Recycling Plastic Using Fluorescence Gets Green Light

Fluorescent light aids in quick sorting or recyclable plastics.

While recycling plastic is old news, innovative and efficient ways to sort plastics for recycling is always good news.

At the Ludwig-Maximilians-Universitaet (LMU) in Munich, researchers have developed a faster and easier way to identify and separate plastics (e.g., polyethylene terephthalate PET/PETE and polyvinyl chloride PVC) for recycling. The method uses a flash of light to cause the material to fluoresce.

LMU chemistry professor, Dr. Heinz Langhals had this to say:

Plastics emit fluorescent light when exposed to a brief flash of light, and the emission decays with time in a distinctive pattern. Thus, their fluorescence lifetimes are highly characteristic for the different types of polymers and can serve as an identifying fingerprint.

After photoexcitation, the plastic passes through a photoelectric sensor that measures the amount of illumination. This process determines the progress of the plastic’s decay. Polymers used in plastics show individual fluorescence lifetimes, therefore, the shape of the decay curve can detect it.

“Polymers represent an interesting basis for the sustainable cycling of technological materials. The crucial requirement is that the recycled material should be chemically pure,” Langhals said.

Purity Prevents Downcycling Waste

Polymers are processed as thermoplastics by melting at high-heat and injection molding to create the finished product. When recycling, the plastic is again exposed to high heat, which could change its properties if the sorted material is contaminated by another polymer. The material is then downcycled. Downcycling happens when a material loses quality or functionality in the process of recycling, but the end product can be used. Polymers don’t mix well with other polymers. Even a 5% contamination can drastically decrease the quality of the final product. This is why new high-quality plastics are always made from virgin materials, without the use of recycled materials at all.

The way for recycling plants to avoid downcycling is to try to achieve the highest purity when sorting the plastics.

“The waste problem can only be solved by chemical means, and our process can make a significant contribution to environmental protection because it makes automated sorting feasible,” Langhals said.

The novel method developed by the LMU team using fluorescence allows the sorting of up to 1.5 tons of plastic per hour. As a result, it already meets the mandatory requirements for industrial use and the creators will be applying for a patent on the new technology.

The specifics can be found in the journal Green and Sustainable Chemistry, where the group tested the technical polymers Luran® (styrene, polyacrylonitrile copolymer from BASF), Delrin® (polyoxymethylene from DuPont) and Ultramid® (polyamide with glass fiber from BASF).

The Here and Now

Current technology for sorting plastics for recycling include near-infrared spectroscopy that scans the plastics on a high-speed conveyor belt under the powerful light source. Some of the wavelengths are absorbed, and some reflected and captured by lenses. The lenses transmit a signal identifying the material to the shutter valves, and the material is blown into the appropriate chute. This video below gives a behind-the-scenes glimpse of a plant using NIR technology:

Sorting by hand is still very much in use today to separate plastics. Of course, this method allows for human error in the sorting, leading to downcycling.

The only way to save our “plastic planet” is through recycling. The more fast and efficient techniques we find to sort the materials, the better. Amazing things are being created with recycled plastics, like filaments for 3D printing, polyester fleece, and carpet. So, look out Pacific Ocean garbage patch we’re coming for you next. Who knows? There may be enough recyclable plastic out there to build the first recycled amusement park.

Image by belchonock/123RF.
Source: “Breakthrough Trial for Recycling Based on Fluorescent Light of Technical Polymers,” by Jenny Eagle,, August 26, 2014.
Source: “Novel Recycling Methods: Fluorescent Fingerprint of Plastics,” Science Daily,, August 21, 2014.
Source: “High Performance Recycling of Polymers by Means of Their Fluorescence Lifetimes,” by Heinz Langhals, et al., Green and Sustainable Chemistry, August 2014, DOI: 10.4236/gsc.2014.43019.

Printing Healing Polymers


A standard 3D printer, such as this one, was used to create the polymer drug-delivery implants.

3D printers are being used to create customized controlled drug-delivery implants for patients.

Imagine a 3D-printing technique that could produce a biological implant to transport therapeutic drugs directly to the intended area. Imagine the implant could deliver chemotherapeutic drugs to a tumor to destroy the cancerous tissue. Imagine that after the implant delivered the drugs to the intended target, it would simply degrade safely in the body and be expelled.

It seems a team of research faculty and doctoral students at Louisiana Tech University have let their imaginations run away with them.

Drug-Delivery Breakthrough

The research group from disciplines including the biomedical engineering and the nanosystems engineering programs have developed 3D-printed medical implants that can be loaded with antibiotics or chemotherapy drugs for a more-focused drug-delivery system. This breakthrough could generate improved drug-delivery implants and catheters.

