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Background
This page is dedicated to the literature review of Open Source wearable electronics made with embroidery machines.
As technology gets more powerful, small, and integrated into our daily lives, there is an increasing demand for adding electronics to our clothing or other cloth. There are lots of potential applications for this technology, and one of the current main focuses is on health monitoring.
The goal in utilizing embroidery machines is to increase wearability and user comfort. The embroidered thread can be used to create the circuits and components, which removes the need for rigid PCBs and other obtrusive parts. The embroidered thread is flexible and integrates seamlessly (pardon the pun) into any fabrics.
Some of the articles in review are not specifically utilizing embroidery machines, or the embroidery plays a lesser role in the project, but these articles still provide useful insights. Some look at uses of conductive fabrics and related fields of study and can give background information as well as provide methodology and ideas for future advancements in embroidery.
MTU Wearable Electronics Factory This link provides files to embroider circuits to wearable devices. There is also a feature to upload a circuit of your own to be converted to an embroidery file. This page was created and is run by the research group of Dr. Sarah Sun at Michigan Technological University. Srschroc is a researcher currently working on this project. This research group is using the Janome MemoryCraft 400e embroidery machine.
Hui Huang, “CLOUD MANUFACTURING BASED EMBROIDERED WEARABLE ELECTRONICS FOR DAILY ECG MONITORING,” Michigan Technological University, Jan. 2019
Abstract
Wearable electronics have been attracting significant attention in various applications such as consumer electronics, healthcare monitoring, localization and navigation and so on. The demand for advanced wearable electronics brings new challenges for
the wearable technologies, which impose the limitations of the development of the current wearable electronics. The next generation of wearable electronics calls for special attention on several major challenges, which features more convenient, more
energy-efficient and more precise sensing.
In this dissertation, in order to tackle these challenges, three solutions are proposed and the application of ECG monitoring is selected as the validation of our solutions. For the convenience of the wearable ECG monitoring, we propose a new design and
manufacturing approach for the embroidered textile circuits to achieve the fully flexible system integrated into cloth, which is called System-on-Cloth (SoCl). A prototype of embroidered ECG sensor is fabricated and tested based on the proposed approach.
The testing results of the embroidered ECG sensor show that the cloud manufacturing platform can be considered as an effective tool for design and manufacturing the textile circuits based wearable electronics. For the energy efficiency of the ECG monitoring
system, a new ECG signal compression method is proposed for the improvement of energy efficiency via reducing the energy consumption of wireless transmission. The simulation results of the ECG compression show that the new ECG compression method is promising to greatly improve the energy efficiency for the ECG monitoring system. For the precise ECG sensing, a new denoising method is developed to enable the high quality ECG sensing for the embroidered ECG sensor. The experimental results for the ECG denoising method present a better performance than the state of the art methods.
Notes:
A detailed background on the state of wearable electronics is given.
The primary goal of this paper is to demonstrate the capabilities of embroidery machines for making wearable devices. It specifically studies an ECG monitor system to verify the novel manufacturing method and work through specific performance improvements for the ECG device.
A background and new specific methods of decreasing power consumption in wearable devices are explained. Specifically to reduce the power needed to compute heart rate from a noisy signal. This study is important to reduce battery size and increase run life.
A cloud manufacturing platform was developed. This cloud platform allows visitors to download tested and confirmed embroidery files for wearable devices. It also features a system for uploading your own circuit schematic to create custom wearable devices.
