Frequently Asked Questions

Frequently Asked Questions

Q1: Can you explain on-the-fly printing?

A: The phrase 'on-the-fly printing' refers to the continuous movement of the print head travels continuously during the printing process.  Arrayjet microarrayers use the Xaar XJ126 printhead, an industrially proven, 126-nozzle, shared-wall inkjet printhead that travels continuously at 20 cm.s-1 during printing.  This translates to a printing rate of approximately 475 features per second, or alternatively the capability to print an entire 384-well plate, in triplicate onto 100 slides in less than 25 minutes.

Q2: What is inkjet printing?

A: Inkjet printing is the ejection, from a nozzle, of liquid droplets which travel a short distance (1 – 5 mm) through the air to land on a substrate in a predetermined pattern.

Q3: What are Arrayjet's key benefits versus other printers?

A: There are many, the key benefits as follows:

Accuracy & reproducibility: low intra- and inter-slide CV values utilising Xaar piezoelectric printhead technology with <5% CV.  More specifically, this means:

  • No sample accumulation.  
    Samples are loaded directly into the print head via the JetSpyder so solutions do not clog the printing nozzles.  Over time, systems that dip the printing device directly into the sample will suffer sample accumulation, leading to clogged nozzles and variable print quality.
  • Nozzle accuracy.
    Arrayjet’s printing nozzles are made of thermoset polyimide.  The nozzle apertures are laser ablated through the polyimide layer giving superior nozzle accuracy.

Flexibility: the ability to print a variety of probes onto a wide range of substrates.  Users can define spot volumes from 100 pL to 10 nL with no restrictions on pitch.

Time saving: no time penalties or limitations to the number of samples printed simultaneously when printing multiple arrays on a substrate, i.e. it is as fast to print 16 or 96 well/pad substrates as it is a planar array.  This feature ensures Arrayjet printers utilise the fastest technology on the market.

Low running costs: robust, industrial-proven print head with no breakable tips or capillaries.

Economical sample usage: the JetSpyder, a unique sample loading device can be used in conjunction with the JetGuard to reduce dead volume, sample evaporation and sample waste.

High volume throughput: range of 5 instruments with an upper throughput of 1,000 slides printed in a fully automated run.

Modular, scalable technology: the same technology used on all Arrayjet platforms ensures capacity and throughput can increase alongside customer requirements.

Q4: What types of samples can Arrayjet microarrayers print?

A: Arrayjet systems are routinely used for printing the following samples:

  • Nucleic acid (oligos, PCR products, miRNA, PNA)
  • Proteins (including lectins, glycoproteins, and recombinant) peptides and antibodies
  • Cell and tissue lysates
  • Serum and plasma
  • Aptamers (nucleic acids and peptides)
  • Hybridoma culture supernatants
  • Carbohydrates and oligosaccharides
  • Nanoparticles and polymers

Q5: Do Arrayjet systems have the flexibility to print onto a variety of substrates?

A: Yes, Arrayjet microarrayers are highly flexible and can print almost any sample type onto any substrate.  Dedicated substrates holders exist for the following:

  • Glass slides
  • Membrane sheets (e.g. nitrocellulose, PVDF or nylon)
  • Two-part 96 well microplates (e.g. Schott Nexterion MTP)
  • Plastic microplates
  • We also routinely develop customer-specific holders for non-standard substrates

Q6: Can Arrayjet systems print into microplates wells? 

A: Yes, Arrayjet systems can print into microplates with wells up to 4 mm deep.  Standard Arrayjet-recommended plates have a working volume of 100 μl per well, and a printable area of 4 mm2.  These can be supplied in a variety of materials, colours and surface chemistries to match customer applications.  Alternatively, Arrayjet can help to develop plates and substrates to suit individual customer applications.

Q7: What's the smallest spot size Arrayjet can print?

A: 60 μm.  Spot size is a function of spot volume and the contact angle determined by the surface tension of the sample being printed and the relative hydrophobicity/hydrophilicity of the substrate.

Q8: How many arrays can I print with my sample?

A: From a single aspiration up to 6000 x 100 pL features of each sample can be printed.  A minimum of 5 μL sample is recommend in each well per aspiration. For example, this is sufficient to print:

  • 3 replicates of a 200 pL feature onto 1000 slides – printed in under 5 hours
  • 2x 100 pL replicates per well into thirty-one 96-well microtitre plates
  • A 300 pL feature in duplicate on each of 16 pads on 50 slides
  • If more replicates are required, the system will automatically aspirate more sample as required

Q9: Is sample evaporation a big problem with Arrayjet microarrayers?

A: No. Arrayjet systems are unique because they are compatible with the JetGuard™, a self-sealing silicon mat which creates a microclimate with 100% relative humidity around the sample, thus minimising evaporation. In-house experiments show that within the first hour, aqueous solutions can lose over 10% of their volume from unprotected 384 well plates; Arrayjet's JetGuard effectively eradicates this source of variability.  Arrayjet is the only microarray technology capable of using this feature, through which the JetSpyder liquid handling device can penetrate to access samples.

The JetGuard is also successful in protecting valuable samples from external contamination.

Q10: How has the Arrayjet technology developed over recent years?

A: With in-house development and manufacturing teams Arrayjet are able to continuously improve their technology.  Three key areas of development include:

1. Improving the user experience with a more modern graphical interface and software flexibility.

2. Developing manufacturing monitoring tools, including in-line process controls to monitor and combat system drift and minimise instrument down-time.

3. Expanding the range of supported application, including: microplate printing, a range of glycerol-free buffers for covalent immobilisation, low temperature printing, reverse phase protein arrays and CMOS chip printing.

Q11: Do I have to use Arrayjet printing buffers?

A: No. Arrayjet has developed a range of printing buffers which are compatible with the technology and produce high quality, consistent arrays with excellent spot morphology.  Arrayjet customers are not limited to these buffers and the in-house development team can guide customers with assay-specific requirements, either suggesting suitable formulations or developing a specific buffer via the assay development service.

Arrayjet systems use a specially formulated hydraulic fluid to drive all of the liquid handling operations and to clean the system between sample sets.

Customers have access to all Arrayjet buffer formulations and protocols with the option to prepare them in-house, or purchase pre-prepared volumes.

Q12: Can I print samples containing high concentrations of glycerol?

A: Yes. Many biological samples are stored or supplied in solutions containing glycerol and the Arrayjet systems handle them effortlessly.

Q13: Do I have to add glycerol to my samples?

A: No. Arrayjet have developed glycerol-free printing buffers which are particularly useful for covalent immobilisation.   Customers have access to all Arrayjet buffer formulations and protocols with the option to prepare them in-house, or purchase pre-prepared volumes.

Q14: Will piezoelectric printing heat up my samples?

A: No. There is no heating generated during the Arrayjet printing process.

Piezoelectric printing induces an acoustic wave which initiates droplet ejection.  The interior walls of the Arrayjet printhead are made from the ceramic material lead zirconate titanate (PZT).  When PZT is subjected to an electrical charge it changes shape, causing a volumetric change and a subsequent acoustic wave that ejects a droplet of sample from the nozzle.  There is no heating of the sample and no mechanical stress on the printhead; nozzles consistently print even after actuations exceeding 10e13 per nozzle making this technology ideal for printing reliable microarrays.

Piezoelectric printing is sometimes confused with thermal inkjet, also known as bubble-jet, which uses the rapid heating of samples to create a pocket of gas to induce the required pressure for droplet ejection; this is not used by Arrayjet.