The team created a medical-grade, biodegradable, and biocompatible 3D-printable bioplastic using a filament extruder. The filament extruder can take a polymer resin such as polylactic acid (PLA) or polycaprolactone (PCL) and turn it into a filament that can be used in 3D printing.

Ordinary Equipment

The implants can be printed as single beads, a string of beads, in disc form, or as a fiber. The beads were printed on a standard consumer 3D printer. The print time for the beads was approximately 1-3 minutes, and approximately 5 for the catheter. They are partially hollow to produce more surface area to carry an increased drug load if necessary. The device allows control over the amount of drug delivered to prevent damage to the liver or kidneys. The printing doesn’t stop there. David K. Mills, Ph.D., professor of biological sciences and biomedical engineering, told Polymer Solutions Newsblog:

We can also print syringes, catheters, etc., and all our anti-infective constructs can be loaded with gentamicin, kanamycin, nitrofurantoin — but the method can be extended to many other drugs, including methotrexate, etc.

The inspiration behind the creation of this novel 3D-printing technique was to develop a way to reduce infection, aid in cancer treatment, and to help prevent the spread of disease. The main idea was to freely produce beads and filaments that would reduce infection, as well as provide chemotherapeutic drugs, using a standard 3D printer. The emphasis of the design was based on controlled drug release as far as how much and when. The design would be able to support whatever drugs needed (i.e., antibiotics, antifungals, etc.) to prevent infection and to assist in the treatment for myelodysplastic syndromes (MDS), a bone marrow failure syndrome that typically affects the elderly. It would also be used as an application to treat specific diseases such as cancer.

Current technology employs the use of bone cement as the drug-delivery system. The process is more complicated as the surgeon has to mix the cement in the operating room. The drugs are stirred in and can vary in concentration. The bone cement is applied using a spatula and if trying to fill a weakness or fracture in the bone it doesn’t always fill the imperfection.

The bone cement contains methyl methacrylate (MMA),  a chemical intermediate in the manufacture of Plexiglass, and a possible carcinogen. It cannot be broken down by the body, therefore, a second surgery must be performed to remove the device. On the contrary, the degradation of the new 3-D printed implant inside the body eliminates the need for further surgery.

 Customized Treatment

The latest trend with doctors and pharmacists is the customization of medical products in the treatment of patients. This novel technology can offer them just what they need to deliver personalized care and targeted drug delivery for their patients.

Mills explained to Polymer Solutions Newsblog:

We have also developed a prototype of a 3D print gun. With a 3D scanner, we can image a bone defect, fracture, etc., and then using the scanned image and print gun, completely fill in the defect with resorbable drug-infused materials, bone cement, etc. The key feature here is that the scanned defect is filled in based on the image, and drugs are provided at the right dosage from top to bottom.

The ability to reproduce the design on a standard consumer 3D printer is an added bonus. “One of the greatest benefits of this technology is that it can be done using any consumer printer and can be used anywhere in the world,” said Jeffery Weisman, a Ph.D. student in Louisiana Tech’s biomedical engineering program and one of the researchers involved in the project.

The development of this new technology could revolutionize patient care in hospitals and clinics worldwide. Imagine a world where disease can be controlled by tiny beads and therapeutic drugs. Imagine a world where cancer can be cured. It could just be over that 3D-printed horizon.

Image by tomasmikula/123RF.
Source: “Louisiana Tech Researchers Use 3D Printers to Create Custom Medical Implants,” by Dave Guerin,, August 20, 2014.
Source: “3D-Printed Implants Infused With Medicine to Enable More Effective Drug Delivery,” by Nick Lavars,, August 21, 2014.
Source: “Researchers Develop Method for 3D Printing Chemotherapeutic Medicines on Desktop 3D Printer,” by Michael Molitch-Hou,, August 22, 2014.


Animal Parts From Your 3D Printer

3D-printed cart for Chihuahua born with no front legs.

The process of 3D printing and 3D printable polymers like polylactic acid (PLA) are making the world a better place. 3D printing is being used to help people and animals all over the world.

Print and Roll

Turboroo, a Chihuahua, was born with no front legs. Thanks to 3D printing, and the know-how and generosity of Mark Deadrick, Turboroo can walk — or rather, roll. Deadrick, president of 3dyn, a California-based industrial design and manufacturing company, came across Turboroo’s call for help online. Deadrick designed a customized cart based on the photos provided on the site and added a set of rollerblade wheels. Turboroo can now roll along with his new high-tech “legs.”

