A Novel Methodology for Economical Scale-Up of TiO₂ Nanotubes Fabricated on Ti and Ti Alloys

Table 2

Time and cost analysis comparing the two anodisation device designs. Wire-cut EDM (cutting Method 2) was adopted for calculating the costs due to its overall advantages. Staff rate of £20 per hour was incorporated as a typical wage for technical staff members trained to graduate level in the UK (prices current June 2018).

Descriptions	Version A	Version B
Number of specimens at one anodisation process	1 specimen	10 specimens
Preparation time per anodisation batch	a1 = 1.5 hr	b1 = 2 hr
Anodisation time per anodisation batch	a2 = 1 hr	b2 = 1 hr
Preparation time for 30 specimens	a3 = a1 × 30 = 45 hr	b3 = b1 × 3 = 6 hr
Anodisation time for 30 specimens	a4 = a2 × 30 = 30 hr	b4 = b2 × 3 = 3 hr
Total time for anodising 30 specimens	a5 = a3 + a4 = 75 hr	b5 = b3 + b4 = 9 hr
Total labour time per anodised specimen	a6 = a5/30 = 150 min	b6 = b5/30 = 18 min
% increase in time efficiency compared to version A (A/B  100)	—	833
Total labour cost per specimen (staff rate £20/hour)	a7 = a6 × 20 = £ 50.00	b7 = b6 × 20 = £ 6.00
Estimated cost per usable specimen, dT2 (carried from Table 1)	£ 1.39	£ 1.39
Estimated price of one complete anodised specimen	a7 + dT2 = £ 51.39	b7 + dT2 = £ 7.39
% increase in cost efficiency compared to version A [A/B  100]	—	695%

Specimen preparation time includes deburring, degreasing, assembling, lacquering, cleaning after anodisation, disassembling, sonicating, and packing for sterilisation after anodisation. “30 specimens” were used as a standard quantity needed for a fundamental in vitro statistical assessment, i.e., biocompatibility assays on anodised specimens of different nanotube diameters.