Mohamadzade, B., Hashmi, R. M., Roy, B. V. B. S., Gharaei, R., Rehman, S. U., & Abbasi, Q. H. (2019). Recent advances in fabrication methods for flexible antennas in wearable devices: State of the art. Sensors, 19(10) doi:http://dx.doi.org/10.3390/s19102312
Abstract
Antennas are a vital component of the wireless body sensor networks devices. A wearable antenna in this system can be used as a communication component or energy harvester. This paper presents a detailed review to recent advances fabrication methods for flexible antennas. Such antennas, for any applications in wireless body sensor networks, have specific considerations such as flexibility, conformability, robustness, and ease of integration, as opposed to conventional antennas. In recent years, intriguing approaches have demonstrated antennas embroidered on fabrics, encapsulated in polymer composites, printed using inkjets on flexible laminates and a 3-D printer and, more interestingly, by injecting liquid metal in microchannels. This article presents an operational perspective of such advanced approaches and beyond, while analyzing the strengths and limitations of each in the microwave as well as millimeter-wave regions. Navigating through recent developments in each area, mechanical and electrical constitutive parameters are reviewed, and finally, some open challenges are presented as well for future research directions.
Notes:
This article illustrates various methods of making antennas for wearable devices. It explains the benefits and drawbacks to each.
Antennas currently have a trade-off between performance and unobtrusiveness. At the high-performance end, antennas can be made with rigid PCB on ceramics or other materials, but these are more bulky and inconvenient to wear. Flexible and small antennas are much less obtrusive but provide less quality.
Research on flexible and small antennas is increasing their performance.
Problems all antennas face include:
Electrical interference from the body.
Motion artifacts.
Effects of stress/strain from mechanical deformation (via body movement).
Protection from humidity changes or perspiration.
One of the 5 main manufacturing methods used to attempt to mitigate these problems is embroidery/fabric based antennas.
There is a useful table giving electrical properties of various conductive threads on page 5.
This article highlights the key issues for embroidery methods:
Deterioration from being washed.
Fraying during the manufacturing process or from extended wear.
L. Alonso-González, S. Ver-Hoeye, M. Fernández-García, C. Vázquez-Antuña and F. Las-Heras Andrés, "On the Development of a Novel Mixed Embroidered-Woven Slot Antenna for Wireless Applications," in IEEE Access, vol. 7, pp. 9476-9489, 2019, doi: 10.1109/ACCESS.2019.2891208.
Abstract:
A novel mixed embroidered-woven coaxial-fed antenna based on a slotted short-circuited textile integrated waveguide has been designed, manufactured, and experimentally validated for its use in wireless applications. The structure of the antenna and the radiating slot can be manufactured using an industrial loom and a laser prototyping machine, respectively, whereas the conductive vias can be manufactured using a commercial embroidery machine, avoiding subsequent treatments or coating. The manufactured antenna presents a centralworking frequency of 5 GHz and a 20% bandwidth. Good agreement between simulations and measurements has been achieved. In addition, the performance of the antenna has been simulated and analyzed under bent conditions around an air-filled cylinder and using a phantom corresponding to a segment of an arm. This prototype demonstrates the possibility of implementing an alltextile antenna, reducing the backward radiation in comparison to the microstrip-based antennas by the use of a substrate-integrated waveguide topology.
Notes:
This article focuses on flexible antennas. It utilizes both a loom for making conductive cloth, as well as an embroidery machine to embroider conductive thread onto the fabric.
Figure 1 and the accompanying text describe how the cloth and embroidered wire enable the desired flow paths of current. The embroidered wire is used to short circuit between two layers of conductive cloth that are separated by a dielectric layer of cloth.
A key advantage to this new antenna design is that it reduces backward radiation. Figure 14 gives a good visual of what that looks like.
A coaxial cable is still needed, so the system is not fully integrated into the cloth.
When the antenna cloth is bent, as it would be if placed on an arm, the performance is reduced by nearly 30%.
Stoppa, Matteo; Chiolerio, Alessandro. 2014. "Wearable Electronics and Smart Textiles: A Critical Review." Sensors 14, no. 7: 11957-11992.
