Tikalon Header Blog Logo

Transistor Threads

October 7, 2019

One downside of being human is mortality, and people have always wondered why some people die young, while others live a long life. The ancient Greeks imagined that such destiny was wrought by a trio of beings who were the instantiation of destiny. These were called the Moirai (Μοιραι, Fates in English). There was Clotho (Κλωθω), who who spun a thread of life, Lachesis (Λαχεσις), who measured out a length, and Atropos (,Ατροπος), who cut the allotted length.

The Three Fates, Clotho, Lachesis, and Atropos

The Three Fates (Moirai), Clotho, Lachesis, and Atropos.

(Wikimedia Commons photograph by Andreas Praefcke of a sculpture by Johann Gottfried Schadow (1764-1850).)

(Click for larger image.)

A thread is an important part of another story in Greek mythology, that of Ariadne, Theseus, and the Minotaur. The Minotaur was creature with the head of a bull and the body of a man that lived at the center of a maze-like structure called the Labyrinth. According to the story, Theseus was among a group of young men and women being sacrificed to the Minotaur.

Ariadne gave Theseus a sword to kill the Minotaur, and also a ball of thread to allow him to find his way out of the labyrinth once this had been done. Ariadne's thread is now the name of a method of exhaustive search in which you test each path at a logical juncture, and back-track to the last last state when the trial leads to a dead end. Either a solution is reached, or all possible paths have been tested to ensure that there is no solution.

Labyrinth etching by Toni Pecoraro (2007)

A depiction of the Labyrinth.

While it is clear from the myth that this maze was a complex branching maze with dead-ends, most classical depictions showed the Labyrinth as being unicursal; that is, just a long single corridor.

(A 2007 Wikimedia Commons image by Toni Pecoraro.)

A thread is an important part of another story from antiquity, that of the Sword of Damocles. In this story, Damocles is envious of the lifestyle of King Dionysius, so Dionysius offers to make him king for a day. When Damocles is seated at the king's throne, he is surprised to see that Dionysius had a sword suspended above the throne by a single hair of a horse's tail. The lesson was that being king has its dark side, also, since there is always the fear of internal and external enemies. From this story comes the adage, to hang by a thread, which is included in the 16th century book of famous adages, Adagia, by the Dutch scholar, Erasmus (1466-1536).

Threads were a very important stage in the development of the incandescent light bulb. Joseph Swan (1828-1914), an English physicist, chemist, and inventor, was one of the first to develop a successful incandescent light bulb, demonstrating ever improved versions from 1875 onward. All of these used carbon filaments in a vacuum glass bulb, some of the better filaments created by carbonizing cotton thread. He commercialized his invention by lighting homes and the Savoy Theatre, London. Thomas Edison similarly tested carbonized thread in his early light bulbs.[1]

English physicist, chemist, and inventor, Joseph Wilson Swan (1828-1914), and a plaque marking his electrified house

English physicist, chemist, and inventor, Joseph Swan (1828-1914), and a commemorative plaque marking his electrically-lighted house. Since Swan and Edison both had strong patent positions in Great Britain, their companies merged there in 1883 to create the Edison & Swan United Electric Light Company. (Left, Joseph Swan from Wikimedia Commons. Right, a Wikimedia Commons image by HJ Grey. Click for larger image.)

A team of engineers from Tufts University (Medford, Massachusetts) has recently developed a transistor made from linen thread.[2-3] This field-effect transistor is enabled by an ionic gate, and the allure of such a transistor is that it might be woven into fabric or more easily implanted surgically for diagnostic monitoring since they are extremely thin, soft and flexible.[3] Compared with flexible electronics based on polymers and other materials, these thread-based electronics have superior flexibility,and they can be manufactured without the need for a cleanroom.[2-3] I wrote about ion-gated transistors in a recent article (Ion-Gated Transistors, July 1, 2019). As the authors write in their abstract in ACS Applied Materials and Interfaces,
"...Real-time monitoring of human biomarkers is becoming increasingly important to modern medicine and patient wellness. Such monitoring is possible due to advances in soft and flexible materials, devices and bioelectronics systems. Compared to other flexible platforms, multifilament textile fibers or threads offer superior flexibility, material diversity, and simple ambient processing to realize a wide range of flexible devices such as sensors, electronics, and microfluidics."[2]

Dimensions of the thread based transistor.

Dimensions of the thread based field-effect transistor.

(Portion of an image from the Tufts University Nano Lab, also available here.)

The thread acts as a substrate for a carbon nanotube semiconducting network formed between the source and drain electrodes. The ionic gate is a colloidally dispersed gel of silica nanoparticles, and the ionic liquids, 1-ethyl-3-methylimidazolium, and bis(trifluoromethylsulfonyl)imide (EMI-TFSI).[2] The manufacturing process involves coating a linen thread with carbon nanotubes, attaching two thin gold wires for the source and drain connections, and surrounding the thread with the electrolyte gel, called an ionogel, that's connected to the gate electrode.[3] Unlike the gate material in conventional transistors, the ionogel can stretch and flex along with the thread.[3]

Top and cross-sectional views of the thread based transistor.

