Talking Ink: A Flow-Based Multi-Molecule Molecular Communication Testbed for Effective Channel Modeling and Detector Benchmarking

2026-07-22

AI Summary

Existing molecular communication testbeds struggle to simultaneously achieve physical realism, reproducibility, and practicality, thereby hindering accurate channel modeling and detector evaluation. This work presents the first real-time, multi-molecular communication experimental platform based on colored inks, employing cyan, magenta, and yellow inks as orthogonal signaling molecules. Multi-molecular on–off keying (OOK) modulation is realized via micro-pumps and multi-needle injection within a flowing channel, while an unobtrusive spectrometry-based receiver captures end-to-end color trajectories. Building upon this setup, the study introduces a modified energy difference detection (MEDD) scheme and establishes a reusable framework for channel modeling and detector assessment. Experimental results demonstrate that MEDD achieves a bit error rate as low as 0.76% without prior channel knowledge—approaching the near-optimal MMSE performance of 0.71%—and enables zero-error transmission at rates of 6 bit/s and 3 bit/s over distances of 8 cm and 24 cm, respectively, after optimization.

Abstract

Practical molecular communication (MC) testbeds are essential for translating theoretical concepts toward future applications while retaining physical realism, accessibility, and experimental repeatability. We present a flowbased MC experimental system for real-time multi-molecule (MUMO) transmission using cyan, magenta, and yellow inks as distinguishable molecule-like signaling carriers. Three micropumps and a multi-needle injection system release the inks into a background-flow channel, and a non-invasive spectral sensor estimates received color traces at variable transmitter-receiver distances. The platform supports measurements of isolated-pulse responses across distances. We interpret these measurements as effective end-to-end channel impulse responses (CIRs) shaped by finite release, flow propagation, and receiver readout, and compare two compact model families. Both reproduce much of the dominant arrival timing and pulse shape, while late-tail mismatch remains the main limitation. We connect this channel characterization to communication performance through continuous MUMO on-off keying (OOK) payload measurements. The resulting retrospective benchmark with full-data parameter optimization includes traceonly and CIR-assisted methods. We introduce modified energydifference detection (MEDD), an adaptive extension of standard energy-difference detection (EDD). MEDD outperforms all other trace-only detectors with 34/4500 = 0.76% bit error rate (BER) and closely approaches the best overall minimum mean-square error (MMSE) result of 32/4500 = 0.71%. After targeted parameter tuning, the detector benchmark produces zero errors over the evaluated payloads at 6 bit/s over 8 cm and at 3 bit/s over 24 cm. Overall, the results establish the platform as a reusable experimental setup for effective channel modeling, practical detector benchmarking, and future multi-molecule networking experiments.

Problem

• molecular communication
• multi-molecule
• channel modeling
• detector benchmarking
• experimental testbed

Innovation

• molecular communication
• multi-molecule signaling
• flow-based testbed
• channel impulse response
• modified energy-difference detection