Personalized antimicrobial and soundproof earplugs through embedded-suspension 3D printing of polydimethylsiloxane-Ag composites for the prevention of swimmers' otitis externa

Abstract

Aquatic activities, particularly swimming, have been demonstrated to enhance physical conditioning and psychological well-being. However, the risk of water-induced otitis externa—caused by microbial colonization in the external auditory canal—often deters sustained participation in aquatic sports. Traditional swimming earplugs are typically limited in terms of comfort, water resistance, and antimicrobial protection, which can lead to potential ear canal infections and reduced effectiveness in preventing water ingress. In this study, we proposed using 3D scanning and printing technology to produce personally customized swimming earplugs to address these challenges. Embedded-suspension 3D printing technology was applied to fabricate structures using non-self-supporting Polydimethylsiloxane (PDMS) ink, printing hydrophobic ink in a hydrophilic system. The 3D-printed PDMS/Ag-3% composites exhibited an excellent inhibition rate (99.89%), good sound insulation performance (>30 dB, 1000–6300 Hz, 8 mm thickness), elasticity (elongation at break of 62.93%), and low modulus (0.85 MPa). We then recruited 60 beginner swimmers for a wear trial to demonstrate the effectiveness of personalized earplugs in preventing otitis externa and reducing ear canal irritation. This approach not only highlights the potential of 3D printing technology in sports equipment but also offers new insights for developing customized wearables.

Keywords

3D printing / Swimming earplugs / Swimmer’s ear prevention / Sports equipment / Sports injury prevention

Funding

This work was supported in part by the Open Project of Anhui Engineering Research Center for Neural Regeneration Technology and Medical New Materials (AHNR2024Z002).

Conflict of Interest

The authors declare that they have no competing interests.

References

[1] DeFlorio-Barker S, Wing C, Jones RM, Dorevitch S. Estimate of incidence and cost of recreational waterborne illness on United States surface waters. Environ Health. 2018;17(1):3. doi: 10.1186/s12940-017-0347-9

[2] Lipska J, Hamerska J, Hamerska L, et al. Swimmer’s ear: Prevention, diagnosis, treatment, and management strategies for athletes. Qual Sport. 2024;18:53330. doi: 10.12775/QS.2024.18.53330

[3] Perez-Stable EJ, Sayre MH. Reducing health disparities to promote health equity through policy research. Ethn Dis. 2019;29(S2):321-322. doi: 10.18865/ed.29.S2.321

[4] Caramia G, Serafini V, Loggi A. The swimmer’s otitis. An up to date and prevention options. Pediatr Med Chir. 2013;35(3):177-182. doi: 10.4081/pmc.2013.38

[5] Strauss MB, Dierker RL. Otitis externa associated with aquatic activities (swimmer’s ear). Clin Dermatol. 1987;5(3):103-111. doi: 10.1016/S0738-081X(87)80016-0

[6] Beers SL, Abramo TJ. Otitis externa review. Pediatr Emerg Care. 2004;20(4):250-256. doi: 10.1097/01.pec.0000121246.99242.f5

[7] Wang MC, Liu CY, Shiao AS, Wang T. Ear problems in swimmers. J Chin Med Assoc. 2005;68(7):347-352. doi: 10.1016/S1726-4901(09)70174-1

[8] Kanagamuthu P, Dhanasekaran B, Karthika SR, Raghavan VK. To determine the pH of external auditory canal in otitis externa: A prospective observational study in a tertiary health care centre. Indian J Otolaryngol Head Neck Surg. 2023;75(1):502-506. doi: 10.1007/s12070-023-03591-x

[9] Ellis J, De La Lis A, Rosen E, Simpson MTW, Beyea MM, Beyea JA. Approach to otitis externa. Can Fam Physician. 70(6):617-623. doi: 10.46747/cfp.7010617

[10] World Health Organization. Precision Public Health Strategy. Brazzaville: WHO African Region; 2025. p. 2024-2030.

