Degradation Study of Thin-Film Silicon Structures in a Cell Culture Medium

Abstract

Thin-film silicon (Si)-based transient electronics represents an emerging technology that enables spontaneous dissolution, absorption and, finally, physical disappearance in a controlled manner under physiological conditions, and has attracted increasing attention in pertinent clinical applications such as biomedical implants for on-body sensing, disease diagnostics, and therapeutics. The degradation behavior of thin-film Si materials and devices is critically dependent on the device structure as well as the environment. In this work, we experimentally investigated the dissolution of planar Si thin films and micropatterned Si pillar arrays in a cell culture medium, and systematically analyzed the evolution of their topographical, physical, and chemical properties during the hydrolysis. We discovered that the cell culture medium significantly accelerates the degradation process, and Si pillar arrays present more prominent degradation effects by creating rougher surfaces, complicating surface states, and decreasing the electrochemical impedance. Additionally, the dissolution process leads to greatly reduced mechanical strength. Finally, in vitro cell culture studies demonstrate desirable biocompatibility of corroded Si pillars. The results provide a guideline for the use of thin-film Si materials and devices as transient implants in biomedicine.

A 3D biomimetic optoelectronic scaffold repairs cranial defects

“…For biomedical applications such as tissue regeneration, desirable implants should operate effectively throughout a certain period of time before they are fully absorbed in the biological environment. It is known that crystalline Si films naturally dissolve in the biological environment at a rate of 10 to 100 nm/day ( 43 , 44 ), which would also cause the gradual degradation of their optoelectronic performance. We study degradation behaviors of Si films immersed in standard cell culture media at 37°C ( Fig.…”

Controlling the lifetime of biodegradable electronics: from dissolution kinetics to trigger acceleration

“…However, biodegradable devices within the body need to exhibit the characteristic of stable operation for a certain period, followed by degrading at a proper moment [40] . In pursuit of controlling the dissolution rate of silicon and achieving on-demand degradation, studies involving the application of external energy to Si NMs have been conducted [46,[62][63][64] . These investigations broadly encompass two main directions, with the following fundamental mechanisms: photo-assisted etching [41] and the augmentation of surface area by inducing microcrack [46,[62][63][64] .…”

“…In pursuit of controlling the dissolution rate of silicon and achieving on-demand degradation, studies involving the application of external energy to Si NMs have been conducted [46,[62][63][64] . These investigations broadly encompass two main directions, with the following fundamental mechanisms: photo-assisted etching [41] and the augmentation of surface area by inducing microcrack [46,[62][63][64] . The former draws inspiration from using lasers in etching to induce band bending in semiconducting materials [59] .…”

“…While significant changes in dissolution rate were not observed, considering the low levels of illumination compared to typical photo-assisted etching [65] , it suggested the potential of using light exposure [41] . The latter approach involves generating microcracks through thermal expansion or lithiation of substrates, causing deformation stress in silicon and resulting in rapid dissolution [46,[62][63][64] . Microcracks serve to increase surface area of silicon, thereby augmenting the number of reaction sites.…”

“…Reproduced with permission [41] , Copyright 2014, American Chemical Society; (H) Process of microcrack generation in Si circuit through lithiation. Reproduced with permission [46] , Copyright 2023, John Wiley and Sons. HBSS: Hank's balanced salt solution; Si NMs: silicon nanomembranes.…”