A holographic technique for imaging electric fields in the vicinity of toner microparticles

May 23, 2014
Figure 1: A scanning electron microscopy image of positively charged toner particles (yellow) on a polystyrene carrier particle (cyan). Credit: American Institute of Physics

Electrophotography techniques such as laser printing or photocopying involve the transfer of charged microparticles of toner or ink onto a rotating drum using electric fields. The microscopic electrostatic interactions between these particles and the drum greatly affect the print quality. Visualizing the electric fields around these charged particles, however, is difficult due to the small size of the particles and the complexity of their arrangement.

A research team led by Toshiaki Tanigaki and colleagues from the RIKEN Center for Emergent Matter Science has now demonstrated a holographic imaging technique that can map the electric fields around such complex systems of charged particles at microscopic scales.

Tanigaki and his co-workers used an known as split-illumination electron holography (SIEH) to study toner particles 5 micrometers in diameter attached to a carrier particle—a 38-micrometer polystyrene sphere (Fig. 1). The method involves splitting a beam of electrons into two separate paths; one beam passes near the toner microparticle and interacts with the in the particle's vicinity, while the other is preserved as a reference beam. The small electric fields around the microparticles become obvious when the probe beam is mixed with the reference beam to create a hologram. In this way, the team was able to compare the electrostatic potential in the vicinity of both positively and negatively charged toner particles.

The difficulty in such an experiment is ensuring that the reference electron beam is unaffected by the charged toner particles—a problem that has prevented accurate visualization of electric fields in such complex microparticle systems in the past. The setup used by Tanigaki and his co-workers overcomes this difficulty by diverting the reference beam sufficiently to avoid any influence from the toner particles. A second important consideration in the development of the SIEH technique was whether the incident beam of electrons would alter the charge on the polystyrene sphere. The team removed this potential source of interference by inserting a masking plate to ensure that the electrons passed near the toner and carrier particle without striking it.

The results of the SIEH experiment highlight the importance of charge transfer between the toner particles and the carrier, which alters the electric field in the region where the two meet. These findings, and the SIEH method itself, are expected to lead to improvements in the quality and resolution of electrophotography printing techniques. "We next hope to apply this technique to analyzing electric fields in other devices," says Tanigaki.

Explore further: Charge it: Neutral atoms made to act like electrically charged particles

More information: Tanigaki, T., Sato, K., Akase, Z., Aizawa, S., Park, H. S., Matsuda, T., Murakami, M., Shindo, D. & Kawase, H. "Split-illumination electron holography for improved evaluation of electrostatic potential associated with electrophotograpy." Applied Physics Letters 104, 131601 (2014). DOI: 10.1063/1.4869830

Related Stories

Patterns of particles generated by surface charges

February 4, 2014

Tuning the material structure at the nanoscale level can be really hard to achieve – but what if we had small particles, which assemble all by themselves, creating the required structure? At the Vienna University of Technology ...

The debut of the antihydrogen beam

March 7, 2014

The standard model of particle physics suggests that matter and antimatter are equal and opposite in every way. Yet the observable Universe is made almost entirely of matter—an asymmetry that remains one of the greatest ...

Heavy ions and lost resonance lines

March 21, 2014

Identifying the ns-np resonance lines in alkali-metal-like ions is an important issue in fusion plasma science in the view of spectroscopic diagnostics and radiation power loss. Whereas for n = 2, 3 and 4 these resonances ...

Using electron beams to encode data in nanocrystals

March 26, 2014

Ferroelectric materials have an intrinsic electrical polarization caused by a small shift in the position of some of their atoms that occurs below a critical point called the Curie temperature. This polarization can be switched ...

Recommended for you

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...

'Material universe' yields surprising new particle

November 25, 2015

An international team of researchers has predicted the existence of a new type of particle called the type-II Weyl fermion in metallic materials. When subjected to a magnetic field, the materials containing the particle act ...

Exploring the physics of a chocolate fountain

November 24, 2015

A mathematics student has worked out the secrets of how chocolate behaves in a chocolate fountain, answering the age-old question of why the falling 'curtain' of chocolate surprisingly pulls inwards rather than going straight ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.