A TWO-LAYER SILK FIBROIN NANOFIBROUS MATERIAL: FABRICATION, SPECIFIC PROCESS INDICATORS AND AN INVESTMENT-BASED TECHNO-ECONOMIC ASSESSMENT OF LABORATORY-SCALE PRODUCTION

Abstract

Techno-economic assessments of electrospun materials rarely go beyond a unit-cost calculation and a margin, which can conceal whether the capital employed is recovered at all. This work fabricates a two-layer silk fibroin nanofibrous material, characterises the process through specific indicators, and then assesses it with investment criteria rather than accounting margins alone. The material is produced in two stages: a water-soluble first layer from a 16% poly(vinyl alcohol) solution, which reduces adhesion to the substrate, and a second layer from a composite of 40% silk fibroin solution and 60% poly(vinyl alcohol) solution. One production cycle converts 5 mL of solution into approximately 0.75 g of dry polymer over 0.065 m², an areal density of about 11.6 g m⁻². Separating the cost structure shows that fixed costs account for 89.6% of total cost, giving a break-even point of 529 units per month, that is 89.9% of installed capacity, and a financial safety margin of only 10.1%. Investment analysis is markedly less favourable than the accounting margin of 10.1% suggests: the simple payback period is 26.5 years against a 10-year equipment life, the cash payback period including the depreciation add-back is 7.3 years, and the net present value at a 10% discount rate over ten years is negative. Doubling throughput, which is achievable by fitting a multi-emitter head without additional machine capital, changes the outcome decisively, and the maximum additional capital expenditure that such a modification could justify is quantified. An occupational-risk assessment using a probability × severity matrix and an environmental-aspect analysis complete the evaluation.