*2.1. Preparation of Aligned Polycaprolactone Electrospun Fiber Mat Constructs*

Aligned polycaprolactone (PCL) fiber mats were prepared by electrospinning onto a rotating mandrel, as described previously [25]. Briefly, 5 wt% PCL (Mn 70,000–90,000, Sigma-Aldrich, St. Louis, MO, USA) solution in 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) (>99% purity; Oakwood Products, Inc., Columbia, SC, USA) was electrospun at 4 mL/h at a 20 cm needle-to-collector distance [26]. The rotating mandrel was set to maintain a linear velocity at the collecting surface of 15 m/s. Fiber mat thickness was varied from 50, 100 and 200 microns by spinning for ~45 min, ~1 h 30 min and ~4 h, respectively. Fiber mats were spun either directly onto a supporting material or across an annular gap (Figure 1). Fiber mats were rendered hydrophilic for cell culture by air plasma treatment (Harrick Plasma, Ithaca, NY, USA) under vacuum at ~700 mTorr and with a plasma radio frequency of 8–12 MHz for 3 min. Fiber mats were used immediately in experiments.

**Figure 1.** Schematic of Electrospun Fiber Mats. Electrospun fiber mats (EFMs) were either spun directly onto a stiff support (**A**), spun across a gap (**B**), or spun unto foil, removed, and then fixed across a gap (**C**).