Top and cross-sectional views of the thread-based field-effect transistor. The source (S) and drain (D) connections are to the carbon nanotube coating on the thread. The gate connection is through an electrolytic gel, and a gate voltage above a threshold will cause a flow of electrons through the transistor. The gel electrolytes are 1-ethyl-3-methylimidazolium (EMI), and bis(trifluoromethylsulfonyl)imide (TFSI) (Reformatted image from the Tufts University Nano Lab, also available here. Click for larger image.)

Not only did the Tufts research team fabricate working thread transistors, they also interconnected them to form functioning logic gates and small-scale integrated circuits.[2] They developed thread-based sensors for temperature, glucose, and strain.[3] They also created microfluidic threads for drawing fluids from surrounding tissues, and for dispensing drugs.[3] They created an integrated circuit multiplexer and connected it to thread-based sensors for detecting sodium and ammonium ions, which are diagnostic of liver and kidney function.[3] Says Rachel Owyeung, a graduate student at the Tufts University School of Engineering and the first author of the study.
"In laboratory experiments, we were able to show how our device could monitor changes in sodium and ammonium concentrations at multiple locations... Theoretically, we could scale up the integrated circuit we made from the TBTs to attach a large array of sensors tracking many biomarkers, at many different locations using one device."[3]

The utility of such thread-based biosensors is summarized by Sameer Sonkusale, a professor of electrical and computer engineering at Tufts University School of Engineering and the corresponding author of the study, "There are many medical applications in which real-time measurement of biomarkers can be important for treating disease and monitoring the health of patients. The ability to fully integrate a soft and pliable diagnostic monitoring device that the patient hardly notices could be quite powerful."[3]

This research was supported by the National Science Foundation.[3]


  1. Thomas Alva Edison, "Electric lamp," U.S. Patent No. 223,898, January 27, 1880.
  2. Rachel E. Owyeung, Trupti Terse-Thakoor, Hojatollah Rezaei Nejad, Matthew J. Panzer, and Sameer R. Sonkusale, "Highly Flexible Transistor Threads for All-Thread Based Integrated Circuits and Multiplexed Diagnostics," ACS Appl. Mater. Interfaces, August 5, 2019, https://doi.org/10.1021/acsami.9b09522.
  3. Mike Silver, "Engineers make transistors and electronic devices entirely from thread," Tufts University Press Release, August 21, 2019.

Linked Keywords: Human; mortality; death; youth; longevity; long life; ancient Greece; ancient Greeks; destiny; instantiation; Moirai; Fates; Clotho; thread (yarn); life expectancy; Lachesis; Atropos; Three Fates; Wikimedia Commons; Andreas Praefcke; Johann Gottfried Schadow (1764-1850); Greek mythology; Ariadne; Theseus; Minotaur; head; bull; body; man; center (geometry); maze; Labyrinth; human sacrifice; sword; animal slaughter; kill; sphere; ball; Ariadne's thread; algorithm; method; brute-force search; exhaustive search; logic; logical; juncture; problem solving; solution; branch (computer science); branching; classics; classical; hall; corridor; Toni Pecoraro; antiquity; Sword of Damocles; Damocles; lifestyle (sociology); Dionysius II of Syracuse; King Dionysius; throne; horsehair; hair of a horse's tail; lesson; monarch; king; enemy; enemies; adage; 16th century; book; Adagia; Dutch people; scholarly method; scholar; Erasmus (1466-1536); incandescent light bulb; Joseph Swan (1828-1914); English; physicist; chemist; invention; inventor; carbon; filament; vacuum; glass; carbonization; carbonize; cotton; commercialization; commercialize; home; Savoy Theatre, London; Thomas Edison; commemorative plaque; electric light; house; patent; Great Britain; company; companies; merger; Edison & Swan United Electric Light Company; >HJ Grey; electrical engineering; engineer; Tufts University (Medford, Massachusetts); transistor; linen; field-effect transistor; ion; ionic; gate; weaving; woven; textile; fabric; implant (medicine); surgical implant; diagnostic; sensor; monitor; deflection (engineering); flexible; electronics; polymer; material; manufacturing; manufacture; cleanroom; abstract; ACS Applied Materials and Interfaces; biomarker (medicine); medicine; patient; health; wellness; bioelectronics; bioelectronics system; room temperature; ambient; microfluidics; Tufts University Nano Lab; substrate; carbon nanotube; semiconductor; semiconducting; electrode; colloid; sispersion (chemistry); disperse; gel; silicon dioxide; silica; nanoparticle; ionic liquid; 1-ethyl-3-methylimidazolium; bis(trifluoromethylsulfonyl)imide; coating; gold; wire; ion gel; ionogel; cross-section; electrolyte; electrolytic; gel; voltage; threshold voltage; electric current; flow of electrons; logic gate; integrated circuit; temperature; glucose; deformation (mechanics); strain; fluid; tissue (biology); harmaceutical drug; multiplexer; sodium; ammonium; ions; diagnosis; liver; kidney; Rachel Owyeung; postgraduate education; graduate student; Tufts University School of Engineering; author; laboratory; experiment; Sameer Sonkusale; professor; electrical and computer engineering; real-time computing; disease; health; National Science Foundation.