Monthly Archives: July 2015

The $30 Million Airway Fire And The Wisdom of Certifying Medical Laser Safety Officers

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If there’s one image that stays with you after the International Laser Safety Conference, it’s an image of the blowtorch effect caused by a laser striking an oxygen-filled endotracheal tube.

Screen grab from a YouTube video showing an endotracheal tube being set afire by a CO2 laser. (Click image to watch video).

Another powerful visual is imagining a concerned — and empowered — laser safety officer walking away from a potentially dangerous operating room situation if a laser surgery seems about to go awry.

Yet another indelible image is picturing a 53-year-old grandmother undergoing a routine 10-minute laser procedure to remove vocal cord polyps — only to have her airway seared after a series of apparent educational and procedural lapses.

Some might say pointing out such dire occurrences is merely an attempt to frighten or be provocative. But there’s really no way to make an inherently horrific occurrence like an airway fire any scarier than it is.

Perhaps more worrisome is the fact that so many more medical LSOs should be certified to take the reins of laser safety in health-care facilities large and small. The need is evident as lasers grow in importance as a surgical and therapeutic tool.

Further evidence of the need for certified medical laser safety officers was provided by attorney Matthew Wojcik of Seattle firm Bullivant Houser Bailey, who detailed the 2012 case of the aforementioned 53-year-old Washington state woman who eventually died from injuries sustained from an airway fire that started about eight-and-a-half minutes into her surgery. According to Wojcik, who represented the laser manufacturer, the surgeon, anesthesiologist and “laser safety nurse” all testified to varying degrees of understanding or even awareness of hospital laser safety protocols, their application and the laser safety committee’s role.

With no CMLSO in place, potential red flags during the procedure — including the laser being set to 18 watts and the oxygen not being turned down from 100 percent to around 30 percent — went unheeded. In fact, the hospital’s previous LSO had left about two years before the incident.

Ultimately, the hospital reached a $12 million settlement with the patient before trial; the patient was awarded $18 million after a trial. (The laser manufacturer was dismissed from the lawsuit prior to trial; the maker of the endotracheal tube was spared from blame in the trial.)

And to think that it might only have cost about $3,500 to properly train and certify a CMLSO who could have been empowered enough to notice anomalies in the procedure and address them — or even postpone the surgery.

It seems hard to argue that the added insurance of naming, training and certifying a CMLSO is worth the cost, given the potentially severe toll a laser surgery gone wrong might take.

A quick look at the list of dozens of CMLSOs certified by the Board of Laser Safety shows that many facilities across the U.S. are committed to investing in the soundness of laser policies and procedures. And yet, a recent survey by UHS Surgical Services indicated that about 40 percent of the 266 health-care facilities responding did not have an LSO or safety program in place.

Where do you stand? Is certifying a medical LSO essential or a luxury?

Geoff is LIA’s communications director. Contact him at ggiordano@lia.org to share your experiences with lasers, sound off on issues regarding any facet of laser technology, suggest stories or offer your commentary with a guest article or blog post.

Read more details on the case and verdict here.

Non-Tenure Track Job Opportunity in Laser-Assisted Nano Engineering laboratory at University of Nebraska-Lincoln

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The Laser-Assisted Nano Engineering laboratory in the Department of Electrical & Computer Engineering at the University of Nebraska–Lincoln is seeking a qualified individual to fulfill a non-tenure track Research Associate Professor Position on one-year fixed-term basis (10/01/2015 to 09/30/2016), with the possibility of renewal based on performance and available funding.

Applicants should possess a Ph.D. in physics, materials science and engineering, or a closely related field, and at least three-year research-faculty experience in two-photon polymerization micro/nano-fabrication, laser-assisted diamond growth, laser-assisted GaN deposition, and laser-assisted carbon nanostructure fabrication (such as carbon nanotubes, carbon nanoions and graphene).

The appointee is expected to conduct frontier research in laser-assisted material synthesis and micro/nano-fabrication, engage intensively in lab management, grant application, and graduate student mentoring, and be responsible for quality teaching in relevant subjects at undergraduate or postgraduate levels.

Formal applications must be submitted online at this link: https://employment.unl.edu/postings/45696. Search for Research Associate Professor Electrical and Computer Engineering (Requisition Number F_150116). Applicants should provide the following documents as separate files: (1) a letter of application, (2) curriculum vita, (3) statement of research interests, and (4) names and contact information for at least three references. Screening of applicants will begin on August 20 2015.

