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Simultaneous Digital Communication and Deformation Sensing over a Single Stretchable Interconnect
Yuji Isano, Hiroki Ota
TL;DR
Stretchable hybrid electronics rarely use deformation itself to convey mechanical state, limiting integrated communication and strain sensing. This paper introduces a single-interconnect architecture that combines digital communication with deformation sensing, detecting both without crosstalk and achieving −6.7 mV/strain% sensitivity while preserving communication up to 284% elongation.
Problem
Existing stretchable hybrid devices generally do not exploit deformation to encode mechanical information, while rigid devices cannot deform to provide it.
Method
The study amplitude-modulates UART digital signals transmitted between rigid nodes using strain-induced resistance changes in stretchable liquid-metal interconnects.
Results
−6.7 mV/strain% sensitivity was achieved using a single wire, while communication functionality remained up to 284% average elongation (n = 3).
Takeaways & Limitations
The architecture demonstrates simultaneous digital communication and deformation sensing without crosstalk in stretchable hybrid devices.
Takeaways & Limitations
The proof of concept used bulk devices, leaving further development for future studies.
Abstract
from arXiv · showhide
Stretchable hybrid electronics integrate rigid solid-state electronics with stretchable materials and structures to achieve both high deformability and stable electronic performance. However, most existing systems treat stretchability only as a mechanical attribute without exploiting device deformation to encode its own mechanical state. This problem arises from adapting conventional rigid circuit architectures to stretchable substrates, affording a loss in compatibility with the sensors required for strain measurement. This study addresses this issue by proposing a communication-integrated deformation sensing architecture for stretchable hybrid devices. In the proposed approach, standard universal asynchronous receiver-transmitter digital signals transmitted between rigid nodes are amplitude-modulated by strain-induced resistance changes in stretchable liquid metal interconnects. By reading both amplitude changes and digital patterns, the system enables simultaneous digital communication and self-deformation sensing without requiring additional stretchable sensing elements. The architecture is demonstrated in a multi-node system and applied to wearable sensing and self-deformation mapping devices. By extending the integration of rigid circuits and soft elements from the hardware level to the system level, this study provides a novel design paradigm for stretchable electronic systems that inherently utilize their own deformation as functional information.
1. Introduction
Stretchable hybrid devices can exploit their own deformation as functional information, but conventional architectures require dedicated sensors that consume space and reduce reliability. This study introduces a communication-integrated architecture that uses stretchable wiring for both UART communication and strain measurement.
- Problem: Conventional stretchable hybrid architectures rarely convert their own deformation into information while performing primary electronic functions.The devices have mainly used stretchability to improve attachment freedom and conformability.
- Motivation: Stretchable devices can encode their shape, posture, or motion through deformation, a function fundamentally difficult for rigid devices.Their deformation can occur in unison with contacted objects and serve as information.
- Problem: Dedicated deformable sensing elements consume limited mounting area and reduce reliability through additional components, wiring, and loose contacts.These constraints can cause failures or signal degradation and cannot be resolved simply by adding flexible components or layers.
- Contribution: The proposed architecture uses each stretchable wire for inter-rigid communication and strain sensing without adding elastic measurement elements.It functionalizes the conductor’s intrinsic resistance–strain response as the digital communication modulation mechanism.
- Architecture: UART data are amplitude-modulated by stretchable-wire resistance, allowing a decoder to read both digital data and inter-node distance variation through the same wiring.The system encodes measurements into digital packets, modulates the output signal, and reads its amplitude and data at the far end.
2. Results and Discussion
The results demonstrate a stretchable architecture that simultaneously transmits UART data and senses deformation through resistance changes in a single communication line. Multi-node demonstrations, protective structures, and wearable applications establish communication, sensing, durability, and mapping capabilities.
- Communication-integrated deformation sensing: The system integrates a transmitter, deformation-sensitive communication line, and receiver-side multi-decoder on a flexible PCB bonded to a stretchable substrate.Sensor measurements are packetized and transmitted using an existing UART communication system.
