It might be a long time since you last needed to scribble a phone number on the back of your hand, but those days could be coming back thanks to new wearable touch panels.
Smart textiles based on nanomaterials have been taking off in recent years as researchers unveil their benefits in terms of flexibility and fabrication. A new example comes in the form of touch panels—a critical element for human–computer interactions, but one in which previous efforts have relied on sticky hydrogels to adhere to the skin or haven’t quite been in tune with how the human body naturally moves. To advance the potential of wearable touch panels, there is an essential need for comfortable, flexible, and skin-kind materials.
To address this need, researchers in China sandwiched a pressure-sensitive hydrogel between layers of silk—a natural fiber suitable for long-term skin contact. For conductivity, the top piece was coated in graphene nanosheets. When attached to electrodes and a data collection system this resulted in a real-time, pressure-responsive pad that could be worn on the arm.
Their results, published in ACS Nano, describe how users were able to control a computer game, sketch cartoons, and write words and notes from the flexible armband. The device was able to distinguish between intended touch and accidental motion such as slippage, and the sensing currents showed similar change trends under different limb movements.It also regained its original shape when deformed and released. This proof-of-concept iontronic touch panel offers the intriguing possibility of being able to sew smart touch panels into clothing.1
The work ties in nicely to other research from the team on bimorph actuators—or soft robotics. Photothermal soft actuators are especially interesting in smart textiles due to their cordless design and remote control. Currently, these are mostly based on films or paper, which inherently lack the flexibility and wearability of textiles. Their 2021 paper published in Nano Letters demonstrates a series of self-actuating devices, including a smart curtain that autonomously rolls when the sun rises, and a thermoregulating sportswear fabric created from MXene-modified polyamide filament—with breathable actuator stoma inspired by plants. With this, the yarns at the stomata bend to the left and right with ambient temperature increases, allowing more airflow through the fabric.2
The researchers have also published on the use of MXene mesh interwoven with biomimetic nanowires, enabling the design of flexible transparent electrodes and invisible camouflage electronics.3
Smart textiles are also needed on the other side of the human–computer interface, to help create robotic skin and a sense of touch for machines. Electronic gloves with multifunctional sensing capabilities hold promise in this arena. The key to this could be using low-cost CO2 laser engraving and electrospinning technology to fabricate sensors with vertical architecture, as well as interconnections designed to stretch in response to the deformation without affecting sensors performance. Work on these smart textiles could one day deliver smart fabrics that can simultaneously detect temperature, moisture, and pain with remote transmission of sensory data to the user.4
The authors say these innovations could inspire the next generation of wearable tech, from flexible keyboards and robotic sensors to wearable sketchpads and gaming controllers.
- Xu, R. et al. Skin-Friendly and Wearable Iontronic Touch Panel for Virtual-Real Handwriting Interaction. ACS Nano 2023, 17, 9, 8293–8302.
- Zhao H, et al. Wearable Sunlight-Triggered Bimorph Textile Actuators. Nano Lett. 2021, 21, 19, 8126–8134.
- Fan Q, et al. Biomimetic Hierarchically Silver Nanowire Interwoven MXene Mesh for Flexible Transparent Electrodes and Invisible Camouflage Electronics. Nano Lett 2022;22(2):740–50.
- Sharma S, et al. Stretchable and All-Directional Strain-Insensitive Electronic Glove for Robotic Skins and Human–Machine Interfacing. ACS Nano 2023, 17, 9, 8355–8366.