Abstract
Electronic Textiles (e-textiles) are fabrics that feature electronics and interconnections woven into them, presenting physical flexibility and typical size that cannot be achieved with other existing electronic manufacturing techniques. Components and interconnections are intrinsic to the fabric and thus are less visible and not susceptible of becoming tangled or snagged by surrounding objects. E-textiles can also more easily adapt to fast changes in the computational and sensing requirements of any specific application, this one representing a useful feature for power management and context awareness. The vision behind wearable computing foresees future electronic systems to be an integral part of our everyday outfits. Such electronic devices have to meet special requirements concerning wearability. Wearable systems will be characterized by their ability to automatically recognize the activity and the behavioral status of their own user as well as of the situation around her/him, and to use this information to adjust the systems‘ configuration and functionality. This review focuses on recent advances in the field of Smart Textiles and pays particular attention to the materials and their manufacturing process. Each technique shows advantages and disadvantages and our aim is to highlight a possible trade-off between flexibility, ergonomics, low power consumption, integration and eventually autonomy.
Notes:
This article describes the current state and the expected future demand for wearable electronic devices.
This would be the best article to read first when familiarizing oneself with wearable electronics, specifically when interested in systems to be integrated into cloth or other non-rigid wearable means.
This article explains the use of embroidery machines, as well as many other methods for making wearable devices integrated into cloth.
There is a useful table which describes the electrical properties of metal monofilaments fibers.
He H, Chen X, Ukkonen L, Virkki J. Textile-integrated three-dimensional printed and embroidered structures for wearable wireless platforms. Textile Research Journal. 2019;89(4):541-550. doi:10.1177/0040517517750649
Abstract
In this paper, we present fabrication and performance evaluation of three-dimensional (3D) printed and embroidered textile-integrated passive ultra high frequency radio frequency identification (RFID) platforms. The antennas were manufactured by 3D printing a stretchable silver conductor directly on an elastic band. The electric and mechanical joint between the 3D printed antennas and microchips was formed by gluing with conductive epoxy glue, by printing the antenna directly on top of the microchip structure, and by embroidering with conductive yarn. Initially, all types of fabricated RFID tags achieved read ranges of 8–9 meters. Next, the components were tested for wetting as well as for harsh cyclic strain and bending. The immersing and cyclic bending slightly affected the performance of the tags. However, they did not stop the tags from working in an acceptable way, nor did they have any permanent effect. The epoxy-glued or 3D printed antenna–microchip interconnections were not able to endure harsh stretching. On the other hand, the tags with the embroidered antenna–microchip interconnections showed excellent wireless performance, both during and after a 100 strong stretching cycles. Thus, the novel approach of combining 3D printing and embroidery seems to be a promising way to fabricate textile-integrated wireless platforms.
Notes
This article illustrates the use of RFID technology in wearable electronics.
RFID lends itself very well to wearables because it does not require a battery. This makes the device smaller and more durable.
Embroidery does not play a huge role in this research, but it is directly compared with epoxy and 3D printing for connecting and holding sensors in place.
Sun D, Chen M, Podilchak S, et al. Investigating flexible textile-based coils for wireless charging wearable electronics. Journal of Industrial Textiles. 2020;50(3):333-345. doi:10.1177/1528083719831086
Abstract
Smart and interactive textiles have been attracted great attention in recent years. This research explored three different techniques and processes in developing textile-based conductive coils that are able to embed in a garment layer. Coils made through embroidery and screen printing have good dimensional stability, although the resistance of screen printed coil is too high due to the low conductivity of the print ink. Laser cut coil provided the best electrical conductivity; however, the disadvantage of this method is that it is very difficult to keep the completed coil to the predetermined shape and dimension. The tested results show that an electromagnetic field has been generated between the textile-based conductive coil and an external coil that is directly powered by electricity. The magnetic field and electric field worked simultaneously to complete the wireless charging process.
Notes
Self-charging of wearable devices will be a key area of study and development.
The movement and environment that wearable devices will be subjected to give the potential for energy generation.
This article details how embroidery can be used as a manufacturing method to produce charging systems.
The researchers mentioned the different threads they tried using in the embroidery process and the issues they faced with each.
This setup places the conductive thread in the upper bobbin and regular thread in the lower bobbin.
There is an approximation for length of thread used in each of the loops that the thread experiences when weaving through the layer of fabric.