Laser Safety Community Focused on Safeguarding Consumers Who Are Attending Light Shows and Acquiring Pointers

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A December 2013 laser light show in France. Source: Wikipedia Commons/Kergourlay

By Geoff Giordano

With plenty of summer left to enjoy, it is appropriate to remind revelers to be aware when attending outdoor laser demonstrations or using handheld laser pointers. More and more handheld laser pointers are being sold to consumers and tourists — especially online — and they often exceed the output power listed on the label.

As lasers continue to break new ground as tools of healing, communication and entertainment, knowing how to avoid beam-related eye and skin injuries is paramount. New research illustrates the need for consumers to use caution and be aware of potential dangers.

A study presented at LIA’s International Laser Safety Conference in March warned of the dangers laser pointers present to youths. The study, led by U.K. ophthalmologist Fahd Quhill and related by ILSC General Chair John O’Hagan of Public Health England, presented cases of permanent eye damage suffered by five children in Sheffield, England. Consumer lasers given as gifts or acquired from websites, tourist destinations or modified commercial products cost some of those children more than 50 percent of their vision.

“What do you do” when a laser-related eye injury suffered by a youngster “wipes out the possibility of a whole range of career opportunities (for them)?” O’Hagan asked.

One move toward a solution came in February 2014 with a decision by the European Commission to put controls on laser products intended for consumers. According to O’Hagan, the decision indicates that “child-appealing products shall not cause damage to the eyes or skin in case of any exposure that could occur under any conditions of use, including deliberate, long-term exposure with optical viewing instruments.” The broadly applicable statement also helps regulate products intended for home hair removal. The decision allows the manufacture of products “that can do something to the skin providing (they) can’t harm the eye,” O’Hagan explained.

Meanwhile, increasingly popular laser light displays at concerts and festivals can pose a danger to spectators from unintended exposures to the laser source. Peter Blattner of the Swiss Federal Institute of Metrology (METAS) discussed the agency’s real-time assessment of laser shows and potential irradiation of spectators. The system was tested successfully in the field at about 20 laser shows in Switzerland, those tests often mandated by regulators or show operators. The tests found that all the shows exceeded maximum permissible exposure limits, Blattner said — some by up to 120 times those limits. The shows were adjusted to acceptable levels.

The challenge with laser light shows, said James Stewart of LVR Optical, is that “one minute they are quite smooth and fluid beams, the next minute they can (become) very stationary for a few milliseconds — enough time to create these accentuated, tight finger beams of light.”

Stewart and Blattner noted the prevalence of lower-cost laser projectors available to show organizers.

“As far as nightclubs go,” Stewart explained, “the entry-level (power) is three watts.” He notes that many people who attend his training sessions after recently purchasing a three-watt or five-watt laser for light shows “become a bit disillusioned” when they learn they can’t use the system to scan the crowd in their small venue.

In larger-scale uses, laser systems are typically eight to 30 watts, Stewart said, but typically only one to three watts would be used to scan an audience. He has been involved in assessing audience-scanning laser light shows presented by major global recording artists when they performed in the U.K. Even a one-watt laser will be hazardous at around 200 meters, he noted.

While show presenters can alter the laser beam to be less harmful to audiences, to avoid injury at shows, it is generally advisable not to intentionally stare or look at where the laser beam is coming from.

As O’Hagan pointed out, in some cases people struck in the eye by a beam from a handheld laser pointer were not injured by the beam but from rubbing their eyes after the fact.

To help inform the public, LIA created a primer on laser pointers and tips for using them safely. The guidelines are intended to be shared freely in the hopes of helping avoid accidents.

LIA advises the following in regard to laser pointers:

  • Never shine a laser pointer at anyone. Laser pointers are designed to illustrate inanimate objects.
  • Do not allow minors to use a pointer unsupervised. Laser pointers are not toys.
  • Do not point a laser pointer at mirror-like surfaces. A reflected beam can act like a direct beam on the eye.
  • Do not purchase a laser pointer if it does not have a caution or danger sticker on it identifying its class. Report suspicious devices to the FDA.

Geoff is LIA’s communications director. Contact him at ggiordano@lia.org to share your experiences with lasers, sound off on issues regarding any facet of laser technology, suggest stories or offer your commentary with a guest article or blog post.

Report of 11 laser strikes on jetliners over N.J. illustrates continued threat posed by misuse of green laser pointers

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By Geoff Giordano

As word came in from the Federal Aviation Administration that 11 jetliner crews reported being struck by green laser pointers over New Jersey — five of them near Newark Liberty International Airport — I was instantly reminded of some solutions to such potentially devastating acts that were discussed at our International Laser Safety Conference in March.

As evidenced by this latest occurrence — made more startling because Newark Liberty is tucked in amid a densely populated area — there is a reason ILSC 2015 featured at least a half-dozen presentations on the dangers of inappropriate laser pointer use. Laser pointers that strike the cockpit of a plane can temporarily blind a pilot or prevent the pilot from seeing past the glare.