The design was 3D-printed using a MakerBot Replicator 2, using PLA filament at 1.75mm. The PLA comes in many colors (even glow-in-the-dark). The cart took approximately four hours to print using a 30% fill volume (a honeycomb structure is created by the printer). If it were a solid piece, it could take about 10-12 hours to print. In addition to the fill volume, the layer thickness is adjustable (it was set at .20mm/layer (.008″ per layer) for the cart.

Deadrick told Polymer Solutions Newsblog:

We typically compare materials to aluminum, which would run under $4 a pound for fabrication, but is at least three times as dense, and traditional machining would make you start a large chunk of material, and remove what you don’t want. 3D printing, for the most part, adds material only where you need it.

A Lame Duck With Lots of Pluck

Buttercup the duck was born with a deformed foot, which would often get cut up as the duck walked, leaving him in pain. So Mike Garey, Buttercup’s caretaker from Feathered Angels Waterfowl Sanctuary in Arlington, Tennessee, took a veterinarian’s advice and opted to have the foot removed. Garey worked tirelessly to find an appropriate prosthetic for his feathered friend. The first model was made using a 3D-printed mold to create a silicone foot for buttercup. Buttercup was able to walk again and was quite happy with his new appendage.

Garey, however, was not thoroughly impressed with the design he had created. It had limitations in movement especially when swimming. He wanted Buttercup to have the most advanced prosthetic he could design so he could be like other ducks. Since his first design, new materials called flex filaments had entered the market for 3D printing. Flex filaments are made from thermoplastic elastomers (TPE) a class of copolymers. The TPE material offered more flexibility to his design, and Garey was able to create a prosthetic that closely resembled a real duck foot. After hundreds of hours and many designs later, Garey created his newest prosthetic design.

Click on the video below to see the design and printing of Buttercup’s new foot, and you can see firsthand how happy Buttercup is running around!

Fly Like an Eagle

Beauty, a bald eagle, was shot in the face, destroying the upper part of her beak. She was found foraging for food in at a dumpsite in Alaska, but due to the condition of her beak she was starving.

Jane Fink Cantwell, a medic at Birds of Prey Northwest near Coeur d’Alene, Idaho, took Beauty in and nursed her back to health. She tried to contact experts in the field for advice on how to save Beauty, but they all had the same answer: Euthanize Beauty since it was impossible to fix her beak. While teaching a class in Idaho, Cantwell met someone who thought he could help. That someone was Nate Calvin, founder of Kinetic Engineering Group. Calvin had no experience in the field but thought he could help Beauty.

Cantwell, Calvin, a team of wildlife experts, and even a dentist worked together to create a beak to help Beauty. They examined Beauty and even took X-rays of her head to customize a beak for her. After the design was completed, Calvin used a 3D printer to build the prosthetic beak. The new beak was made from a nylon-based polymer specifically designed for 3D printing.

After a two-hour surgical procedure to attach the beak, the team worked to tweak it by filing, adjusting and testing until it finally worked. After the surgery Beauty could do the things a normal eagle could do, like groom herself and drink water.

Endless Possibilities

These are just a few of the amazing stories of how 3D printing has changed our world. The possibilities are endless as to what can be accomplished with this new and innovative technology. With the emergence of 3D printing technology, we’re now thinking outside the cube.

Image by Downtown Pet Vet | Mark Deadrick.
Video: “Buttercup the Duck’s New Foot Is Printed on a 3D Printer and He Walks & Runs!” by Feathered Angels Sanctuary,
Source: “TurboRoo, The Chihuahua With No Front Legs, Can Walk Again Thanks To 3D Printing,” by John Biggs,, August 8, 2014.
Source: “Buttercup the Duck Gets Brand New 3D Printed Foot,” by Alan Gardner,, February 24, 2014.
Source: “Beauty the Bald Eagle Gets a New 3D Printed Beak,” by Brooke Kaelin,, July 14, 2013.

Polymers Help Keep Us Footloose and Fancy-Free

Orthotics can be made of many types of polymers.There’s nothing wrong with giving your feet a little love. With the help of polymers like polypropylene and polyethylene, it’s easy to keep your puppies hushed.

What Makes Your Dogs Bark?

Our feet take us everywhere. Whether we drive, walk, jog, run, jump, rollerblade, or bike, we rely on our feet to get us where we need to go. What we don’t realize is how much weight and pressure our feet are under with every step we take. Physicists have estimated the impact of each step at 4.5 times your body weight for day-to-day activities, six times your weight when walking, and 20 times your weight for jumping. At a brisk walk, someone who weighs 200 pounds would be putting 1,200 pounds of pressure on each foot, or 4,000 pounds when jumping. This can be a serious shock to your feet, and if you carry extra weight, the strain is much greater. With all of this weight and pressure, it’s no wonder our tootsies ache at the end of the day.

