Devices constructed using bioresorbable materials have many roles in clinical medicine, ranging from drug delivery vehicles [1, 2] to stents [3, 4] and sutures.[5, 6] In such cases, the function is defined primarily by the mechanics and/or the structure of the component, with operation that is often passive. The ability to achieve similar bioresorbable characteristics in active semiconductor devices and sensors could significantly expand the possible modes of use. Past approaches include partially resorbable systems based on miniaturized silicon transistors bonded to biomaterial substrates and, in separate work, on organic active materials (eg semiconductors).[7–11] Recent studies demonstrate a completely water soluble class of silicon-based technology,[12] to enable devices and systems that build on foundational knowledge and engineering capabilities derived from the integrated circuit industry. Components of this type can be implanted into the human body where they gradually dissolve into biofluids after their useful functional life, thereby eliminating unnecessary device load without the need for surgical extraction. For many applications, radio frequency (RF) operation is a key feature, both for data transmission and for power supply. The results presented here represent progress in this direction. We report antennas, rectifying diodes, transistors, capacitors, inductors, resistors, ring oscillators and RF energy harvesting sub-systems, all of which involve water soluble and biocompatible constituent materials, ie silicon nanomembranes (Si NMs; semiconductors), magnesium (Mg; conductors), silicon dioxide or magnesium oxide (low temperature SiO 2 or MgO; interlayer dielectrics), and silk (substrates). One of the most critical, but simplest, elements in RF systems for wireless reception/transmission is in the antenna. Transient antennas can be formed by evaporation of Mg (500 nm) through stencil masks made of polyimide (PI) films (Kapton, 12.5 μm, Dupont, USA) on thin films of silk. Two designs form the focus of studies reported here: simple linear dipoles consisting of two quarter wavelength arms and wideband quasi log-periodic dipoles, designed to operate at∼ 2.4 GHz and∼ 950 MHz, respectively. Figure 1a presents images of a transient Mg antenna at a sequence of times during immersion in deionized (DI) water at room temperature. The Mg and silk completely disappear after∼ 2 hours by hydrolysis and simple dissolution, respectively. An alternative route to similar antennas, but with thicknesses that can be much larger than the skin depth at relevant RF frequencies, exploits Mg foils (thickness from 5 μm to 50 μm, purity of 99.9%, Goodfellow, UK) cut into appropriate shapes. A layer of solvent-perfused silk serves as an adhesive to bond such antennas to silk substrates (Figure S1a). The measured S-parameters in Figure 1 b show that both antennas are well matched to their designed operating frequencies. Images of the devices with coaxial connectors appear in Figure S2. Figure S1b shows a 950 MHz antenna integrated with a commercial RF power scavenging system on a printed circuit board to demonstrate functionality. Additional details can be found in Figure S1c. Various transient devices with passive RF function, such as capacitors, inductors, and resistors, are also essential. Figure 1, c to g, provides images and electrical properties of several such components. As an example, a simple transient resistor consisting of a serpentine trace of Mg (Figure 1 c) formed by evaporation onto silk through a stencil mask, indicates a resistance of 100 ohm, suitable for use in RF currentlimiters and voltage dividers. Capacitors and inductors can be formed on …