Polymer Adds Flexibility to Neural Probe

Flexible polymer neural probes.

Polymer fibers designed to mimic fibrous geometry of the nerves allow for simultaneous optical stimulation and neural recording in the spinal cord. The picture illustrates the flexibility of the bifunctional neural probes and their ability to accommodate deformation due to the movement of vertebrae.

Parkinson’s disease, spinal cord injury, and chronic pain are devastating neurological conditions that are difficult for physicians to treat. The trouble lies in the inability of the physician to bypass or heal damaged neurons. A device capable of stimulating neural tissue and recording the subsequent activity simultaneously could potentially help repair damaged neural tissue in patients with paralysis due to spinal cord injury. A device of this nature would have to be highly flexible and biocompatible.

New Approach to Implants

Graduate student Chi (Alice) Lu, of the Polymer Science and Technology Program at MIT is the designer of highly flexible neural probes. The probes are made using a polycarbonate (PC) and cyclic olefin copolymer (COC) core. The PC fiber is approximately 1.5 inches thick and is pulled using thermal drawing, until it reaches a thickness of 400-1,100 microns (µm). The fiber is then etched to reach a final thickness of 180-230 µm. The flexibility of the electrodes is extremely high, and they can be tied into a knot. Tests showed the probes performed well under the stressful environment and natural movements of the body. The design also includes a waveguide for stimulating optically and conductive polyethylene (CPE) electrodes to record data.

The experimental procedure included testing the neural implant in mice whose neurons responded to blue light. The mice expressed the protein channelrhodopsin 2 (ChR2), which is light-sensitive and caused the neural response. A neuronal response is generated by shining a light on the spinal cord; the response is recorded. Lu said:

The next step will be a chronic study. I think the challenge will be how to implant even a very flexible device without paralyzing the animal. We are just interfacing something harder than the tissue with the body. And then when the animal moves, the device has to follow this movement organically otherwise it will potentially paralyze the animal. So this will be another challenge, how to find a good spot for stimulation and recording, but not damage the tissue.

Existing Implantable Devices

Currently, deep brain and spinal cord stimulation uses antiquated electrode technology. The implants are not biocompatible, and their inflexibility causes mechanical damage to the surrounding tissue. The materials used for the implants elicit an adverse response from the neurological tissue, which often leads to the encapsulation of the implant in scar tissue, which can render the implant useless.

Another potential problem is the deposition of the electrode material into the neural tissue, which is caused when an electrical current passes through the probe, etching off material. However, due to advances in materials science and fabrication techniques, new and better neurological implants are making the news.

Probe Potential

There are limitations as far as medical applications are concerned. Human neurons are not light-sensitive, with the exception of optical neurons. Polina Anikeeva, AMAX assistant professor in materials science and engineering at MIT, would like to see this work taken a step further, aiding in the development of flexible biomimetic optoelectronic neuroprosthetics. This would allow the device to communicate with nerves for use with limb prosthetic devices.

Lu’s neural device may not be ready for human trials, but it is a step in the right direction. Biocompatibility is critical for an implantable neural device to function properly, if at all. Flexibility is also vital in an area as sensitive and dynamic as the central nervous system. Chronic studies will give us a better idea of how well these novel neural devices will work in the brain and spinal cord.

Image by Chi (Alice) Lu and Polina Anikeeva.
Source: “Flexible Polymer Probes and Magnetic Nanoparticles Promise Breakthroughs for Treating Paralysis, Brain Disease,” by Denis Paiste, www.phys.org, September 3, 2014.
Source: “Magnetic Nanoparticles and Polymer Fiber Probes for Treating Neurological Disorders,” by Alessandro Pirolini, www.azom.com, September 4, 2014.
Source: “Stimulating Nerves With Light,” by Denis Paiste, mpc-www.mit.edu, August 31, 2014.
Source: “Flexible Probes for Spinal Cord Integration,” Materials Views, www.materialsviews.com, September 5, 2014.
Source: “Biocompatible Materials for Optoelectronic Neural Probes: Challenges and Opportunities,” by Polina Ankeeva, National Academy of Engineering, www.nae.edu, Winter 2013.
Source: “Polymer Fiber Probes Enable Optical Control of Spinal Cord and Muscle Function In Vivo,” by Chi Lu, et al., Advanced Functional Materials, August 26, 2014, DOI: 10.1002/adfm.201401266.