Yuanfang Zhao, Jiahui Tong, Chenxiao Yang, Yeuk-fei Chan and Li Li, “A simulation model of electrical resistance applied in designing conductive woven fabrics,” Textile Research Journal 86(16), Aug. 2018, doi: 10.1177/0040517515590408.
Abstract
Numerous studies have performed analyses of knitted fabric integrating conductive yarn in textile-based electronic circuits, some of which established simulative models such as the resistive network model for knitting stitches. Compared to conductive knitted fabrics, limited studies have been presented regarding the resistive theoretical model of conductive woven fabric. In this paper, a simulation model was derived to compute the resistance of conductive woven fabric in terms of the following fabric parameters: structure, density and conductive yarn arrangement. The results revealed that the model is well fitted (P value<0.01) and can predict the resistance of woven fabrics, which makes it possible to estimate the fabric parameters and thus to meet the required resistance. Based on this model, thermal conductive woven fabric with maximum energy management and cost control can be efficiently designed.
Notes:
The resistances of conductive textiles are studied, which can provide insight to the resistance of conductive thread used by the embroidery machines. The effects of stress on the threads as well as the patterns or curves the threads are subjected to are studied. As the threads are pulled in tension, their resistance increases.
A useful outtake from this article is the study of how increasing the number of contacts or short circuits between wires decreases resistance. With the embroidery machine, as the conductive threads are placed, there will need to be care taken to control the placement of stitches. For example, when making a resistor out of embroidered thread, the number of contacts between wires will control the resistance to current through that pattern of thread.
Several weave patterns are studied, which will be important for embroidery if the conductive thread is used as the upper thread. The upper thread in an embroidery machine is subjected to a lot of bending which would resemble the bending these threads are subjected to in weaving.
The testing methods used in this article could be useful to use as a basis for forming a testing method for embroidered wire. It would be beneficial to conduct a similar series of testing specifically on embroidered wire to better understand it's properties.
Wicaksono I, Tucker CI, Sun T, et al. A tailored, electronic textile conformable suit for large-scale spatiotemporal physiological sensing in vivo. npj Flexible Electronics. 2020;4(1):5. doi:10.1038/s41528-020-0068-y
Abstract
The rapid advancement of electronic devices and fabrication technologies has further promoted the field of wearables and smart textiles. However, most of the current efforts in textile electronics focus on a single modality and cover a small area. Here, we have developed a tailored, electronic textile conformable suit (E-TeCS) to perform large-scale, multimodal physiological (temperature, heart rate, and respiration) sensing in vivo. This platform can be customized for various forms, sizes and functions using standard, accessible and high-throughput textile manufacturing and garment patterning techniques. Similar to a compression shirt, the soft and stretchable nature of the tailored E-TeCS allows intimate contact between electronics and the skin with a pressure value of around ~25 mmHg, allowing for physical comfort and improved precision of sensor readings on skin. The E-TeCS can detect skin temperature with an accuracy of 0.1 °C and a precision of 0.01 °C, as well as heart rate and respiration with a precision of 0.0012 m/s2 through mechano-acoustic inertial sensing. The knit textile electronics can be stretched up to 30% under 1000 cycles of stretching without significant degradation in mechanical and electrical performance. Experimental and theoretical investigations are conducted for each sensor modality along with performing the robustness of sensor-interconnects, washability, and breathability of the suit. Collective results suggest that our E-TeCS can simultaneously and wirelessly monitor 30 skin temperature nodes across the human body over an area of 1500 cm2, during seismocardiac events and respiration, as well as physical activity through inertial dynamics.
Notes:
This is a great example of the potential use of wearable electronic devices.
An in-depth review of this specific application.
Instead of embroidery, they weave or knit the conductive materials into the fabric.
Fig 1 is a great view of what these sensing devices look like and how they are placed in the clothing.
Other useful links and information (non peer reviewed)
This gives a general table of material unit resistances. Note the resistances of Silver, Copper, and Stainless Steel as those are some of the most commonly used in embroidered or fabric wearable electronic systems.
