Open-source, Low-cost 3D-Printable Testbed for Optical-based In-body Communication Research
Description
Typically, studies on optical wireless communication (OWC) employ high-end components, including an optical bench and its accessories. Using such properties in in-body OWC studies presents challenges, i.e., from a cost, ergonomic, and technical perspective. The optical bench is bulky, rigid, and unaffordable, with a large footprint that is oversized for such short-range and confined beam requirements. In-body OWC is sensitive to optical alignment and requires shielding experiments from ambient light to mitigate light interference (e.g., normal laboratory room lighting). Achieving a misalignment-free setup requires careful manual tuning, which consumes setup time and is susceptible to errors. These issues become worse in dark environments, where experiments are conducted, potentially causing eye strain and discomfort after long testing periods. Thanks to the availability of consumer-grade 3D printing technologies, an alternative testbed can be produced more affordably than commercial products, and with greater openness. Here, we propose a 3D-printable testbed for an in-body OWC experiment that offers several benefits, including low cost, open-source design, ambient light shielding, and facilitates faster and more accurate optical alignment setup, thereby reducing setup time. Additionally, the proposed testbed allows researchers to perform experiments under normal lighting conditions without compromising measurement accuracy. As a result, this significantly improves researcher comfort and eye health by eliminating the need to turn off laboratory lighting. The repository includes the following files, all of which are openly shared to support replication by the research community: 1. 3D-printable design files: contains 3D printable models for the top mount, chassis, and leg supports (3 mm and 20 mm). Files are support-free for standard PLA printing. 2. Illustrative figures of the build instructions. 3. Supplementary Data 1: Contains (a) raw data in XLS files, which are empirical data of optical power measurements of NIR LED 850 nm and 810 nm under controlled experiments (i.e., varied drive currents and ambient lighting conditions: ON v.s. OFF). The testbed enables reproducible experiments under both ambient light ON and OFF conditions. We also provide MATLAB scripts for statistical analysis and plotting with error bars under 850 nm and 810 nm NIR LEDs. The measurement employs a Thorlabs optical sensor (S121C) integrated with an optical power meter (PM100D), for which the settings can be found in [1], [2].
Files
Steps to reproduce
We provide detailed steps to reproduce the 3D-printable testbed in the "BUILD INSTRUCTIONS" file, which can be found on this webpage. Please read the mentioned file carefully. Step 1: Print All Components available on this webpage of the repository: Download and 3D print all required STL files using PLA filament. If you encounter any issues with the file, please contact the authors. Step 2: Mount the NIR LED: Insert the mounted Thorlabs LED into the central circular hole in the top plate. Ensure the LED pad is insulated (for example, using tape) to avoid a short circuit when in contact with moist samples. The LED’s optical emission surface must remain exposed for unobstructed light transmission. Step 3: Attach Supporting Legs: Select and attach the interchangeable legs (e.g., 3 mm or 20 mm) underneath the chassis by inserting them into the four leg slots, much like LEGO bricks. The leg height depends on the photodetector type (e.g., 3 mm for S121C, 20 mm for PDA36A-EC). Step 4: Install the Photodetector: Place the photodetector (e.g., Thorlabs S121C or PDA36A-EC) into the bottom slot of the chassis. The holder ensures automatic alignment with the optical axis of the NIR LED above. An additional rectangular slot, located next to the photodetector, may be used to mount a photovoltaic (PV) cell for joint data and power transfer experiments, as in [3], [4]. Step 5: Place the Sample: Insert the optical phantom or ex vivo biological tissue into the inner compartment of the chassis. Ensure the sample is clean and free from dust, lies within the 110 mm × 110 mm area or less, but is large enough to cover the photodetector aperture. Place and press the top part, containing the NIR LED, into the chassis. ====================================================== References: [1] S. Fuada, M. Särestöniemi, M. A. N. Perera, and M. Katz, “Dataset of received optical power on pork meat for optical in-body communications studies,” Data in Brief, vol. 55, p. 110749, Aug. 2024, doi: 10.1016/j.dib.2024.110749. [2] S. Fuada, M. Särestöniemi, and M. Katz, “Measurement dataset of experimental in-body optical wireless communication test-bed for research purposes,” Data in Brief, vol. 61, p. 111765, Aug. 2025, doi: 10.1016/j.dib.2025.111765. [3] S. Fuada, M. Särestöniemi, and M. Katz, “Approach to joint wireless powering and communication with electronic implantable medical devices based on near-infrared light,” Opt. Continuum, OPTCON, vol. 4, no. 2, pp. 346–363, Feb. 2025, doi: 10.1364/OPTCON.550609. [4] S. Fuada, M. Särestöniemi, M. Katz, S. Fuada, M. Särestöniemi, and M. Katz, Perspective Chapter: Joint Energy Harvesting and Data Transfer for Medical Implants Exploiting Light - Concept and Preliminary Results. in The Challenges of Energy Harvesting. IntechOpen, 2025. doi: 10.5772/intechopen.1008464.
Institutions
- Oulun Yliopisto