observation video system TV-VS. The TV-VS is mounted above the OCA main camera and provides an alternative view of the positioning of the dispensed drops on the surface. Hence, a solid documentation of the sample mapping is guaranteed. The TV-VS features an USB camera with high performance 6-fold zoom lens and adjustable observation angle.

Electro wetting platform EWP 100

The electro wetting platform EWP 100 is designed to investigate the influence of an electric field on the wetting and adsorption behaviour of modern, engineered materials. The EWP 100 facilitates the analysis of sessile and pendant drops in a defined electric field.

It features electrodes integrated into the top and bottom plate and connectors to a standard external lab voltage supply. With different spacer elements the distance between the electrodes can be adjusted.

Systems for investigation of oscillating drops

By analysing the shape of oscillating pendant drops, additional parameter like the surface or interfacial compression modulus, surface or interfacial dilatation elasticity and the surface or interfacial dilatation viscosity can be determined. DataPhysics Instruments offers two systems to generate oscillating pendant drops.

Electronic syringe module for oscillation ESr-O

The electronic syringe module ESr-O is designed for creating sinusoidal oscillating and relaxing pendant drops. The ESr-O is placed inside a syringe module carrier of a manual or electronic direct dosing system. The ESr-O features the following technical specifications:

• frequency range of drop oscillation: 0…20 Hz (viscosity dependent)
• harmonic volume (area) mode: typically 5…20 μl constant part, dV = 0…20 μl (for viscosities < 50 mPas)

Oscillating drop generator ODG 20

The oscillating drop generator ODG 20 utilises a piezoelectric actuator to create an oscillating pendant drop. Due to the high performance actuator the ODG 20 is able to create higher oscillation frequencies and can even oscillate the drop shape without changing the drop volume. The ODG 20 features the following technical specifications:

• frequency range of drop oscillation: 0…25 Hz (viscosity dependent)
• harmonic volume (area) mode: typically 5…20 μl constant part, dV = 0…20 μl (for viscosities < 50 mPas)
• constant volume (area) mode: max. 1…2 mm axis-symmetric drop shape oscillations (viscosity dependent)

Liquid injection system LIA-MD

The liquid injection system LIA-MD allows the addition of a second liquid into an existing pendant drop. Via a second electronic syringe module the second liquid is being injected directly into the pendant drop. By injecting surface-active or chemically reactive phases the relaxation of the pendant drop back into its equilibrium state is indicative of the reactivity of the liquids under study. The LIA-MD consists of:

• one syringe module carrier with fine adjustment screws for the axial and horizontal needle positioning
• second syringe module carrier inclined 30° for axial and inclined positioning with fine adjustment screws
• two connection cables

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