3dp_3ds_pennstate_penn_logoPenn State University has been responsible for some major advances in research, with members of both the faculty and the student body producing incredible work in, among many fields, 3D technologies. Partnerships with leading companies and proximity to high-tech facilities allow for continued growth in studies at this prestigious institute, which is behind a number of advances. As quickly as news continues to pour in from this university, the latest offers a look at something even quicker — an advance set to increase the speed of both 2D and 3D printing processes. Not just any speedy enhancement, the team from Penn State is researching a technique that can increase printing speeds by up to a thousand times.

“A major technological advance in the field of high-speed beam-scanning devices has increased the speed of 2D and 3D printing by up to 1000 times, according to researchers in Penn State’s College of Engineering,” Rebekka Coakley writes at Penn State News.

Three order increase in scanning speed of space charge-controlled KTN deflector by eliminating electric field induced phase transition in nanodisordered KTN,” recently published in Nature Scientific Report, offers insights into the research team’s processes and findings. The research was led by electrical engineering professor Shizhuo (Stuart) Yin, working with Robert Hoffman from Maryland’s Army Research Laboratory as well as Penn State graduate students Wenbin Zhu, Ju-Hung Chao, and Chang-Jiang Chen.

ktn-crystal-phases

The paper’s fairly dense abstract explains the project:

“In this paper, we report a three orders-of-magnitude increase in the speed of a space-charge-controlled KTN beam deflector achieved by eliminating the electric field-induced phase transition (EFIPT) in a nanodisordered KTN crystal. Previously, to maximize the electro-optic effect, a KTN beam deflector was operated at a temperature slightly above the Curie temperature. The electric field could cause the KTN to undergo a phase transition from the paraelectric phase to the ferroelectric phase at this temperature, which causes the deflector to operate in the linear electro-optic regime. Since the deflection angle of the deflector is proportional to the space charge distribution but not the magnitude of the applied electric field, the scanning speed of the beam deflector is limited by the electron mobility within the KTN crystal. To overcome this speed limitation caused by the EFIPT, we propose to operate the deflector at a temperature above the critical end point. This results in a significant increase in the scanning speed from the microsecond to nanosecond regime, which represents a major technological advance in the field of fast speed beam scanners. This can be highly beneficial for many applications including high-speed imaging, broadband optical communications, and ultrafast laser display and printing.”

figure-2

From the paper: (a) An illustration of an EO KTN crystal based switchable half-wave plate. (b) The experimentally measured response time of the refractive index change of the KTN crystal as a function of the applied electric field at 26 °C (red) and 31 °C (black).

Whew. To break this down a bit, it’s important first to note that a KTN beam deflector is essentially a crystal, made of potassium tantalate and potassium niobate (or potassium tantalate niobate, abbreviated as KTN), with a large electro-optic effect. The researchers found that at higher temperatures than previously used, a nanodisordered KTN crystal’s electric field-induced phase transition can be eliminated. The Curie point is the “temperature at which certain magnetic materials undergo a sharp change in their magnetic properties,” explains the Encyclopædia Britannica. Exceeding not only this temperature point but also the critical end point (defined as “the set of conditions under which a liquid and its vapour become identical”), the team discovered that scanning speeds were sped up dramatically.

“Basically, when the crystal materials are applied to an electric field, they generate uniform reflecting distributions, that can deflect an incoming light beam. We conducted a systematic study on indications of speed and found out the phase transition of the electric field is one of the limiting factors,” explained Dr. Yin.

Speeds of scanning then move from the range of microseconds up to nanoseconds. The team noted that this offers speed enhancements to printing (both 2D and 3D), ultrafast laser display, high-speed imaging, and broadband optical communications. To put this speed into perspective, Dr. Yin explained that 20,000 pages 2D printed would take just one minute — while a previously one-hour 3D printing job could be cut down to seconds.

“The optical beam deflector is widely adopted in many fields including imaging, printing, sensing, displays, and telecommunications,” the researchers state in their paper, pointing to the myriad applications set to benefit from this study.

figure-3

From the paper: (a) An illustration of the experimental setup used to measure the response time of the space charge-controlled KTN beam deflector. (b) The experimentally measured response time of the space charge-controlled KTN beam deflector at 26 °C (near the Curie temperature, the electric field-induced phase transition occurred) and 31 °C (well above the Curie temperature, with no electric field induced phase transition in this case).

Dr. Yin pointed out that medical applications in particular could see significant benefits, as high-speed imaging could be done in real time. Non-invasive imaging using light waves could be used during surgical procedures to produce live 3D images of patients, allowing for on-the-spot understanding and correction.

“In conclusion,” the researchers finish their paper, “we found that the electric field-induced phase transition plays a significant role in determining the scanning speed of a space charge-controlled KTN beam deflector. In the electric field-induced ferroelectric phase, although there could be an electric field-induced refractive index change, the refractive index change gradient remained constant as long as there was no change in the stored charge density. In this case, the response time of a KTN beam deflector is limited by the electron mobility in the KTN crystal even in the presence of the pre-injected and trapped electrons. Thus, for very high-speed nanosecond scale applications, one must avoid the electric field-induced ferroelectric phase by operating the KTN beam deflector at a temperature not only above the Curie point but also above the critical end point. This results in a three orders-of-magnitude increase in the scanning speed from the microsecond to the nanosecond regime; this represents a major technological advance in the field of high speed beam scanning devices. This improvement can be very useful for many applications such as high speed optical coherence tomography, ultrafast reconfiguration free-space optical communications, and ultrafast laser display and printing.”

For full details, you can read the entire paper here. Discuss in the 3D Print Speed forum at 3DPB.com.

[Source: Penn State]
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