- Multi-node communication: Multi-decoder and three-unit serial-relay tests transmitted digital data without loss or distortion while independently detecting wiring strains without crosstalk.Deformation sensing also extended to sections not directly connected to the master readout unit, with minimal error.
- Communication-integrated deformation sensing: Approximately −6.7 mV/strain% sensitivity at VCC = 3.3 V was maintained from 4,800 bps to 115,200 bps, while deformation-rate changes up to 200%/s were observed.The reported sensitivity was unaffected by communication speed, and stable resistance changes persisted after 200 deformation cycles.
- Device demonstrations: Wearable demonstrations simultaneously measured finger pressure and joint bending, while a three-dimensional mapping system transmitted unit tilt and deformation data under 100% deformation.The demonstrations included force changes during gripping, throwing, and other finger movements without delay.
- Versatility and limitations: The architecture supports analog-to-digital sensors beyond resistive types, can use flexible circuit units with high-performance components, and is extensible in principle to I2C and SPI protocols.The reported limitations include noise from time-based random sampling and demonstrations comprising bulk devices with serial connections of up to three nodes.
3. Conclusions
The proposed architecture uses deformation-induced resistance changes in a single stretchable interconnect to simultaneously transmit digital signals and sense strain. It maintains communication during substantial elongation while supporting compact, compatible integration with rigid circuits.
- Architecture and operation: The architecture amplitude-modulates digital communication signals according to wiring-resistance changes caused by deformation, then demodulates them through an existing digital interface.Distance changes between rigid elements are encoded through strain-dependent signal-voltage changes.
- Architecture and operation: Digital and analog signals were detected without crosstalk, enabling simultaneous single-wire strain sensing and digital-signal reception.Strain detection reached a sensitivity of −6.7 mV/strain%.
- Demonstrated performance: Communication functionality was maintained up to an average elongation of 284% (n = 3).The performance was attributed to the layered rigid–soft hybrid structure.
- System-level integration: Using one stretchable interconnect for multiple purposes mitigates limited mounting area, facilitating higher device density and additional flexible circuit integration.The architecture combines existing rigid circuits and communication protocols for reproducibility, versatility, and compatibility with rigid circuits.
- Limitations and future work: The proof-of-concept measurement circuit used bulk devices, while future work will develop smaller, more integrated devices with architectures optimized from the IC design stage.The stated future direction targets higher functional integration for stretchable hybrid devices.
4. Methods · W. Jeong, J. Kang, Science 2022, 378, 637.
The methods establish the communication and strain-measurement evaluation setup, fabricate stretchable hybrid devices, and demonstrate pressure-sensing and deformation-mapping implementations. Measurements combine circuit instrumentation, mechanical testing, inertial sensing, reference-based strain estimation, and software visualization.
- Development and Evaluation of a Multimodal Strain Measurement and Communication System:: The evaluation system used flexible transmitter and relay circuits with an ADA4528 operational amplifier, 8-bit ADC, UART communication, and microcontroller-integrated comparator circuitry.The multi-decoder used an LT1678 operational amplifier, NJU7109F comparator, UART receiver, and 12-bit ADC on a Raspberry Pi Pico board.
- Development and Evaluation of a Multimodal Strain Measurement and Communication System:: Strain-modulated communication waveforms were recorded with a PicoScope 2205A, while resistance–amplitude relationships were verified using a breadboard inverting-amplifier circuit.Device deformation was induced with a single-axis stage, and circuit simulations were performed using LTSpice.
- Physical Characteristics of the Device:: Physical characteristics were evaluated through COMSOL Multiphysics simulations, digital image correlation visualization, and strain–force measurements from an EZ-LX tensile testing machine.These methods addressed nonlinear strain characteristics and the actual device strain state.
- Simultaneous Measurement of Finger Pressure and Deformation:: For simultaneous finger-pressure and deformation measurements, a flexible pressure sensor was attached with the control circuit, rolled into a ring, and read through a voltage divider.The ring device connected by wire to an external multi-decoder, with acquired data processed and visualized using Python.