Biodegradable transient devices represent an emerging type of electronics that could play an essential role in medical therapeutic/diagnostic processes, such as wound healing and tissue regeneration. The associated biodegradable power sources, however, remain as a major challenge toward future clinical applications, as the demonstrated electrical stimulation and sensing functions are limited by wired external power or wireless energy harvesters via near-field coupling. Here, materials' strategies and fabrication schemes that enable a high-performance fully biodegradable magnesium-molybdenum trioxide battery as an alternative approach for an in vivo on-board power supply are reported. The battery can deliver a stable high output voltage as well as prolonged lifetime that could satisfy requirements of representative implantable electronics. The battery is fully biodegradable and demonstrates desirable biocompatibility. The battery system provides a promising solution to advanced energy harvesters for self-powered transient bioresorbable implants as well as eco-friendly electronics.

Carcinoma of the ampulla of Vater has a higher resectability rate and a much better survival rate than pancreatic cancer. Pancreaticoduodenectomy is the treatment of choice for this tumor. Long-term survival was independently influenced by the depth of tumor infiltration and lymph node metastasis.

Physical and chemical technologies have been continuously progressing advances in neuroscience research. The development of research tools for closed-loop control and monitoring neural activities in behaving animals is highly desirable. In this paper, we introduce a wirelessly operated, miniaturized microprobe system for optical interrogation and neurochemical sensing in the deep brain. Via epitaxial liftoff and transfer printing, microscale light-emitting diodes (micro-LEDs) as light sources and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-coated diamond films as electrochemical sensors are vertically assembled to form implantable optoelectrochemical probes for real-time optogenetic stimulation and dopamine detection capabilities. A customized, lightweight circuit module is employed for untethered, remote signal control, and data acquisition. After the probe is injected into the ventral tegmental area (VTA) of freely behaving mice, in vivo experiments clearly demonstrate the utilities of the multifunctional optoelectrochemical microprobe system for optogenetic interference of place preferences and detection of dopamine release. The presented options for material and device integrations provide a practical route to simultaneous optical control and electrochemical sensing of complex nervous systems.

LEDs that can be utilized as implantable light sources have been playing increasingly important roles in neuroscience research, along with the development of genetically encoded actuators and indicators. [3,4] In particular, gallium nitride (GaN)/indium gallium nitride (InGaN) based blue LEDs are utilized as implantable light sources for optogenetic stimulation and/or exciting fluorophores for neural signal sensing. [5,6] High performance GaN blue LEDs are typically grown on rigid, single crystalline substrates including sapphire, [7,8] silicon (Si) [1] and silicon carbide (SiC), [9] and novel strategies on growing and releasing GaN devices on unusual substrates like zinc dioxide coated graphene, [10] boron nitride (BN), [11] amorphous glasses, [12] nanovoid-mediated substrates, [13] etc. are also actively explored. [14] Although diced bare LED chips have found their uses in wearable and implantable systems by flip-chip bonding, [15,16] thinfilm LEDs (with thicknesses less than 10 µm) with various emission wavelengths that are released from original growth substrates and integrated onto flexible and stretchable substrates are more desirable for biomedical applications. [17] Recent results have successfully demonstrated that released, thinfilm LEDs are integrated with flexible, stretchable, and even biodegradable substrates with better biocompatibilities like improved skin conformance and reduced lesion during implantation. [5,18,19] Thin-film, freestanding red and infrared (IR) LEDs based on gallium arsenide can be easily formed by selective sacrificial etching; [20] however, conventional techniques for thinfilm GaN based purple/blue/green LED release and integration typically rely on sophisticated process steps including laser liftoff (LLO) (for GaN on sapphire), [21,22] chemical etching (for GaN on Si), [1,23,24] wafer bonding, [25][26][27] layer transfer, [11] device pick and place, [28,29] etc., [30,31] thus limiting their use. While GaN LED epitaxial liftoff and integration with flexible substrates have been extensively exploited for various planar device architectures like GaN LEDs on graphene, [7,10] BN, [11] glasses with nanovoids, [12,13] Si, [32] SiC-on-insulator, [9] the performance of these devices is still inferior to their counterparts on conventional sapphire substrates, in terms of their current-voltage characteristics, quantum efficiencies, etc. Therefore, it is highly desirable to develop simple and reliable technologies to implement the mainstream, state-of-the-art GaN LEDs (for example,