A CPG twist on a holiday classic, with happier results
Total ion chromatogram of 4 chocolate samples showing peaks of caffeine and theobromine in water extraction.
Total ion chromatogram of 4 chocolate samples showing peaks of caffeine and theobromine in water extraction.
ISO and ASTM are drafting a new standard on qualification of polymeric materials used for additive manufacturing using powder bed fusion (ISO/ASTM DIS 52925:2020). This standard is focused on polyamide 12 and 11, but the standard may be applicable to other polymeric materials.
The standard discusses the following test methods:
These tests are all performed by Cambridge Polymer Group, and can be used to qualify new material or requalify used material. Contact us for more information.
The ASTM workshop on Reprocessing Personal Protective Equipment (September 9-10, 2020, virtual workshop) is looking for presentations on the following topics:
To participate in the workshop, your 300-word abstract is due no later than July 26, 2020. Please see the ASTM symposium page for submission instructions.
Australian thorny devil (left); scanning electron micrographs of the micro-channels found on the lizard's skin (right). .
The Australian thorny devil (meloch horridus) is a desert-going lizard that has developed an impressive application of transport phenomenon to make the most of a limited source of water in the arid regions it inhabits. The lizard has a skin surface that contains a continuous series of micro-channels that are capable of transporting water by capillary action towards the lizard’s mouth. As the lizard crawls over and under vegetation that contains droplets of dew, it effectively collects this water all over its body, allowing it to drink on the run. The lizard’s mouth, suitable for eating ants, is not adapted to drink water directly, necessitating this curious mode of drinking.
Capillary transport is quite common in nature. It is the mechanism by which water is moved from the roots of trees up to its leaves. It is the means that our eyes drain tear fluid through the narrow tear ducts in our eyelids. This ability results from the attractive nature that water molecules have for each other, termed the forces of cohesion. This cohesion leads to surface tension, or the resistance of the surface of a liquid to an external force, such as a solid object penetrating the liquid. This tensile force causes the liquid to form a meniscus when placed in a narrow capillary, and if sufficient adhesion occurs between the water and the capillary wall, the water will be pulled along in the capillary, even overcoming the force of gravity if the capillary diameter is sufficiently small.
While this mode of drinking may appear convenient, one could argue that the quaffable benefits of the thorny devil's capillary-driven drinking mechanical are outstripped by the social liability of its crenulated dermis. But from a surface science point of view, the thorny devil has arrived at a low energy, high efficiency method of harvesting water.
For more information on surface energy measurements, contact Cambridge Polymer Group or visit our website.
CPG is now fully open and able to work on ALL projects; we are no longer limited to COVID-19 response or projects essential for medical emergency staff. Turnaround times may still be affected due to the need to social distance.
Cambridge Polymer Group is in compliance with Massachusetts Governor Baker's May 18th re-opening schedule. CPG has been deemed an essential business, and has implemented all safety precautions stipulated by the re-opening order, as well as additional safety measures.
Cambridge Polymer Group is committed to providing a safe environment for our employees and visitors. For the protection of all, we’ve implemented the following requirements:
In addition to these requirements, Cambridge Polymer Group has increased the frequency of cleaning and disinfection of the workplace. These policies and procedures have been implemented to reduce transmission risks and protect our workforce. Your cooperation is appreciated.
If you are dropping off samples and do not need to enter our office or lab space, follow these steps:
Cambridge Polymer Group
CPG employees are making masks for friends, family, neighbors, hospital workers, and the Boston Mask Initiative. Because most stores are closed due to COVID-19, CPG mask makers put their material selection skills to good use while scavenging household supplies. We pooled our mask-making and mask-wearing experiences into the following suggestions:
Better fitting masks are both more effective at preventing coronavirus transmission and less likely to fog glasses, so look for a pattern/design with less opening in the top and sides. Gaps can decrease a mask's effectiveness by over 60%. Your mask should start at the bridge of your nose and end underneath your chin. If your mask does not fit properly, do not keep wearing it.
The CDC recommends that masks should be made of at least two layers. One of our scientists suggests pellon as an inner layer, but acknowledges that it is hard to find in stock. She says any material made of non-woven polypropylene will work as an inner filter (such as bags from running shoe stores).
Filtration efficiency of a cloth mask comprised of high thread count cotton (left/green) and one layer of flannel or two layers of silk or two layers of chiffon (right/blue). Credit: ACS Nano
A recent University of Chicago study found that a hybrid of mask materials provided significant protection from aerosol particles. For the outside of the mask, the study recommends using one layer of tightly woven cotton as a mechanical filter. For the inside of the mask, either flannel (one layer), or silk (two layers), or chiffon (two layers) functions as an electrostatic filter, though not quite as effectively as an N95. For an explanation of how electrostatic filters work, see our N95 app note.
