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Rekayasa: Jurnal Penerapan Teknologi dan Pembelajaran
Published by Universitas Negeri Semarang
ISSN : -     EISSN : 25276964     DOI : https://doi.org/10.15294/rekayasa
Core Subject : Education,
Other
REKAYASA journal publishes exciting articles from all fields of research and Engineering Science. The journals primary focus is on research practice and engineering processes utilizing biomass or factory waste. The engineering journal is an open-access peer-reviewed journal that publishes articles from all areas of Engineering and Science research.
Arjuna Subject : Umum - Umum
Articles 35 Documents
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Design and Feasibility Evaluation of Multimedia-Based Digital Learning Module for Women’s Body Proportion Drawing in Vocational Education Sri Listiani; M Noerharyono; Zulfira Farah Nubua
Rekayasa Vol. 23 No. 2 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i2.39695

Abstract

This study focuses on the design and feasibility evaluation of a multimedia-based digital learning module developed to support the teaching of women’s body proportion drawing in grade X vocational education. The module was designed as an interactive digital system integrating text, images, audio, and video to enhance user engagement and independent learning. The feasibility assessment was conducted by expert panelists using a mixed closed–open questionnaire based on module characteristics, including self-instruction, self-contained, adaptive, stand-alone, and user-friendly aspects, as well as media quality elements such as format, organization, attractiveness, typography, white space, and consistency. A descriptive quantitative approach with a one-shot case study design was employed to analyze the evaluation results. The findings indicate that the module achieved a score of 90.27% for module characteristics and 92.5% for media quality elements, with an overall feasibility score of 91.44%, categorized as “very good.” These results demonstrate that the developed module meets the criteria of a well-structured and functional digital learning system that can effectively support independent learning. This study contributes to the development of applied digital learning technology in vocational education by demonstrating how multimedia-based instructional design can enhance learning accessibility and usability. The findings also provide a reference for future development of technology-integrated learning media in technical and applied educational contexts.
Hydrometallurgical Recovery of Cobalt from Spent Lithium-Ion Battery (LiCoO2) using Organic Acids Catur Rini Widyastuti; Artanti Estiningtyas; Indah Cahyani Puspitaningrum; Siti Ajeng Muslimah; Shafa Noviandrea Towidjojo; Danang Subarkah Hadikawuryan; Rizki Setiadi; Aryo Baskoro Utomo; Muhammad Olvianas
Rekayasa Vol. 23 No. 2 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i2.40853

Abstract

The increasing use of portable electronic devices has led to an increase in lithium-ion battery (LiB) waste, which contains hazardous metals such as cobalt. It is noteworthy that cobalt accounts for up to 30% of the battery weight, significantly higher than its concentration in natural ores (<1%). Conventional recovery methods use strong inorganic acids (e.g., H₂SO₄, HCl), which are effective but produce hazardous wastewater and require complex treatment procedures. In this study, the cobalt extraction process was carried out using a hydrometallurgical method using organic acids, specifically ascorbic acid and citric acid. The extraction process was carried out with variations in organic acid concentrations ranging from 0.5 M to 2.5 M at temperatures of 55°C and 70°C. The extracted liquid was collected and analyzed for cobalt content using an Atomic Absorption Spectrophotometer (AAS). The cobalt leaching process using citric acid successfully dissolved 13.58–13.89 mg/L of cobalt. Meanwhile, from the leaching process with ascorbic acid, dissolved cobalt was obtained in the range of 10.96–12.87 mg/L. Based on the data obtained from the leaching process using organic acids, it can be seen that the best leaching process was obtained with citric acid at a concentration of 0.5 M at a temperature of 55°C, which produced 13,837 mg/L of dissolved cobalt. The extracted cobalt can be used for the synthesis of cobalt acetate, which is a fine chemical. However, not all cobalt dissolved in the leaching process can be precipitated to produce cobalt acetate. Of all the leaching solutions with both organic acids at different concentrations, only the solution from the leaching process with ascorbic acid at a concentration of 0.5 M was successfully precipitated and further synthesized into cobalt acetate with a yield of 17.42 wt%. In addition, FTIR analysis confirmed that the synthesized cobalt acetate was consistent with the reference cobalt(II) acetate tetrahydrate, with the difference in intensity indicating lower hydration in the synthesized sample.
Comparison of Nanoemulsions and Conservation as a Biopesticide Encapsulation Strategy from Fermentation and Extraction: Review Astrilia Damayanti; Widya Sari Kusuma Wijayanti; Grandis Belva Ardana; Fera Utnita Sari; Muhamad Reihan Prananda; Sangeetaprivya P. Siva
Rekayasa Vol. 23 No. 2 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i2.42739

