The robotic pill comprised three modular compartments each designed for unique purposes as shown in Figure 2a, including the use of (i) s three sampling modules that allow the collection of different biomarkers in an absorbent trapping matrix while letting the biofluid pass through it, (ii) a porous membrane that enables the exclusion of larger objects (> 5 µm) in the collection chamber and (iii) a magnetic core embedded in the structure that aims to provide directed locomotion and retention of the robotic pill potentially at targeted regions of the body. The robotic pill prototype was fabricated using a laser cutter to cut optically clear and poly(methyl methacrylate) (PMMA) sheets (1.5-mm thick) into the pill shape with space for placing a 3-mm neodymium magnet and three rectangular collection chambers (3 x 2 mm, 9 µL per chamber). The plastic backbone provides mechanical stability to the pill structure and holds the absorbent material in the collection chamber. A double-sided adhesive film was cut in the shape of the robotic pill backbone and used to adhere a polycarbonate membrane with 5 µm
pores to the plastic backbone. Sodium polyacrylate powder (absorbent) was placed in the collection chamber before sealing the collection chambers on both sides using the polymeric membrane. (Figure S1). Integrating absorption, delayed opening of the collection chamber, and docking control into a single device could potentially enable the isolation of biomarkers within the hard-to-access regions of the body, as shown in schematic illustrating the retention of a robotic pill in the small intestine through magnetic retention (Figure 2b). In addition, the pill was designed to be comparable to FDA-approved ingestible device standards, as its measurements are 16 mm in length, 6 mm in diameter and 1.5 mm in thickness.\cite{Sayeed2015} (Figure 2c). The sampling capability of the pill is illustrated by Figure 2d, where the photographs show a robotic pill before (top) and after (bottom) immersion (5 min) in water colored in blue dye, where each of the three collection chambers retained the liquid captured by the absorbent material.