Where to find tightly woven cotton around your house? Look for 400-600 count cotton pillow cases or sheets, quilting cotton, or cotton dish towels.
Unless you know a fashionista willing to let you cut up expensive clothing, it's unlikely you have access to spare silk and chiffon for the inner section of your mask. Flannel is more commonly available; bed sheets or pajamas are two sources you may already have. The downside of flannel is that it tends to be warm - it might be worth ordering some chiffon for summer masks.
Elastic has been sold out from very early in the pandemic. Our mask-making scientists got creative, using hair band elastics, elastic beading cord, bungee cords (the type used for swim goggles), and pieces of straps from old swim suits.
Other mask makers used fabric ties instead of elastic loops. Some of our staff found that masks with ties are more comfortable on the ears and easier to adjust than masks with elastic loops.
Those who prefer elastic but dislike sore ears sewed buttons onto surgical caps or headbands, or used 3D printed straps. The elastic is wrapped around the button or the 3D printed guard instead of the ear.
A metal nose clip shapes the mask to your facial contours and reduces lens fogging. Possible sources of metal include: hair barrettes, disposable foil baking pans, pipe cleaners, paper clips, and plastic coated metal twist ties (such as the kinds used for bread or for vine training). If your mask contains metal, DO NOT MICROWAVE to disinfect. Instead, hand or machine-wash your mask or leave it in direct sunlight.
Some CPG staff decided to pad the nose section of the mask with foam, both for improved seal and comfort over the course of a lab shift. Where to find foam around your house? One possible source is shipping wrap from all of those packages you've been ordering. If you have any broken headphones lying around (don't worry, we won't tell Marie Kondo), they may contain memory foam. Insoles from old sneakers are another potential source of memory foam, but may be too smelly to use.
To further enhance your mask's seal and boost its effectiveness, a recent Northeastern University study recommends wearing a nylon stocking layer over a cloth mask. The study suggests cutting 8-10 inches off the leg of a Q size stocking.
Disclaimer: the Northeastern study was released prior to peer review. However, it was inspired by previous research which found a layer of hosiery over a homemade mask was effective at filtering fallout particles from the 1979 Three Mile Island nuclear disaster.
Some CPG staff decided the stocking layer was too tight and difficult to breathe through (though perhaps we just have larger-than-average heads). In one case, the intense seal around the mouth led to the wetting of both layers of mask cotton with breath moisture. It is essential that your mask remain dry, since natural fibers can swell when wet, impacting mask performance. In our extremely casual observation, wearing the nylon layer did not seem to prevent glasses fogging, despite the improved seal.
Use surgical or sports tape to seal the top of your mask to your face to reduce fogging. DO NOT USE packing or duct tape which can cause skin abrasions. Surgical and sports tape adhesive is designed to allow transmission of air and moisture through the adhesive system, which minimizes skin irritation.
Positioning your glasses/lab goggles on top of the mask can also decrease fogging. Adding either 1) a metal nose clip or 2) padding to the bridge of the nose or 3) bias tape to the top of the mask can help to create a perch for your glasses or goggles to rest on. Most CPG employees found wearing glasses or goggles on top of the mask (with or without a perch) to be the most effective method of reducing or eliminating lens fog.
After taking your mask off, clean your glasses before putting them back on your face since they were just touching the contaminated part of your mask.
Cambridge Polymer Group owns two 3D printers, a PRUSA and a Leapfrog Xeed. We use them for making prototypes and creating custom instrument parts. When Massachusetts Governor Baker issued the shelter-in-place order on March 23rd, we brought our printers home, so that we could join the worldwide movement to alleviate the shortage of personal protective equipment caused by the coronavirus pandemic. The PRUSA called shotgun, so the Leapfrog Xeed had to ride in the backseat.
In the weeks that followed, CPG employees continued to work remotely, and some of us returned to the lab to work on COVID-19 related projects. During down time, our CPG 3D printer operators set to work producing PPE, including CPAP brackets, face shields and ear guards.
Cambridge Polymer printed brackets for CPAP units shipped to Italy in anticipation of infants suffering from COVID-19.
CPG also printed face shields for Massachusetts healthcare workers.
While working in the lab on COVID-19 related projects, CPG scientists discovered firsthand that elastic mask loops cause ear friction. Our CPG 3D printer operators came to the rescue with ear savers. Invented by a 12-year-old Canadian Scout, the 3D printed guard pulls the elastic away from the ears, preventing the elastic from rubbing the ears raw and improving mask fit.
"Virtually nothing comes out right the first time. Failures, repeated failures, are finger posts on the road to achievement. One fails forward toward success." - Charles F. Kettering