title: Electrical stimulation towards melanoma therapy via liquid metal printed electronics on skin.
abstract: 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.
  
  
  RESULTS
  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.
authors.affiliation: Department of Dermatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100730, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, 100084, People's Republic of China.
authors.forename: Cangran
authors.initials: C
authors.lastname: Guo
authors.affiliation: Department of Dermatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100730, People's Republic of China.
authors.forename: Zhongshuai
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, People's Republic of China.
authors.forename: Kai
authors.initials: K
authors.lastname: Gao
authors.affiliation: Institute of Laboratory Animal Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100021, People's Republic of China.
authors.forename: Xudong
authors.initials: X
authors.lastname: Shi
authors.affiliation: Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, 100084, People's Republic of China. jliubme@tsinghua.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
keywords: Electrical therapy; Liquid metal electrode; Melanoma therapy; Skin soft electronics; Tumor treating fields