Patrick Murphy, executive director of the International Laser Display Association and founder of the website LaserPointerSafety.com, suggested improved consumer labeling of handheld laser devices. Such “laser safety facts” labeling would make laser hazards more evident, similar to the way nutrition labeling informs consumers.

Current labels “were designed for experts back when lasers were expensive and bulky,” Murphy said. “What does ‘Laser (Class) 2’ mean to a consumer? There’s also no warning on any current labels against aiming at aircraft. People don’t know it’s hazardous (and) they don’t know it’s illegal.” The labels he proposes not only would more clearly state the dangers of pointing handheld laser devices, but they would also facilitate convictions of offenders “if the user has been specifically warned not to aim at aircraft.”

In terms of locating offenders, Trevor Wheatley of The University of New South Wales in Canberra, Australia, stressed the need for a low-cost, “always-on” method for locating the origin of these laser strikes. Wheatley detailed recent research into detection technology using cameras that could be installed on approach paths to commercial or military airfields and send reports to authorities for enforcement. “Education doesn’t seem to be working, banning doesn’t seem to be working, so we thought (in terms of) deterrence, where we increase the chances of (offenders) being caught,” Wheatley explained.

It’s worth noting that about 11 laser pointer strikes on aircraft are reported nightly across the U.S.; the FAA has reported nearly 4,000 such incidents annually in the U.S. since 2011. President Barack Obama in 2012 signed into law strict penalties for such incidents.

It’s also worth noting that these readily available green laser pointers present a further danger on the ground, particularly to youths. A study led by U.K. ophthalmologist Fahd Quhill and related by ILSC 2015 General Chair John O’Hagan of Public Health England presented cases of permanent eye damage suffered by five children in Sheffield, England. Consumer lasers given as gifts or acquired from websites, tourist destinations or modified commercial products cost some of those children more than 50 percent of their vision.

According to a 2010 article by Peter Derenski in Boeing’s Aero magazine, “The human eye sensitivity peaks in the green range and perceives green 30 times brighter than red. When comparing a green and a red laser of equal power output, the green one will appear much brighter than the red.”

At present, laser pointers with output power under 5 milliwatts are legal for sale in the U.S. But “even a ‘legal’ (in the U.S.) 5 milliwatt laser pointer can be a potential hazard if the light distracts or temporarily flashblinds a person such as a pilot,” Murphy notes on his website. “This is why you never aim a laser pointer at an aircraft or the driver of a vehicle.

LIA’s bulletin on laser pointer safety advises the following in regard to laser pointers:

  • Never shine a laser pointer at anyone. Laser pointers are designed to illustrate inanimate objects.
  • Do not allow minors to use a pointer unsupervised. Laser pointers are not toys.
  • Do not point a laser pointer at mirror-like surfaces. A reflected beam can act like a direct beam on the eye.
  • Do not purchase a laser pointer if it does not have a caution or danger sticker on it identifying its class. Report suspicious devices to the FDA.

Geoff Giordano, LIA’s director of communications, is based in northern New Jersey not far from Newark Liberty International Airport.

Ultra-short Pulse Laser Processing of CFRP with Kilowatt Average Power

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By: Christian Freitag1,2, Margit Wiedenmann1, Jan-Philipp Negel1, André Loescher1, Volkher Onuseit1, Rudolf Weber1, Marwan Abdou Ahmed1, Thomas Graf1

In order to process Carbon fiber reinforced plastics (CFRP) with a satisfying productivity, average laser powers >1 kW are necessary. Usually high average laser powers are achieved using continuous wave (cw) laser systems but the appearance of thermal damage ranging from 50 µm to several mm was observed using cw lasers for CFRP processing. According to model predictions the absorbed intensity has to be larger than 108 W/cm² to achieve a thermal damage smaller than 10 µm. Today such high intensities are conveniently achieved with ultra-short pulse laser systems. However, the average laser power of such laser systems is usually too low for productive cutting processes. The IFSW thin-disk multipass amplifier allows for the first time ultra-short pulse laser processing of CFRP at an average laser power of 1.1 kW with pulse energies of 3.7 mJ.

Fig. 1. A sketch of the experimental setup is shown.

Experimental setup

A sketch of the experimental setup used in this study is shown in Fig. 1. The laser source is a thin-disk multipass amplifier for 8 ps pulses with a maximum used average output power of 1100 W. The laser has a constant pulse repetition rate of 300 kHz which gives a maximum pulse energy of about 3.7 mJ. The laser emits at a wavelength of 1030 nm with a beam quality factor M² < 1.4. A fast scanner system was used leading to a maximum feed rate of the laser beam of 30 m/s. The resulting focal diameter was calculated to be about 125 µm (1/e² intensity level). The CFRP samples used were Toray T700S-12k carbon fibers with a RTM 6 matrix which is a monocomponent resin. The samples were processed by ablating on a circular path with a diameter of 50 mm in a multi-pass process.

