medical devices (IMDs) and transient electronic devices, which can be later dissolved in a controlled manner. In current medical practice, IMDs are used during life-or-death cases only due to a secondary follow-up IMD retrieval surgery requirement which is an additional risk and an economic burden to the patient, doctor, and the government. Biodegradable sensors are expected to enable unprecedented solutions for diagnostic, telemetry, and therapeutic IMDs without secondary IMD retrieval surgery. [4][5][6][7] On the other hand, the increasing number of single-use electronics deepens the electronic waste (e-waste) problem, which is estimated to reach 74 million tons by 2030. [8] Therefore, eco-friendly alternatives such as transient electronics that easily degrade into disposable byproducts are expected to play a vital role in alleviating environmental concerns and increasing the abundance of wearable medical devices. [8][9][10] In addition to biodegradability, miniaturization, flexibility, and stretchability are critical factors that determine the range of applications in medicine and electronics. Microfabrication of flexible and stretchable sensors that occupy a minimal footprint, conformally adhere to host tissue while retaining their electrical features during mechanical loading, and dissolve within bodily fluids are highly desirable for next-generation IMDs and sustainable wearable electronics. [11][12][13][14] Toward this end, none of the recently reported Biodegradable sensors based on integrating conductive layers with polymeric materials in flexible and stretchable forms have been established. However, the lack of a generalized microfabrication method results in large-sized, low spatial density, and low device yield compared to the silicon-based devices manufactured via batch-compatible microfabrication processes. Here, a batch fabrication-compatible photolithography-based microfabrication approach for biodegradable and highly miniaturized essential sensor components is presented on flexible and stretchable substrates. Up to 1600 devices are fabricated within a 1 cm 2 footprint and then the functionality of various biodegradable passive electrical components, mechanical sensors, and chemical sensors is demonstrated on flexible and stretchable substrates. The results are highly repeatable and consistent, proving the proposed method's high device yield and high-density potential. This simple, innovative, and robust fabrication recipe allows complete freedom over the applicability of various biodegradable materials with different properties toward the unique application of interests. The process offers a route to utilize standard micro-fabrication procedures toward scalable fabrication of highly miniaturized flexible and stretchable transient sensors and electronics.

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Microfabrication of Biodegradable Sensors In article number 2207081, Levent Beker and co‐workers report a photolithography‐based microfabrication process for bioresorbable devices. Consecutive application of sacrificial, adhesion and protection layers enable the use of delicate conductive and insulating bioresorbable materials through standard microfabrication processes. Using this approach, high‐density passive electric components and chemical sensors critical for transient electronics and implant applications are developed.

Smart contact lenses (SCLs) have drawn substantial interest for continuous health monitoring applications. Even though most of the reported works utilize near‐field communication (NFC) or inductive coupling for wireless powering and data transmission, developing a scalable and rapid fabrication technique for annular ring antennas confined in a small contact lens area is still an unsolved challenge. Here, femtosecond laser ablation is employed for the first time as a simple, single‐step, and highly precise fabrication technique for NFC antennas using conventional flexible printed circuit board materials. Antenna lines with depth and width of 9 and 35 μm are achieved, respectively. The antenna with a footprint of 19.5 mm2 is characterized in biological solution followed by aging, and bending tests, and a frequency deviation of less than %1 is recorded. A real‐life application is demonstrated by fabricating an SCL embedded with the antenna, an NFC chip, and an electrochemical sensor for wireless monitoring of glucose in artificial tear solution by a smartphone. The device could successfully quantify biologically relevant glucose concentrations ranging from 0.2 to 1 mM with a limit‐of‐detection of 66 μM. In addition, device response to interfering molecules is less than ±1 nA, and the spike‐and‐recovery test is successfully demonstrated.

Soft, skin-mounted microfluidic devices can collect microliter volumes of eccrine sweat and are capable of in-situ real-time analysis of different biomarkers to assess physiological state and health. Chrono-analysis of sweat...