Advanced Materials and Devices for Bioresorbable Electronics

Abstract

Recent advances in materials chemistry establish the foundations for unusual classes of electronic systems, characterized by their ability to fully or partially dissolve, disintegrate, or otherwise physically or chemically decompose in a controlled fashion after some defined period of stable operation. Such types of "transient" technologies may enable consumer gadgets that minimize waste streams associated with disposal, implantable sensors that disappear harmlessly in the body, and hardware-secure platforms that prevent unwanted recovery of sensitive data. This second area of opportunity, sometimes referred to as bioresorbable electronics, is of particular interest due to its ability to provide diagnostic or therapeutic function in a manner that can enhance or monitor transient biological processes, such as wound healing, while bypassing risks associated with extended device load on the body or with secondary surgical procedures for removal. Early chemistry research established sets of bioresorbable materials for substrates, encapsulation layers, and dielectrics, along with several options in organic and bio-organic semiconductors. The subsequent realization that nanoscale forms of device-grade monocrystalline silicon, such as silicon nanomembranes (m-Si NMs, or Si NMs) undergo hydrolysis in biofluids to yield biocompatible byproducts over biologically relevant time scales advanced the field by providing immediate routes to high performance operation and versatile, sophisticated levels of function. When combined with bioresorbable conductors, dielectrics, substrates, and encapsulation layers, Si NMs provide the basis for a broad, general class of bioresorbable electronics. Other properties of Si, such as its piezoresistivity and photovoltaic properties, allow other types of bioresorbable devices such as solar cells, strain gauges, pH sensors, and photodetectors. The most advanced bioresorbable devices now exist as complete systems with successful demonstrations of clinically relevant modes of operation in animal models. This Account highlights the foundational materials concepts for this area of technology, starting with the dissolution chemistry and reaction kinetics associated with hydrolysis of Si NMs as a function of temperature, pH, and ion and protein concentration. A following discussion focuses on key supporting materials, including a range of dielectrics, metals, and substrates. As comparatively low performance alternatives to Si NMs, bioresorbable organic semiconductors are also presented, where interest derives from their intrinsic flexibility, low-temperature processability, and ease of chemical modification. Representative examples of encapsulation materials and strategies in passive and active control of device lifetime are then discussed, with various device illustrations. A final section outlines bioresorbable electronics for sensing of various biophysical parameters, monitoring electrophysiological activity, and delivering drugs in a programmed manner. Fundamental research in chemistry remains e...

E-Skin: From Humanoids to Humans [Point of View]

“…in real-time [7,8] For health and medical applications there are additional requirements such as substrates should be disposable, dissolvable, bioresorbable and biocompatible etc. [9,10]. Such eskin patches could either be placed directly on body surface or on daily wearables such as clothes, watch or jewellery etc.…”

Bioresorbable Materials on the Rise: From Electronic Components and Physical Sensors to In Vivo Monitoring Systems

“…[33] The authors investigated the dissolution rate of Si NMs (B-doped, 10 15 cm −3 , 200 nm thick) in PBS (1×) spiked with different concentrations of albumin (0.01-35 g L −1 ), Si(OH) 4 (0-300 mg L −1 ) and cations (Na + , Mg 2+ and Ca 2+ , 1 × 10 −3 m) at 37 °C. The increase of the protein concentration slowed down the dissolution rate due to augmented protein adsorption onto the NM surface; moreover, regardless of the concentration (and presence) of proteins, the dissolution rate reduced by increasing the concentration of Si(OH) 4 , consistently with the chemical equilibrium reported in Equation (1). Conversely, the presence of cations in the aqueous medium (i.e., PBS at pH 7.4, with 35 g L −1 of proteins at 37 °C) led to an accelerated dissolution rate, which was greater for divalent cations (namely, Ca 2+ and Mg 2+ ) with respect to monovalent cations (Na + ).…”

“…and 2) hydrolysis of silicon oxide, according to Equation (4). The overall reaction is reported in Equation (6)…”

“…Traditional medical devices designed to be implanted in the human body to treat either acute or chronic diseases (e.g., cardiac pacemakers, cochlear implants, coronary stents, articular prostheses) are made of (or coated with) inert biocompatible materials and optimized to warrant the organ functionality from days to years, depending of the targeted problem/disease, before surgical retrieval/replacement (when needed) . While for some specific cases (e.g., heart stimulation, hearing loss, coronary heart disease) implanted devices ideally working/operating over the whole patient life are required, in many other cases (e.g., muscle stimulation, bone growth stimulation, neuro stimulation, wound healing) the devices are required to work/operate only for a prescribed amount of time, so that surgical retrieval is eventually needed, which could be potentially dangerous for patient health …”

Bioinspired Prosthetic Interfaces

“…However, due to the mechanical incompliance and the possibility of toxicity of inorganic materials, biodegradable polymers based on naturally derived poly mers and synthetic polymers became the field of intensive study. [135,136] In a recent review reported by Feig et al, taking an example of a typical transistor structure, it provided thorough materials design considerations for the individual degradable components, including but not limited to electrodes (e.g., corrodible metals such as Fe and Mg), substrates (e.g., polylactic-co-glycolic acid (PLGA)), dielectrics (e.g., poly(glycerol sebacate) (PGS)) and semiconductor films. [137] With the wide choices of materials to achieve degradability, research on transient wearable and skin-like electronics are expected to burgeon.…”