[11] Wade TJ, Sams EA, Beach MJ, Collier SA, Dufour AP. The incidence and health burden of earaches attributable to recreational swimming in natural waters: A prospective cohort study. Environ Health. 2013;12(1):67. doi: 10.1186/1476-069X-12-67

[12] Kumpel E, Delaire C, Peletz R, et al. Measuring the impacts of water safety plans in the Asia-Pacific region. Int J Environ Res Public Health. 2018;15(6):1223. doi: 10.3390/ijerph15061223

[13] Bhatia R, Chauhan A, Rana M, Kaur K, Pradhan P, Singh M. Economic burden of otitis media globally and an overview of the current scenario to alleviate the disease burden: A systematic review. Int Arch Otorhinolaryngol. 2024;28(3):e552-e558. doi: 10.1055/s-0043-1767802

[14] Graydon K, Waterworth C, Miller H, Gunasekera H. Global burden of hearing impairment and ear disease. J Laryngol Otol. 2019;133(1):18-25. doi: 10.1017/S0022215118001275

[15] Mahboubi H, Lee A, Kiumehr S, Zardouz S, Shahriari S, Djalilian HR. Efficacy of commercial earplugs in preventing water intrusion during swimming. Otolaryngol Head Neck Surg. 2013;148(3):415-419. doi: 10.1177/0194599812471798

[16] Chisholm EJ, Kuchai R, McPartlin D. An objective evaluation of the waterproofing qualities, ease of insertion and comfort of commonly available earplugs. Clin Otolaryngol Allied Sci. 2004;29(2):128-132. doi: 10.1111/j.1365-2273.2004.00795.x

[17] Yang J, Lu J, Han D, Zhou B, Du A. Direct ink writing of aerogels: Fundamentals, strategies, applications, and perspectives. Prog Mater Sci. 2025;152:101462. doi: 10.1016/j.pmatsci.2025.101462

[18] Yang J, Lu J, Xi S, et al. Direct 3D print polyimide aerogels for synergy management of thermal insulation, gas permeability and light absorption. J Mater Chem A Mater Energy Sustain. 2023;11(39):13. doi: 10.1039/D3TA02928J

[19] Han D, Yang J, Wang H, et al. 3D-printed hybrid zirconia hydrogels for ultrahigh-efficiency phosphate adsorption. Adv Compos Hybrid Mater. 2024;7(4):1-14. doi: 10.1007/s42114-024-00941-3

[20] Saadi M, Maguire A, Pottackal NT, et al. Direct ink writing: A 3D printing technology for diverse materials. Adv Mater. 2022;34(3):e2108855. doi: 10.1002/adma.202108855

[21] Walker DA, Hedrick JL, Mirkin CA. Rapid, large-volume, thermally controlled 3D printing using a mobile liquid interface. Science. 2019;366(6463):360-364. doi: 10.1126/science.aax1562

[22] Wu Q, Song K, Zhang D, et al. Embedded extrusion printing in yield-stress-fluid baths. Matter. 2022;5(11):3775-3806. doi: 10.1016/j.matt.2022.09.003

[23] Yang J, Qian X, Yang J, et al. Additive-free aerogel 3D printing using ultra-low storage modulus inks. Adv Funct Mater. 2024:2423739. doi: 10.1002/adfm.202423739

[24] McCormack A, Highley CB, Leslie NR, Melchels FPW. 3D printing in suspension baths: Keeping the promises of bioprinting afloat. Trends Biotechnol. 2020;38(6):584-593. doi: 10.1016/j.tibtech.2019.12.020

[25] Lee A, Hudson AR, Shiwarski DJ, et al. 3D bioprinting of collagen to rebuild components of the human heart. Science. 2019;365(6452):482-487. doi: 10.1126/science.aav9051

[26] Croom BP, Abbott A, Kemp JW, et al. Mechanics of nozzle clogging during direct ink writing of fiber-reinforced composites. Addit Manuf. 2021;37:101701. doi: 10.1016/j.addma.2020.101701

[27] Altıparmak SC, Yardley VA, Shi Z, Lin J. Extrusion-based additive manufacturing technologies: State of the art and future perspectives. J Manuf Process. 2022;83:607-636. doi: 10.1016/j.jmapro.2022.09.032

[28] Billiet T, Gevaert E, De Schryver T, Cornelissen M, Dubruel P. The 3D printing of gelatin methacrylamide cell-laden tissue-engineered constructs with high cell viability. Biomaterials. 2014;35(1):49-62. doi: 10.1016/j.biomaterials.2013.09.078

[29] Nathan A, Ahnood A, Cole M, et al. Flexible electronics: The next ubiquitous platform. Proc IEEE. 2012;100(SI):1486-1517. doi: 10.1109/JPROC.2012.2190168

[30] Gondil VS, Ashcraft M, Ghalei S, et al. Anti-infective bacteriophage immobilized nitric oxide-releasing surface for prevention of thrombosis and device-associated infections. ACS Appl Bio Mater. 2025;8(3):1362-1376. doi: 10.1021/acsabm.4c01638