Micro Pumps Hold Promise for Diagnosing Diseases

Acoustofluidic pump for lab-on-a-chip.

An acoustically powered pumping device with 250 micron long oscillating structures driven by a piezoelectric transducer mounted on a glass slide.

Imagine a world where tiny pumps could be used to determine whether or not someone is carrying a disease. The results would be available in minutes instead of a few days or more — the whole procedure could take place in the duration of a doctor’s appointment. Welcome to the future where a lab-on-a-chip device can give you the information you need when you want it — now.

Penn State researchers led by Tony Huang, professor of engineering science and mechanics in Penn State’s College of Engineering, have developed an acoustofluidic pump with polydimethylsiloxane (PDMS) microfluidic channels that uses a piezoelectric transducer – roughly the size of a quarter — to power it. Huang said:

The field of microfluidics and lab-on-a-chip technologies has the potential to revolutionize the healthcare industry with cost-effective, high-performance miniature biomedical diagnostic devices. Despite its tremendous potential, the field has only delivered very limited numbers of products and tools for real-world applications. One of the reasons is that it is difficult to fabricate micropumps that are simple and inexpensive, yet reliable and effective.

Low-Cost Devices

The research group used an effective design for the microfluidic device to prove that low powered acoustic waves could transport fluids with accuracy and consistency. The total cost to construct the device is $20-30, with the disposable chip itself costing just 10 cents. The cost is somewhat higher than paper diagnostic counterparts such as pregnancy tests, but is much more accurate and flexible. Therefore, it can reliably provide assessment measurements for diseases including — but not limited to — HIV, cancer, infectious diseases, and cardiovascular disease.

Today’s diagnostic technology is expensive. In the U.S., it can cost as much as $800 for a diagnostic test. The price includes the cost of the equipment used and highly trained lab technicians to gather and interpret the results. This disposable-chip technology holds the promise of one day bringing down the cost of health care with a device that is inexpensive, user-friendly, and at the same time, dependably accurate. Future battery-powered versions of the device could bring low-cost, precise, disease diagnosis to regions where electricity is not available.

How It Works

The microfluidic pump design was created by bonding a PDMS channel onto a glass slide and attaching a piezoelectric transducer to it. The PDMS channel is rectangular, creating four channels (upper, lower, right, and left) and allowing for recirculation in a counter-clockwise manner. The lower channel is the pumping channel, with an oscillating sequence of structures built into its sidewalls. The small piezoelectric transducer creates the oscillations. Huang said:

Our pump is quite unique. It’s reliable and programmable, with a minimum of hardware, yet highly precise. The flow rates can be tuned across a wide range, from nanoliters per minute to microliters per minute. I don’t see anything out there with our characteristics.

A device like this could significantly reduce the high-cost of health care and the need of lengthy waits for vital, life-changing results. Furthermore, it can offer quick, accurate and consistent results to people around the world who don’t have access to electricity let alone doctors and diagnostic tests. Not only might this device revolutionize the health-care industry, it has the potential to impact the health of people around the world.

Image: Po-Hsun Huang and Tony Jun Huang, Penn State.
Video by Penn State University MRI, youtube.com.
Source: “A Reliable and Programmable Acoustofluidic Pump Powered by Oscillating Sharp-Edge Structures,” by Tony Huang, et al., Lab on a Chip, September 04, 2014, DOI: 10.1039/C4LC00806E.
Source: “Cost-Effective, High-Performance Micropumps for Lab-on-a-Chip Disease Diagnosis,” Materials Research Institute Penn State, www.mri.psu.edu, September 4, 2014.
Source: “Microfluidics and Lab-on-a-Chip Technologies Help Develop Piezoelectric Transducer-Powered Acoustofluidic Pump,” Azonano.com, www.azonano.com, September 5, 2014.
Source: “Cost-Effective, High-Performance Micropumps for Lab-on-a-Chip Disease Diagnosis,” Newswise, www.newswise.com, September 4, 2014.