Functionally Accommodating

We’re always looking for ways to make our favorite or stylish shoes more comfortable. One answer is the orthotic shoe insert. Orthotic inserts add a layer of extra shock support to help support your joints. They can be custom-made to assist with walking issues such as overpronation or oversupination. Overpronation occurs when weight is transferred from the heel to the forefoot and the foot rolls inward. Oversupination is the opposite, the foot rolls out, placing more weight on the outside of the foot.

When buying orthotics, there are many factors to consider, such as the need for the orthotic, i.e., whether it’s functional or accommodative. A functional orthotic focuses on biomechanics and can aid in correcting problems. These orthotics are usually custom-made using measurements taken by a doctor or professional. Accommodative orthotics offer comfort and protection with minimal correction of foot issues. These orthotics can be purchased in stores or online. Some accommodative orthotics can be used in conjunction with functional orthotics, though you should consult your doctor to be sure. The base materials used in the development of foot orthotics also play a role in the purchase.

Polymers, Leather, and Composites

The material(s) used in orthotics determines the function they’ll serve for the wearer.


Leather was the original orthotic material used to make arch supports. The shoemaker would mold it to make a higher medial flange to support the mid-foot and flatter heel cup. It’s still used today as a more comfortable covering for rigid orthotics.


Thermoplastics can be molded to replicate the foot, when heated. After it’s cooled, the molded shape is retained by the material. Thermoplastics offer an array of plastics used for orthotics. They come in different thicknesses, strengths, and colors, and are used in functional foot orthotics.


Polypropylene is a lightweight, high-strength polymer in comparison with other materials — and it’s recyclable. Ultimately, thermoplastics offer a thin, durable and rigid functional orthotic that is thin enough to slip into dress shoes undetected. However, a chip or other damage can lead the orthotic to crack.


Cork is a natural material and creates a thermoformable sheet when blended with rubber binders. The material, then called thermocork, can be adjusted using a sanding wheel. It comes in many different weights and widths. It vacuums well to offer a strong, but tolerant orthotic. Thermocork lite is a cork and ethylene vinyl acetate (EVA) blend.


This polymer is more widely known as high-molecular-weight, high-density polyethylene (HDW-HDPE). It’s a waxy, sturdy, inert, and elastic polymer. This allows for a high melt strength, and the material is then deep drawn without thinning. After the heating and vacuum process, modifications can be made by simply cold forming (hammering). Subortholen is used in functional foot orthotics.


Acrylic is also used in orthotics. For example, Rohadur is a nylon-acrylic copolymer made up of methyl methacrylate, and acrylonitrile. This acrylic is heat-moldable and available in varying thicknesses. It’s used in orthotics where more functional control is desired.

Composite carbon fibers

Composite carbon fibers are made by combining acrylic with carbon fibers. This combination creates stiff sheets of material that is suitable for thin functional orthotics. The composite material is more challenging to manipulate because of its higher softening temperature; faster vacuuming and absolute accuracy when molding. Modifications are difficult on the finished product.

Polyethylene Foams

There is a wide-range of materials in the polyethylene foam category. They go by various trade names such as Aliplast®, Dermaplast® and Plastazote®. They are all cross-linked polyethylenes (CL-PE) creating closed-cell foams. These materials are perfect for full contact, shock and pressure reducing accommodating orthotics.

These materials are synthetic and widely used in accommodative orthotics

EVAs are open-cell, which allows for breathability and cushioning, while closed-cell provides cushioning. Polyurethane foam is used because of its light-weight and cushioning support. Neoprene in orthotics is used for shock absorption, impact reduction and general comfort. Silicone gel composed of polyurethane gel is used to relieve pain, absorb shock, and provide overall cushioning.

Off the Beaten Footpath

Sols is a company that takes a 10-second video of your foot and translates that into a custom, 3D-printed foot orthotic using NASA grade nylon with an antimicrobial coating.

If you want to reduce your carbon footprint, Ortholite® offers a polyurethane insole that is made from almost 50% bio-oil, using castor oil. This insert conforms to your foot over time, creating an insert customized by you.

There are a variety of materials used in orthotics offering everything from corrective help, to shock absorption, to just plain comfort. With a little bit of research and a conversation with your doctor, you should be able to find the foot orthotic that’s right for you.

Image by stanga/123RF Stock Photo.
Source: “Overpronation,” Sports Injury Clinic.
Source: “Supination,” Sports Injury Clinic.
Source: “Material Choices for Foot Orthotic Design,” by Seamus Kennedy,, February, 2008.
Source: “Orthotic Materials,” by Cox Orthotics,
Products Source: “ViscoPed,” Bauerfeind,
Source: “Technology,” Sols,
Source: “Sustainabilty, Ortholite,