Wireless, skin-interfaced sensors for compression therapy

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Science Advances  04 Dec 2020:
Vol. 6, no. 49, eabe1655
DOI: 10.1126/sciadv.abe1655
  • Fig. 1 Design and characterization of a wireless device for monitoring the treatment of VLUs with compression stockings.

    (A) Schematic, exploded-view illustration of an SCV with constituent layers and components: silicone elastomer, battery, BLE SoC, Wheatstone bridge circuits configured with a 3D pressure sensor (Rp) and a temperature sensor (RT), and circuit traces (copper/PI). (B) Circuit and block diagrams of the system and its wireless interface to smartphones. Analog front-end circuits consist of two differential AMPs and Wheatstone bridge circuits including resistive sensors (RP and RT) and reference resistors (R, RP0, and RT0). A central processing unit (CPU) transmits the ADC-sampled data (pressure/temperature measurements; VP and VT) via BLE radio to user interfaces (smartphones). (C) Photographs of SCV on the leg of a healthy patient (left) and with compression stocking (right). (D) Photograph of SCV during bending and twisting. (E) Computed strains along the copper traces and the components on the flexible printed circuit board (FPCB) in twisted (left) and bent (right) configurations. Photo credit: Yoonseok Park, Northwestern University.

  • Fig. 2 Design and characterization of a 3D pressure sensor.

    (A) A tilted exploded view layout of the constituent layers of the 2D precursor consists of a top and bottom PI layer and gold layer (trace in a serpentine geometry; width, 3 μm; thickness, 50 nm; resistance, 2.1 kilohms). (B) Photographs and FEA-predicted results of a 2D precursor (left) and corresponding 3D structure (right) after a compressive buckling process. (C) Schematic exploded view illustration of a pressure sensor that consists of PI layers, acrylic ring, FPCB, and a 3D structure encapsulated in a transparent elastomer. FEA-predicted results and (inset) magnified view of changes in strain distributions across a metal strain gauge (D) and a photograph (E) of a 3D structure under compressive strain. (F) Change in resistance of a 3D structure under compressive strain (0, 12, and 24%), with insets that show FEA results. Photo credit: Yoonseok Park, Northwestern University.

  • Fig. 3 Performance characteristics of a 3D pressure and temperature sensor.

    (A) Fractional change in resistance of a 3D pressure sensor as a function of normal pressure loading. RT, room temperature. (B) Measurement of the temporal response of a sensor and overlaid responses during applying and removing pressure (inset). (C) Fractional change of resistance at different stages of fatigue testing with a speed of 50 and 200 μm/s (loading and unloading) over 1000 cycles. (D) Response of an NTC temperature sensor as a function of temperature of a supporting substrate measured using an IR camera. (E) IR photograph of an SCV on the leg at two time points after mounting. (F) Temperature of the SCV before and after mounting on the skin and after removal.

  • Fig. 4 Evaluations of a wireless 3D pressure sensor and a reference device performed with a DMA and with a compression stocking mounted on the legs of healthy volunteers.

    (A) Photograph of a wireless sensor and a reference sensor (PicoPress, Microlab) of pressure. Changes in the resistance of the 3D sensor and response of the reference equipment as a function of pressure on a (B) flat rigid surface, (C) flat elastic surface, and (D) curved elastic surface with different materials [elastomers with different elastic modulus; Dragon Skin 10 (E = 137 kPa), Ecoflex 00-50 (E = 83 kPa), and Ecoflex 00-30 (E = 69 kPa)]. (E) Schematic illustration of eight measurement points across the leg. Measured changes in pressure and resistance on the leg of a healthy volunteer using a compression stocking at pressures of (F) 15 to 20 mmHg and (G) 20 to 30 mmHg. Pressure measurement using the SCV and the reference equipment during (H) resting, (I) walking and running, and (J) cycling with speeds of 60 and 120 rpm. Photo credit: Yoonseok Park, Northwestern University.

  • Fig. 5 Pressure and temperature measurements obtained using a wireless 3D pressure/temperature sensor during daily activities with a compression stocking.

    Pressure and temperature measurements while (A) in a sitting position, (B) walking indoors and outdoors, (C) cycling at a self-selected low (16 km/hour) and high (25 km/hour) speed, and (D) sleeping for 6 hours.

  • Fig. 6 Clinical studies of interface pressure measured by SCV and reference devices from eight patients with different pathologies.

    Photographs of measurement locations on the leg of a patient and pressures measured by SCV and reference devices at locations C2 and C4 (A and B) and C1 and C3 (C and D) on the left (L) and right (R) legs of patients using compression stockings. Photographs of the right leg and changes in pressure of a patient with varicose veins (E and F). (G) Photographs of the left leg and the VLU of a patient and measured pressures for 2 weeks (H). (I) Bland-Altman plot comparing results from the SCV and reference devices. Photo credit: Brianna R. Kampmeier, Northwestern University.

Supplementary Materials

  • Supplementary Materials

    Wireless, skin-interfaced sensors for compression therapy

    Yoonseok Park, Kyeongha Kwon, Sung Soo Kwak, Da Som Yang, Jean Won Kwak, Haiwen Luan, Ted S. Chung, Keum San Chun, Jong Uk Kim, Hokyung Jang, Hanjun Ryu, Hyoyong Jeong, Sang Min Won, Youn J. Kang, Michael Zhang, David Pontes, Brianna R. Kampmeier, Seon Hee Seo, Jeffrey Zhao, Inhwa Jung, Yonggang Huang, Shuai Xu, John A. Rogers

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