California Poised to Ban Single-Use Plastic Shopping Bags

plastic.bag.litterCalifornia may soon become the first state to ban single-use plastic grocery bags. On August 29, the state’s senate passed a bill that if enacted would be the first law of its kind in the country. During a gubernatorial debate on September 4, California’s Gov. Jerry Brown announced he would sign the bill, which he has until the end of September to do. He said:

I probably will sign it, yes. In fact, I’ll tell you why I’m going to sign it: there are about 50 cities with their own plastic bag ban, and that’s causing a lot of confusion. This is a compromise; it’s taking into account the needs of the environment and the needs of the economy and the needs of the grocers.

Gov. Brown was referring to bans in individual cities throughout California, including major cities like Los Angeles and San Francisco. When the statewide ban passed the Senate, a total of 124 bans on single-use PE bags were in place.

After plastic bag manufacturers spoke out against the proposed ban, claiming it would cause a loss in jobs, the bill was amended to include $2 million in assistance to local plastic bag makers so they can change their production lines to create more heavy-duty, multi-use bags to be sold at checkout lines for 10 cents.

Environmental Impact

Shopping bags made of polyethylene (PE) are used by grocery stores all over the U.S. Thirteen billion bags are handed out to California shoppers each year. The bags are often not recycled and end up drifting in the environment like tumbleweeds or clogging up waterways.

Cleaning up plastic bag waste in California costs $34 to $107 million each year. Environmental groups such as Californians Against Waste and Heal the Bay have been pushing this legislation to help cut down on landfill waste and environmental pollution. Marine life is at risk when the bags pollute the water. Sea turtles are especially prone to harm because plastic bags are easily confused for jellyfish, one of the animal’s primary sources of food. Mistakenly eating a plastic bag can lead to death.

The ban would begin on July 1, 2015, for large grocery stores and pharmacies. On July 1, 2016, the ban will be enforced for convenience store, liquor stores, and small markets. Plastic bags used for produce, meats, and bulk foods will still be available for customers. Restaurant bags will still be allowed, as well as bags at hardware stores and certain retail stores.

Opposition to Bill

The topic is hotly debated by people who believe the ban is a government intrusion into small business. Another controversial issue is charging 10 cents for bags that previously were offered for free, taking an unnecessary toll on the poor and working class and creating a windfall for grocers. Plastic bag manufacturers argue the $2 million dollars earmarked for retooling their factories is just small portion of the total cost they will have to pay out for such a task. The manufacturers also believe that job loss is inevitable.

While there are understandable and justifiable arguments on both sides of the legislature, the fact remains that single-use bags are a major source of pollution in California. Recycling initiatives have had no impact. Save the Bay literature reported the removal of more than 1.3 million plastic bags from coastal regions around the world in one day last year.

We may not all agree on the banning of single-use plastic bags, we can all agree there is a growing problem with the pollution of these convenient carriers, and something needs to be done about it.

Image by grahamc99.
Video by HealtheBay, YouTube.com.
Source: “California Legislature Bans The Bag!Heal the Bay, www.healthebay.org.
Source: “California on Track to Enact Nation’s First Statewide Plastic Bag Ban,” by Katie Sola, www.mashable.com, September 6, 2014.
Source: “California to Be First U.S. State to Ban Plastic Bags,” Yahoo News, www.news.yahoo.com, September 5, 2014.
Source: “California Plastic Bag Ban Would Be First of Its Kind in the Nation,” by Aaron Mendelson, www.huffingtonpost.com, August 30, 2014.
Source: “California Poised for 1st State Bag Ban,” by Deborah Sullivan Brennan, www.utsandiego.com, September 5, 2014.
Source: “Myths vs. Facts Regarding Single Use Bag Bans and Fees,” Heal the Bay, www.savesfbay.org.
Source: “Sea Turtle Diet,” www.seeturtles.org.

The Inventors of Modern Plastics

Billiard balls made of Bakelite, an early form of plastic.

It’s hard to imagine a world without plastic, but these polymers, now ubiquitous, are in fact a fairly recent invention.

Here’s a look at some of the inventors of modern plastic. Each of these men influenced the next with his determination and critical inventions. They learned from the shortcomings of their predecessors’ innovations, and built on their ideas until finally the product met the expectations they all sought.

Alexander Parkes

Alexander Parkes was born in Birmingham, England, on December 29, 1813. His father made brass locks, and at a young age Parkes became his apprentice. He went on to work in metal foundries, becoming a metallurgist. His work there allowed him to understand and employ the art of electroplating — applying thin layers of metal to different items for decoration. His skill was unsurpassed, and he developed new techniques that allowed him to coat items as delicate as a spider web.

