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Microdroplet-Based Communications with Frequency Shift Keying Modulation

Eren Akyol, Aysa Azmoudeh, Iman Mokari Bolhassan, Pelin Kubra Isgor, Murat Kuscu

TL;DR

This work tackles the limitations of diffusion-based molecular communications by implementing microdroplet-based signaling in a microfluidic platform. It employs a flow-focusing transmitter to generate sub-100 μm water-in-oil droplets and encodes information with 4-FSK by controlling the dispersed-phase pressure, with a video-based receiver quantifying arrival frequencies. The study demonstrates stable, distinguishable frequency levels and near-error-free symbol decoding for longer symbol durations, with a measured trade-off at shorter durations (e.g., 20 s vs 12 s). The results highlight the potential for biocompatible, compartmentalized carriers in intrabody networks and IoBNT, with extensions to vesicle-like carriers such as liposomes or polymersomes for higher data rates and robustness.

Abstract

Droplet-based communications has been investigated as a more robust alternative to diffusion-based molecular communications (MC), yet most existing demonstrations employ large "plug-like" droplets or simple T-junction designs for droplet generation, restricting modulation strategies and achievable data rates. Here, we report a microfluidic communication system that encodes information via the generation rate of sub-100 $μ$m water-in-oil microdroplets using a microfabricated flow focusing architecture. By precisely tuning the flow rate of the dispersed-phase (water) via a pressure-regulated flow controller, we implement frequency shift keying modulation with four symbols (4-FSK). A high-speed optical detection and video processing setup serves as the receiver, tracking system response in the microfluidic channel across different symbol durations (20 s and 12 s) and quantifying error performance. Despite the miniaturized device and channel architecture, our experiments demonstrate programmable and reliable data transmission with minimal symbol errors. Beyond water-in-oil systems, the same encoding principles can be extended to other compartmentalized carriers (e.g., giant unilamellar vesicles, polymersomes) that can also be synthesized via flow focusing techniques, paving the way for biocompatible, robust, and high-capacity communication in intrabody networks and the emerging Internet of Bio-Nano Things.

Microdroplet-Based Communications with Frequency Shift Keying Modulation

TL;DR

This work tackles the limitations of diffusion-based molecular communications by implementing microdroplet-based signaling in a microfluidic platform. It employs a flow-focusing transmitter to generate sub-100 μm water-in-oil droplets and encodes information with 4-FSK by controlling the dispersed-phase pressure, with a video-based receiver quantifying arrival frequencies. The study demonstrates stable, distinguishable frequency levels and near-error-free symbol decoding for longer symbol durations, with a measured trade-off at shorter durations (e.g., 20 s vs 12 s). The results highlight the potential for biocompatible, compartmentalized carriers in intrabody networks and IoBNT, with extensions to vesicle-like carriers such as liposomes or polymersomes for higher data rates and robustness.

Abstract

Droplet-based communications has been investigated as a more robust alternative to diffusion-based molecular communications (MC), yet most existing demonstrations employ large "plug-like" droplets or simple T-junction designs for droplet generation, restricting modulation strategies and achievable data rates. Here, we report a microfluidic communication system that encodes information via the generation rate of sub-100 m water-in-oil microdroplets using a microfabricated flow focusing architecture. By precisely tuning the flow rate of the dispersed-phase (water) via a pressure-regulated flow controller, we implement frequency shift keying modulation with four symbols (4-FSK). A high-speed optical detection and video processing setup serves as the receiver, tracking system response in the microfluidic channel across different symbol durations (20 s and 12 s) and quantifying error performance. Despite the miniaturized device and channel architecture, our experiments demonstrate programmable and reliable data transmission with minimal symbol errors. Beyond water-in-oil systems, the same encoding principles can be extended to other compartmentalized carriers (e.g., giant unilamellar vesicles, polymersomes) that can also be synthesized via flow focusing techniques, paving the way for biocompatible, robust, and high-capacity communication in intrabody networks and the emerging Internet of Bio-Nano Things.

Paper Structure

This paper contains 8 sections, 4 figures.

Table of Contents

  1. Introduction
  2. Materials and Methods
  3. Transmitter Design and Fabrication
  4. Experimental Setup
  5. Results and Discussion
  6. Characterization of Frequency Modulation
  7. Communication Experiments
  8. Conclusion

Figures (4)

  • Figure 1: (a) Top-view layout of the flow-focusing microfluidic chip design, showing the main propagation channel, side channels, and orifice dimensions. (b) Experimental setup for microdroplet-based microfluidic communications.
  • Figure 2: (a) Visualization of sub-$100$ µ m w/o droplet formation at various dispersed-phase pressures (applied at the corresponding inlet) in the flow-focusing microfluidic channel. The water phase is tinted with a commercial dye for clarity, and pressures (in mbar) decrease from top to bottom. (b) Measured relationship between dispersed-phase pressure and droplet generation frequency, illustrating a monotonic increase in droplet frequency with increasing pressure.
  • Figure 3: (a) Thresholding of droplet arrival frequencies at selected dispersed-phase pressures. The dashed lines indicate the frequency boundaries for mapping each pressure setting to a unique symbol, Sym-{1,2,3,4}. (b) Time-domain intensity plots of droplet arrival at four different pressures.
  • Figure 4: Receiver response to randomly generated $20$-symbol sequence with intervals of (a) $20$ s and (b) $12$ s, where the background colors represent the transmitted symbols, and the small squares denote decoded symbols.