Abstract

The increasing demand for sustainable agriculture has accelerated the development of biopesticides as environmentally friendly alternatives to synthetic pesticides. However, their application remains constrained by poor stability, low solubility, rapid degradation, and inconsistent field performance. This review aims to evaluate the relationship between bioactive compound production methods and appropriate encapsulation techniques, focusing on fermentation- and extraction-derived biopesticides. A comparative analysis of recent literature was conducted to assess the compatibility of fermentation and extraction processes with coacervation and nanoemulsion encapsulation technologies. The analysis shows that fermentation-derived bioactive compounds, including microbial spores and protein toxins, are best protected through coacervation, which enhances environmental stability and enables controlled release. Conversely, extraction-derived bioactive compounds, such as essential oils, terpenoids, and phenolics, are more effectively formulated using nanoemulsions, improving solubility, dispersion, bioavailability, and biological efficacy while reducing application rates. Matching bioactive production methods with suitable encapsulation strategies significantly enhances formulation stability, active ingredient delivery, and pest control performance. This integrated approach provides a practical framework for developing effective, stable, and commercially viable biopesticides to support sustainable agricultural systems. This review, based on a comparative analysis of recent studies, highlights that fermentation-derived bioactives are more compatible with coacervation systems, whereas extraction-derived bioactives are better suited for nanoemulsion formulations. The findings emphasise that aligning the characteristics of bioactive sources with suitable encapsulation techniques is crucial for improving stability, active ingredient loading, and pest control performance. This integrated approach provides a strategic framework for designing effective, stable, and commercially viable biopesticide formulations that support sustainable agriculture.
Conductive Smart Scaffold for Electrochemical Sensing in Bone Tissue Engineering Applications: A Review Rusyda Fajarani; Siti Fauziyah Rahman; Armelia Ramandha
Rekayasa Vol. 24 No. 1 (2026)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v24i1.43191

Abstract

Tissue engineering technology using biomaterial-based scaffolds has been developed to support and regulate cellular activities, including cell adhesion, proliferation, migration, and the differentiation of electrically excitable cells through the incorporation of conductive materials. Conductive smart scaffolds have emerged as a promising platform for bone tissue engineering by integrating structural support with electrochemical sensing capabilities. Recent advances have enabled the development of conductive scaffolds integrated with electrochemical sensing systems for real-time, non-invasive monitoring of cellular behavior during bone regeneration. This review analyzes recent developments in electroactive conductive scaffolds and scaffold-based electrochemical sensing platforms for bone tissue engineering applications. A comprehensive literature review was conducted across major scientific databases to identify studies related to scaffold composition, conductive materials, electrochemical characterization methods, sensing strategies, and associated biological responses. The reviewed studies demonstrate that conductive polymers and carbon-based nanomaterials are widely used to enhance scaffold electroactivity and osteogenic performance. Electrochemical characterization techniques, including Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), are commonly employed to evaluate scaffold conductivity, redox behavior, and electrochemical stability. Furthermore, conductive scaffold-based electrochemical sensing systems have been successfully applied to monitor cell viability, adhesion, proliferation, mineralization, and osteogenic differentiation in a label-free, non-destructive manner. The integration of conductive biomaterials with electrochemical sensing platforms enables precise monitoring of cellular activities through changes in electrical signals, impedance, and electrochemical responses. Overall, conductive smart scaffolds represent a promising multifunctional strategy for advancing bone tissue engineering by combining biocompatibility, electroactivity, regenerative capability, and real-time biosensing within a single scaffold system.
Effect of Ultrasonic Processing on Mechanical and Surface Properties of Chitosan-Alginate-Starch Edible Films Desi Rahmawati; Azafilmi Hakiim; Indah Cintami; Alehandro Sitinjak
Rekayasa Vol. 23 No. 2 (2025)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v23i2.49226

Abstract

Marine plastic waste has driven the development of biodegradable packaging alternatives such as edible films. However, their mechanical strength and structural homogeneity remain challenging. This study investigates the effect of ultrasonic processing on the mechanical and surface properties of edible films based on chitosan–alginate–starch blends. Edible films were prepared with various polysaccharide combinations and subjected to ultrasonic treatment during processing. The sample was treated with ultrasonic waves at a frequency of 37 kHz and a temperature of 30 °C for 3 minutes. The results show that ultrasonic treatment improved surface homogeneity, as indicated by smoother structures and reduced bubble formation compared to non-ultrasonic films. In terms of mechanical properties, ultrasonic treatment exhibited varying effects on tensile strength but consistently increased elongation at break, indicating enhanced flexibility. The highest tensile strength was observed in chitosan-based films (45.479 MPa), while the highest elongation (41%) was achieved in chitosan–alginate films under ultrasonic treatment. The ternary blend (chitosan–alginate–starch) demonstrated balanced mechanical properties in both ultrasonic and non-ultrasonic conditions. Chemical analysis using FTIR spectroscopy showed that ultrasonic treatment affected intermolecular interactions within the film matrix, as indicated by shifts and changes in the intensity of absorption bands in several functional groups. These findings suggest that ultrasonic processing plays a crucial role in improving film structure and flexibility, while the polysaccharide composition governs the balance between strength and elasticity.

Page 4 of 4 | Total Record : 35

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