## 3 Results  
Operational Insights for Compound Dosing, Quantified Concentration Gradients, Flow Distribution Patterns, and Transforming Well-to-Well Exposures  
To quantify fluid flow patterns, we surveyed a single row (1-of-8) over 10 consecutive dosing periods (Figure 4(a1,b2)). Acellular wells are well 1 (source/dose), well 2 (fluid regulator), and well 12 (sink/wick). Cell cultures being wells 3-11. For cell seeding and \(\upmu\)channel flow preparation, the entire row is filled with shared nutrient media (e.g., uncolored and clear). When a bolus drug is placed into well 1, the drug flows toward well 12, creating a dilution gradient of compound flow from high-to-low concentrations (Figure 4(a1-a3), compound dilutions). Then, if cell metabolites are generated in downstream culture chambers, these cell byproducts are pushed towards well 12, hypothetically creating low-to-high concentrations (Figure 4(a2,a3), generated metabolites). To track parent drug exposures and quantify real-time shifts of concentrations, FITC is used as a drug surrogate with FITC concentration gradients monitored/quantified using a microplate reader, ex485/em525 [23]. The Data Table in Figure 4(b2) shows that 1 \(\upmu\)M FITC is dosed into the source well (well 1) on 10 chronological iterations. Dose \"0\" is before FITC dosing (i.e., baseline media) measuring the common and shared nutrient media that is identical across the entire row, wells 3-11, quantified \"0.000\". Dose 1 shows well 3 at 0.445 (44.5% of 1 \(\upmu\)M FITC dose), well 4 at 0.322 (32.2%), and well 11 at 0.00 (0%), signifying an initial gradient of dose-flow from wells 3-11. A 5 th dose displays well 3 at 0.674 (67.4% of 1 \(\upmu\)M FITC dose) and well 4 at 0.650 (65.0%) and well 11 at 0.214 (21.4%). A 10 th dose displays well 3 at 0.674 (67.4% of 1 \(\upmu\)M FITC dose), well 4 at 0.674 (67.4%), and well 11 at 0.624 (62.4%). The distribution of FITC increases after each dose, higher from left-to-right. Quantified data can be assessed across one entire row for wells 3-11 (Figure 4(b2); horizontal display) or within 1 culture well over time periods (Figure 4(b2); vertical display). For individual culture wells (vertical display), time-dependent exposures are portrayed as escalating linescans, i.e., flow timelines/well (Figure 4(b1)). During the 10-dose study, well 3 experiences the quickest/highest exposure (i.e., asymptotic with steepest slope), well 7 depicts an approximate linear exposure pattern, and well 11 foretells a delayed exposure dynamic (i.e., delayed increase). Subsequently, fully developed linescans progress into natural logarithm, linear, and delayed exponential growth [23]. Associatively, cumulative well exposures are depicted in Figure 4(b3). Accrued exposures are similar to a radiation exposure model with area-under-the-curve (AUC) quantifications. Well 3 has the highest AUC at 6.21, wells 7 and 8 with midrange values of 4.26 and 3.60, and well 11 being the  
Figure 3: Standard operating procedure (SOP) for 1-drug study (n = 3). (**a**) Preparation and cell seeding. (**b**) First dose into well 1. (**c**) Re-dosing into well 1.  
lowest at 2.69. From this single-row study, Figure 4(b2), ninety-nine (99) datapoints are generated to establish a trending assessment of non-linear compound concentrations over time and location. From this dosing study, by way of extrapolation, one device equates to 8 rows \(\times\) 99 = 792 exploitable datapoints.