*2.2. Specimen Characterization*

The 3D structure of PEO coating, including a surface, an internal structure, an aluminum/coating interface, and a fracture cross section, was obtained by an electrochemical dissolution method, a layer-by-layer thinning method, and a cross-cutting method. Among them, the internal structure was obtained by exfoliating the outer layer using a single scratch tester (WS-2005, Lanzhou Institute of Chemical Physics, CAS, Lanzhou, China). The scratch tests were made with a diamond indenter (120◦ cone with a tip with a radius of 200 μm) under a loading rate of 50 N/min, a loading range of 0–100 N, and a scratch length of 10 mm. The free-standing coating was obtained by removing the substrate using an electrochemical method [13,14]. The specific operation process is as follows: specimens with PEO coatings were firstly polished from one side to a ~0.5 mm thickness. The specimen was immersed partly into a 3.5 wt % NaCl solution as the anode and a stainless-steel cell as the cathode, which was connected with a direct-current power supply with an operating voltage of 15 V. The aluminum had been dissolved completely when the current decreased to zero. A free-standing coating was obtained, cleaned in deionized water, and left to dry naturally.

The surface, internal structure, coating/substrate interface, and fractured cross-sectional morphologies of the PEO coatings were observed by a field emission gun SEM (FE-SEM, Nova Nano SEM 450, Thermo Fisher Scientific, Hillsboro, OR, USA). Chemical compositions of the PEO coatings were analyzed by energy dispersive spectroscopy (EDS, INCA 250, Oxford Instruments, Oxford, UK) equipped on the FE-SEM system. The high voltage and spot size were set to 15 kV and 3.0, respectively. During EDS semi-quantitative analysis, five measurements were taken randomly, and the average value was taken. The standardless quantitative analysis and the XPP correction method were used for the atomic percent calculation of various elements during EDS analysis. For the elements investigated in this study (O, Al, Si, and P), the total relative uncertainty was estimated to be ±5%. The phase composition of the coatings was analyzed by X-ray diffraction (XRD, D8-Advance, Bruker, Karlsruhe, Germany) using Cu Kα radiation operated at 40 kV and 40 mA in a range from 10◦ to 80◦ with a step size of 0.02◦. Before XRD analysis, free-standing coatings were obtained using the electrochemical method and then ground into powder samples using the mortar. The maximum height difference between the peaks and valleys of the coating was characterized by a 3D digital video microscope (KH-7700, Hirox Co., Ltd., Tokyo, Japan). The size of the 3D scanning region in this work was 295 μm × 220 μm. The 3D scanning resolution was 1 μm. The resolution of *Z*-axis step motor was 0.05 μm/pulse.


**4. Perspective**

The authors of the perspective, Krist V. Gernaey et al. [21], emphasize that despite the benefits of continuous over-batch bioprocessing, its adoption has lagged, with few exceptions. However, the batch manufacturing paradigm's dominance in the industry for reasons such as "batch processing is familiar and works very well" cannot be sustained in the long term, given the new biomanufacturing challenges. Moreover, the industry-held perception of complexity in continuous bioprocessing is becoming obsolete as more and more new technologies and solutions continually improve the situation. Several academicand industry-led consortia are working to improve the perception regarding continuous bioprocessing by bringing the questions to the correct stakeholders who can address them. The training provided by these initiatives to the top management of the companies is playing an essential role in changing the perception and, at the same time, also creating new scientists and operators that can understand and respond to a new set of operational challenges. However, wider adoption of continuous bioprocessing will only be possible if the technical, management, and regulatory gaps are acknowledged. This paper argues that concerted efforts focusing on technology, management, and regulatory aspects are abridging them.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would like to acknowledge the support of CEPIMA (UPC) Barcelona, Spain.

**Conflicts of Interest:** The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


**2.1. Existing research on determinants of fiscal sustainability**

Research on the financial issues of the welfare state is a classic theme of the welfare state. This is divided into studies focusing on economic factors and studies focusing on institutional factors.


**8. Acknowledgments**

Authors would like to show their sincere gratitude to CIMA research group from University of Vigo, Veterinary Clinic FAUNA from Vigo, medical device manufacturers LAFITT and SURGIVAL from Valencia. Without their collaboration, this manuscript would not be possible.