Parkes interest turned to the properties of rubber. He wanted to create a synthetic material that could be molded while hot. His first patent was issued in 1841 for his method of creating waterproof fabric with thin coats of rubber. He continued working with rubber and was awarded many more patents for processes that used the material for techniques combining electroplating and rubberizing, as well as for recycling rubber.

Parkes created the first fully synthesized plastic in 1885. He dissolved cellulose nitrate in alcohol, and camphor containing ether. The result was a product that could be easily molded when heated yet retained its shape and firmness when cold.

He called his invention Parkesine, and started the Parkesine Company in 1866. Unfortunately, it did not last. He could not produce the material inexpensively and on a large scale. On top of that, the material was flammable and prone to breaking. He sold the company to his partner, who created a few different plastics after that, but none had staying power.

Alexander Parkes lived to be 76 years old. He was married twice and had 17 children and more than 80 patents. He died on June 29, 1890.

John Wesley Hyatt

John Wesley Hyatt was born on November 28, 1837, in Starkey, New York. As a young man, he worked as a printer. At the time, the New York Billiard Ball Company was offering $10,000 to the person who could come up with a new material for making billiard balls that had all the characteristics of the original ivory balls. Ivory was expensive and becoming scarce, as were the elephants.

Hyatt’s interest was piqued. He tried different materials to make the billiard balls. Although he didn’t succeed, he was able to use one of his newly invented materials, which consisted of wood pulp and shellac, to make pressed dominoes and checkers and start a business.

He continued experimenting using Alexander Parkes’ solid cellulose Parkesine and another material, inventor Frederick Scott Archer’s liquid nitrocellulose. Using these two materials, Hyatt discovered a new substance he named Celluloid. The materials used for making Celluloid were nitrocellulose, which comes from wood or cotton and is flammable, camphor, a waxlike resin from Asian camphor trees, and alcohol. Hyatt created the new material by pressing the three materials together in a mold while heating them.

Celluloid was used for many products, but most notably among them were billiard balls, false teeth, and piano keys. Use of the product was limited due to its high flammability from the nitric acid used to make the nitrocellulose.

Celluloid film was used in filmmaking for more than 120 years. Due to the expensive and difficult production of celluloid film, the industry began replacing it in the 1950s with a similar version using acetic acid instead of nitric acid. The films made using celluloid are fragile and flammable so they are kept under strict conditions. Today the material is used for pingpong balls and guitar picks.

John Wesley Hyatt passed away on May 10, 1920 with more than 200 patents to his name.

Leo Hendrik Baekeland

Leo Hendrik Baekeland was born in Ghent, Belgium, on November 14, 1863. He excelled in chemistry and physics at the University of Ghent. Hyatt’s celluloid influenced Baekeland. He invented a photographic paper he called Velox, which permitted the development of photographs using artificial light. The development of photographs before Velox had to be done under sunlight. George Eastman of Eastman Kodak bought the technique from Baekeland for $750,000 in 1899.

Baekeland continued working and invented the first thermoset plastic, which he named Bakelite. The resin was extremely malleable and could be permanently set under high pressure. The material, which was made of carbolic acid and formaldehyde, was easily reproducible, inexpensive, and not flammable.

After receiving a patent in 1909, Baekeland presented Bakelite to the world. The products made using the novel material included radios, costume jewelry, appliances, and much more. When his patents ran out, competitors were quick to market similar products.

Leo Hendrik Baekeland died at the age of 80 on February 23, 1944.

Image by Gregory Tobias, from the collection of the Chemical Heritage Foundation.
Source: “The Men Who Invented Plastic,” Connecticut Plastics, www.connecticutplastics.com.
Source: “Alexander Parkes Biography,” History of Plastic, www.historyofplastic.com.
Source: “Alexander Parkes — Materials Man and Polymath,” by Sue Mossman, www.sciencemuseum.org.uk.
Source: “John Wesley Hyatt (1837-1920),” Plastics Historical Society, http://www.plastiquarian.com/.
Source: “John Wesley Hyatt,” by the editors of The Encyclopædia Britannica, www.britannica.com.
Source: “Leo Hendrik Baekeland,” by the editors of The Encyclopædia Britannica, www.britannica.com.
Source: “Leo Hendrik Baekeland,” www.pbs.org.