Electrical stimulation towards melanoma therapy via liquid metal printed electronics on skin.

BACKGROUND: We proposed a method of using electrical stimulation for treatment of malignant melanoma through directly spray-printing liquid metal on skin as soft electrodes to deliver low intensity, intermediate frequency electric fields. METHODS: With patterned conductive liquid metal components on mice skin and under assistance of a signal generator, a sine wave electrical power with voltage of 5 V and 300 kHz could be administrated on treating malignant melanoma tumor. FINDINGS: The experiments demonstrated that tumor volume was significantly reduced compared with that of the control group. Under the designed parameters (signal: sine wave, signal amplitude Vpp: 5 V and Vpp: 4 V, frequency: 300 kHz) of Tumor treating fields (TTFields) with the sprayed liquid metal electrode, four mice tumor groups became diminishing after 1 week of treatment. The only device-related side effect as seen was a mild to moderate contact dermatitis underneath the field delivering electrodes. The SEM images and pathological analysis demonstrated the targeted treating behavior of the malignant melanoma tumor. Further, thermal infrared imaging experiments indicated that there occur no evident heating effects in the course of treatment. Besides, the liquid metal is easy to remove through medical alcohol. CONCLUSIONS: Tumor treating fields through liquid metal electrode could offer a safe, straightforward and effective treatment modality which evidently slows down tumor growth in vivo. These promising results also raised the possibility of applying spray-printing TTFields as an easy going physical way for future cancer therapy.

A third-order mode high frequency biosensor with atomic resolution.

An atomic resolution ultra-high sensitivity surface acoustic wave (SAW) biosensor for DNA sequences and cells detection is proposed. Interdigitated transducers (IDTs) fabricated on LiNbO3 substrate achieve a high quality factor (Q) of over 4000 at a frequency of 6.4 GHz (third-order harmonic mode) using an optimized design and process. The biosensor shows excellent linear responses to target DNA in the range from 1 µg/ml to 1 ng/ml with a high sensitivity of 6.7 × 10(-16)g/cm(2)/Hz, hence the difference of a single hybridized DNA base can also be distinguished. With such a high mass resolution, the biosensor is capable of quantitative detection of living cancer cells. The frequency responses of single mouse mammary adenocarcinoma (EMT6) cell and mouse fibroblast (3T3) cell are studied. The interferences in the experiments show insignificant influence on the frequency shift, which verifies the high selectivity of the biosensor. The biosensor is also able to repeat the sensing ability after rough cleaning, therefore cost reduction is achieved from the recycling process in practical applications. The detection limit is defined from the noise analysis of the device, atomic resolution is realized according to the calculation, thereby initiating a potential tool for high-precision medical diagnoses and phenomena observation at the atomic-level.

Rapidly patterning conductive components on skin substrates as physiological testing devices via liquid metal spraying and pre-designed mask.

The newly emerging skin-electronic devices with flexible features are usually fabricated on a very thin substrate, which do not directly contact the skin. This may generate large coupling impedance with the skin and a high signal noise for a sensitive detection of weak physiological signals. Here, in an alternative manner, we propose a method to directly pattern liquid metal conductive components as sensors on skin through a spray-printing strategy. This quick way of making flexible electronics on skin is enabled via a stainless mask that is pre-designed by chemical etching with line width resolution of 100 µm and can be used to deposit desired electrical components. Several typical geometric metal graphics, spanning from simple to complex structures, which serve to compose complex electrical circuits or devices, are fabricated in a moment. Particularly, GaIn24.5-based liquid metal wires deposited on pig skin under different conditions were quantified, and the mechanisms for the spray-printing of bioelectronics were interpreted. Further, stretching experiments were performed, which show that the resistance of the printed film would take a square growth with the tensile length of the pig skin in a specific range. Finally, an inter-digital array (IDA) electrode sensor with the distance between two inter-digital fingers of 0.5 mm and the length of the finger of 11 mm was fabricated and applied to measure impedance spectroscopy of pig skin. This study demonstrates the unique value of the present Lab on Skin for physiological measurement. It illustrates a promising route for directly printing electronics pattern on skin that will be very useful for a wide variety of practical situations such as skin sensors, actuators, skin electrical circuits, etc.