Heat accumulation effects as a limitation

The heat affected area, where the matrix material is vaporized leaving blank carbon fibers, is called matrix evaporation zone (MEZ). The extent of the MEZ for different feed rates of the laser beam after 15 and 50 scans can be seen in Fig. 2. For both number of scans the extent of the MEZ becomes larger with decreasing feed rate. This is a consequence of the pulse-accumulation effect. Each laser pulse contributes to the heating of the processed material. This accumulation results in additional matrix damage if the temporal delay between consecutive pulses is too short for the material to cool down to almost its initial temperature. To limit the influence of the pulses-accumulation effect, the number of pulses applied at one spot should be reduced by choosing a high feed rate up to complete separation of the consecutive laser pulses.

Beside the pulse-accumulation effect, the scan-accumulation effect can also be observed in Fig. 2.  For

Fig. 2. The extent of the MEZ is shown for different feed rates at 1.1 kW average laser power after 15 and 50 scans.

an increasing number of scans, here from 15 to 50 scans, the MEZ increases significantly especially for low feed rates. The scan-accumulation effect is a major damaging mechanism when cutting CFRP with high average laser powers using a multipass process. Like the pulse-accumulation effect it also contributes to the increase of temperature in the compound but on a slower time scale. A characteristic parameter of the scan-accumulation effect is the number of scans above which the scan-accumulation effect causes additional matrix damage. The scan-accumulation damage develops, if a critical number of scans Ncritical is exceeded. Below this threshold, matrix damage is primarily caused by single-pulse damage or by the pulse-accumulation effect as can be seen in Fig. 2 for 15 scans. Above the critical number of scans, the matrix damage is mainly caused by the scan-accumulation effect as it is the case for 50 scans.

Cutting CFRP with high quality and high productivity

Fig. 3. Images of a cut in CFRP. a) Top view of the cut. b) Microscope image of a cross section of the cut. c) Magnified microscope image of the right, inner part of the cut. CFRP has been cut with a thermal damage smaller than 10 µm.

A rectangular shaped CFRP part was cut with 1.1 kW average laser power. To avoid the pulse-accumulation effect, a feed rate of 30 m/s was chosen. The influence of the scan-accumulation effect was reduced by a long cutting contour of 640 mm which increases the temporal delay between two consecutive scans. However, the scan-accumulation effect could not be completely avoided. Therefore, after each 200 scans, which are for this contour length still below the critical number of scans, a break of about 1 minute was implemented. The duration of this break was not yet optimized and is certainly much too long. The laser could be used for other processes during this break to further improve the productivity.

A view from the top on the cut work piece can be seen in Fig. 3a). It is noted that the gap between the inner and outer part does not represent the actual ablated kerf width. In total about 2100 scans where necessary to completely cut the material. With the applied feed rate of 30 m/s the effective average cutting speed was 0.9 m/min. By further optimization of the cutting process e.g. by ablating multiple parallel lines to increase the kerf width, an additional improvement of the effective cutting speed may be achieved.

The achieved quality of the cut can be seen in Fig. 3b) in a cross section. The inner part of the cut rectangle is shown on the right side while the outer part can be seen on the left. In Fig. 3b) some damage in the range of 200 µm is seen on the outer part.  In Fig. 3b) and in the magnification of this part in Fig. 3c) it can be seen that the inner part of the cut has no measureable thermal damage.

Conclusion

A novel ultra-short pulse laser system with an average laser power of 1.1 kW, 8 ps and 300 kHz was used to process CFRP.

Ablation experiments in CFRP with different feed-rates revealed the impact of the pulse-accumulation effect on the formation of the matrix evaporation zone (MEZ). For lower feed rates and therefore higher pulse overlaps the MEZ increases. A very important influencing factor on the MEZ formation is the scan-accumulation effect. This effect can lead to a burning of the matrix material and therefore to vast thermal damage. A characteristic value for the scan-accumulation effect is the critical number of scans above which the extent of the MEZ starts to increase very rapidly.

To demonstrate the capabilities of the used innovative laser source, CFRP has been cut with an effective average cutting speed of 0.9 m/min and no measureable thermal damage on the inner part of the cut rectangle.

 

 

1 Institut für Strahlwerkzeuge IFSW, Universität Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany

2Graduate School of advanced Manufacturing Engineering GSaME, Universität Stuttgart, Nobelstraße 12, 70569 Stuttgart, Germany