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Abstract Cisplatin, the first platinum chemotherapy agent to obtain Food and Drug Administration (FDA) approval in 1978, is widely used for a number of cancers. However, the painful side effects stemming from systemic delivery are the inevitable limitation of cisplatin. A possible solution is regional chemotherapy using various drug delivery systems, which reduces the systemic toxicity and increases drug accumulation in the tumor. In this paper, a rice‐grain sized, ultrasonically powered, and implantable microdevice that can synthesize cisplatin in situ is presented. The microdevice produces 0.7 mg of cisplatin within 1 h under ultrasonic irradiation (400 mW cm⁻²). The effect of the microdevice‐synthesized cisplatin is evaluated using in vitro murine breast cancer cells and ex vivo liver tissue. The results suggest that cytotoxic activities of the microdevice‐mediated cisplatin delivery are significantly higher in both in vitro and ex vivo experiments. Overall, the proposed cisplatin synthesis microdevice represents a strong alternative treatment option for regional chemotherapy 

Ultrasonic powering is an emerging power source for implantable microdevices due to its superior efficiency in energy transfer at millimeter-scale, long operation distance, and near omnidirectionality. In this paper, we investigate a novel polyhedral ultrasound transducer with emphasis on angular alignment between piezoelectric poling vector and incident waves. Three different polyhedrons (i.e., sphere, octahedron, and dodecahedron) are fabricated via 3D printing lead-free barium titanate ceramic. The maximum output voltage for a unit area occurred at 0° when the poling and waves direction aligned, which were measured to be 0.677±0.071,1.058±0.049 , and 0.709±0.092 V , respectively. At the extreme angular misalignment at 90° (poling and waves perpendicular to each other), only the dodecahedron could sustain the voltage output with 21% reduction, whereas sphere and octahedron dropped by 46%. The results imply that the geometry factor may overcome the poling vector, enabling omnidirectional ultrasonic powering for implantable microdevices. 

Continuous monitoring of biochemical information is critical for health management. Hydrogel, a synthetic material that exhibits volumetric response to target stimuli, is an attractive material for such applications. However, wireless readout of the hydrogel's response over a longer distance, while maintaining the small sensor dimension has been challenging. In this work we present ferrogel-based wireless acousto-biochemical sensing system with small dimension (length: 7.5 mm, diameter: 2 mm) and long sensing distance (>10 cm). The sensor utilizes ferromagnetic hydrogel to convert pH to the change in resonance frequency; the wireless measurement is made through the RF signal emission under ultrasonic excitation. 

In this paper, we introduce an oral motion-powered Smart Tooth system that can monitor oral health. Lower pH is an indicator of bacterial accumulation in the oral cavity, which can cause tooth decay, periodontal or peri-implant diseases. Thus, in situ monitoring pH inside of the mouth is critical to prevent oral diseases. Using a piezoelectric dental crown, Smart Tooth system converts oral motions, such as chewing, to electrical power which can impinge a surface integrated LC transponder. The LC transponder also incorporates iron oxide nanoparticles-embedded pH-sensitive hydrogel that modulates the resonant frequency via shrinking or swelling. As a proof of concept, the fabricated prototype measures pH levels ranging from pH 4 to 12 and sends data wirelessly to the receiver placed up to 5 cm away (wireless transmission path loss at 3 cm was 50.79 dB). The results indicate that the Smart Tooth system can monitor oral health while replacing missing teeth. 

In this work, we present a proof-of-concept hydrogel-based sensor system capable of wireless biochemical sensing through measuring backscattered ultrasound. The system consists of silica-nanoparticle embedded hydrogel deposited on a thin glass substrate, presenting two interfaces for backscattering (tissue/hydrogel and hydrogel/glass), which allows for system output to be invariant under the change in acoustic properties (e.g. attenuation, reflection) of the intervening biological tissue. We characterize the effect of silica nanoparticles (acoustic contrast agents) loading on the hydrogel's swelling ratio and its ultrasonic backscattering properties. We demonstrate a wireless pH measurement using dual modes of interrogations, reflection ratio and time delay. The ultrasonic hydrogel pH sensor is demonstrated with a sensing resolution of 0.2 pH level change with a wireless sensing distance around 10 cm.