[31] Wolf MP, Salieb-Beugelaar GB, Hunziker P. PDMS with designer functionalities-properties, modifications strategies, and applications. Prog Polym Sci. 2018;83:97-134. doi: 10.1016/j.progpolymsci.2018.06.001

[32] Duraivel S, Laurent D, Rajon DA, et al. A silicone-based support material eliminates interfacial instabilities in 3D silicone printing. Science. 2023;379(6638):1248-1252. doi: 10.1126/science.ade4441

[33] O’Bryan CS, Bhattacharjee T, Hart S, et al. Self-assembled micro-organogels for 3D printing silicone structures. Sci Adv. 2017;3(5):e1602800. doi: 10.1126/sciadv.1602800

[34] Hinton TJ, Hudson A, Pusch K, Lee A, Feinberg AW. 3D printing PDMS elastomer in a hydrophilic support bath via freeform reversible embedding. ACS Biomater Sci Eng. 2016;2(10):1781-1786. doi: 10.1021/acsbiomaterials.6b00170

[35] Fenny Indah S, Desy N, Dina F. Overview: Application of Carbopol 940 in Gel. In: Proceedings of the International Conference on Health and Medical Sciences (AHMS 2020). Netherlands: Atlantis Press; 2021. p. 80-4.

[36] Prasad SR, Teli SB, Ghosh J, et al. A review on bio-inspired synthesis of silver nanoparticles: Their antimicrobial efficacy and toxicity. Eng Sci. 2021;16:90-128. doi: 10.30919/es8d479

[37] Bhattacharjee T, Zehnder SM, Rowe KG, et al. Writing in the granular gel medium. Sci Adv. 2015;1(8):e1500655. doi: 10.1126/sciadv.1500655

[38] Mo F, Zhou Q, He Y. Nano-Ag: Environmental applications and perspectives. Sci Total Environ. 2022;829:154644. doi: 10.1016/j.scitotenv.2022.154644

[39] Yin IX, Zhang J, Zhao IS, Mei ML, Li Q, Chu CH. The antibacterial mechanism of silver nanoparticles and its application in dentistry. Int J Nanomedicine. 2020;15:2555-2562. doi: 10.2147/IJN.S246764

[40] Xie Y, Zhou B, Du A. Slow-sound propagation in aerogel-inspired hybrid structure with backbone and dangling branch. Adv Compos Hybrid Mater. 2021;4(8):248-256. doi: 10.1007/s42114-021-00234-z

[41] Borah B, Dash RK. Improved dielectric properties of rGO/ PDMS composites by incorporation of Ag nanoparticles. J Mater Sci Mater Electron. 2022;33(15):12334-12350. doi: 10.1007/s10854-022-08191-z

[42] Centers for Disease Control and Prevention Preventing Swimming-Related Illnesses; 2025. Available from: https://www.cdc.gov/healthy-swimming/prevention/index.html [Last accessed on 2024 Jul 20.

[43] Mullins L. Softening of rubber by deformation. Rubber Chem Technol. 2012;42(1):339-362. doi: 10.5254/1.3539210

[44] Keating P, Kuo G. Comparison of speaking fundamental frequency in English and Mandarin. J Acoust Soc Am. 2012;132(2):1050. doi: 10.1121/1.4730893

[45] Vlassov S, Oras S, Timusk M, et al. Thermal, mechanical, and acoustic properties of polydimethylsiloxane filled with hollow glass microspheres. Materials (Basel). 2022;15(5):1652. doi: 10.3390/ma15051652

[46] Xia Z, Wu X, Yang Q, et al. Analysis and test of sound insulation performance of multilayer structures. Noise Vibr Control. 2023;43:129-34. doi: 10.3969/j.issn.1006-1355.2023.06.020

[47] Vortice. Air Handling Unit Catalog. Vortice. Available from: https://www.vortice.com/media2/export/inglese/doc_pubblicita_catalog_air_handling_unit_122215.pdf [Last accessed on 2020 Jun 27].

[48] Xu Y, De la Paz E, Paul A, et al. In-ear integrated sensor array for the continuous monitoring of brain activity and of lactate in sweat. Nat Biomed Eng. 2023;7(10):1307-1320. doi: 10.1038/s41551-023-01095-1

[49] Burgos CP, Gärtner L, Ballester MAG, et al. In-ear accelerometer-based sensor for gait classification. IEEE Sens J. 2020;20(21):12895-12902. doi: 10.1109/jsen.2020.3002589