Conductive Cellulose-Based Fibers For Clothing: Coming Soon?

Summary of the process of producing side-by-side PANI and cotton cellulose fibers. (Credit: Wongcheng Liu et al., 2023)
Summary of the process of producing side-by-side PANI and cotton cellulose fibers. (Credit: Wongcheng Liu et al., 2023)

With the rise of ‘smart’ devices, it seems like only a matter of time before smart fabrics become an every day thing. Yet a complication with these is that merely threading copper wires into clothing is neither practical nor very durable, which is why researchers have been trying to find a way to combine cellulose-based fibers like cotton with another, conductive material like carbon to create an affordable, resilient material which can provide the pathways for these smart fabrics. Recently a team at Washington State University created a version that integrates polyaniline (PANI, press release for paywalled paper), which is a well-known conductive polymer.

A recent review article by Duan-Chao Wang and colleagues in Polymers covers the research in conductive fibers, with conductive additives ranging from carbon nanotubes (CNT) and graphene to various metallic compounds and conductive polymers. As noted by Wang et al., a major aspect to successful commercialization is enabling scaling and cost-effectiveness of producing such fibers. This is the core of the achievement by the WSU team, who used a side-by-side structure of a cellulose substrate and the PANI conductive covering, which should be easier to produce and more durable than previous attempts to merge these two materials into conductive fibers suitable for fabrics.

Other research by Zhang-Chi Ling and colleagues, as reported earlier this year in NPG Asia Materials, details the creation of composite, conductive fibers made from bacterial cellulose with in-situ entanglement of CNTs. With even 100,000 bending cycles not showing much degradation, this could be another good candidate for conductive fabrics. Which of these approaches will first hit mass-production is still anyone’s guess, but we might see them sooner rather than later.

E-Dermis: Feeling At Your (Prosthetic) Fingertips

When we lose a limb, the brain is really none the wiser. It continues to send signals out, but since they no longer have a destination, the person is stuck with one-way communication and a phantom-limb feeling. The fact that the brain carries on has always been promising as far as prostheses are concerned, because it means the electrical signals could potentially be used to control new limbs and digits the natural way.

A diagram of the e-dermis via Science Robotics.

It’s also good news for adding a sense of touch to upper-limb prostheses. Researchers at Johns Hopkins university have spent the last year testing out their concept of an e-dermis—a multi-layer approach to expanding the utility of artificial limbs that can detect the curvature and sharpness of objects.

Like real skin, the e-dermis has an outer, epidermal layer and an inner, dermal layer. Both layers use conductive and piezoresistive textiles to transmit information about tangible objects back to the peripheral nerves in the limb. E-dermis does this non-invasively through the skin using transcutaneous electrical nerve stimulation, better known as TENS. Here’s a link to the full article published in Science Robotics.

First, the researchers made a neuromorphic model of all the nerves and receptors that relay signals to the nervous system. To test the e-dermis, they used 3-D printed objects designed to be grasped between thumb and forefinger, and monitored the subject’s brain activity via EEG.

For now, the e-dermis is confined to the fingertips. Ideally, it would cover the entire prosthesis and be able to detect temperature as well as curvature. Stay tuned, because it’s next on their list.

Speaking of tunes, here’s a prosthetic arm that uses a neural network to achieve individual finger control and allows its owner to play the piano again.

Thanks for the tip, [Qes].

Is That Google In Your Pants?

Google’s Project Jacquard is tackling the age old gap between controlling your electronic device and touching yourself. They are doing this by weaving conductive thread into clothing in the form of a touch pad. In partnership with Levi Strauss & Co., Google has been designing and producing touch interfaces that are meant to be used by developers however they see fit.

touch-sensitive-jeans-thumbThe approach that Project Jacquard has taken from a hardware standpoint is on point. Rather than having an end user product in mind and design completely towards that goal, the project is focused on the interface as its product. This has the added benefit of endless varieties of textile interface possibilities. As stated in the video embedded after the break, the conductive touch interface can be designed as a visibly noticeable difference in material or seamlessly woven into a garment.

As awesome as this new interface may seem there are some things to consider:

  • Can an unintentional brush with another person “sleeve dial” your boss or mother-in-law?
  • What are the implications of Google putting sensors in your jeans?
  • At what point is haptic feedback inappropriate? and do we have to pay extra for that?

We’ve covered e-textiles before from a conductive thread and thru hole components approach to electro-mechanical implementations.

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Poking Around Textiles With Your Multimeter

Looking for a fun wearable electronics project? While you can buy specific fabric and conductive thread for your projects, sometimes you can even find conductive fabric where you might not expect it!

In this latest video by Adafruit, [Becky Stern] goes undercover at a fabrics store with her trusty multimeter to find some new material that can be used for electronics projects! While pickings are slim, she made some useful discoveries — most metallic fabrics aren’t conductive, but some are — You’ll definitely need to take your multimeter with you.

Another funny quirk is that some fabrics are only conductive in one direction! Which could make for a really cool project that seemingly defies conventional wiring — or you can sew a conductive thread perpendicular to the continuity to connect it all together.

Continue reading “Poking Around Textiles With Your Multimeter”