Natural Wax for Transient Electronics

Abstract

Emerging classes of bioresorbable electronic materials serve as the basis for active biomedical implants that are capable of providing sensing, monitoring, stimulating, and other forms of function over an operating period matched to biological processes such as wound healing. These platforms are of interest because subsequent dissolution, enzymatic degradation, and/ or bioresorption can eliminate the need for surgical extraction. This report introduces natural wax materials as long-lived, hydrophobic encapsulation layers for such systems, where biodegradation eventually occurs by chain scission. Studies of wax stability as an encapsulation material demonstrate the ability to retain operation of underlying biodegradable electronic systems for durations between a few days to a few weeks during complete immersion in aqueous solutions in ex-vivo physiological conditions. Electrically conductive composites result from the addition of tungsten micro/nanoparticles, as a conductive, printable paste with similar lifetimes. Demonstrations of these materials in partially biodegradable wireless light-emitting diodes and nearfield communication circuits illustrate their use in functional bioresorbable electronic systems. Investigations in animal models reveal no signs of toxicity or other adverse biological responses.

Materials, Mechanics Designs, and Bioresorbable Multisensor Platforms for Pressure Monitoring in the Intracranial Space

“…Beeswax (CB01) and Candelilla wax (CB10) are two natural materials reported recently for applications in bioresorbable electronics. [ 33 ] Beeswax contains hydrocarbons (14%), monoesters (35%), diesters (14%), triesters (3%), hydroxy monoesters (4%), hydroxy polyesters (8%), acid esters (1%), acid polyesters (2%), free fatty acids (12%), free fatty alcohols (1%), unidentified constituents (6%). [ 34 ] Candelilla wax includes hydrocarbons (about 50%, chains with 29–33 carbons), esters of higher molecular weight (20–29%), free acids (7–9%), and resins (12–14%, mainly triterpenoid esters).…”

“…Hydrolysis of ester and anhydride derivatives in these biocompatible and bioresorbable materials leads to dissolution on timescales of several months in vivo, as described in previous publications. [ 33,36 ] The swelling ratio of natural wax increases with the amount of these derivatives. The water uptake in Beeswax tends to be larger than that in Candelilla wax.…”

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

“…All the discussed metals were deposited via vacuum‐based technologies, such as, chemical vapor deposition and sputtering. However, a huge interest is nowadays directed toward the development of new and low‐cost methods to reliably fabricate bioresorbable metal films, such as laser printing and metal nanoparticle‐filled conductive inks …”

“…Won et al reported on the use of natural waxes as materials for long‐time and hydrophobic encapsulation in bio/ecoresorbable electronics. Soy, myrtle, and candelilla waxes, derived from soybeans (via soybean oil), myrica cerifera (myrtle), and candelilla shrubs, respectively, were tested.…”

Thermoresponsive Transient Radio Frequency Antennas: Toward Triggered Wireless Transient Circuits

“…While silk has gained extensive popularity as a device substrate material in various transient systems, it is noted that the swelling of silk represents a long‐standing issue that can result in unwanted delamination prior to achieving the desired performance . Though hydrophobic above the LCST, a similar issue occurs when dealing with MC substrates in warm water.…”