Human-machine interface (HMI) enabled by epidermal electronics system (EES)

1. Human-machine interface (HMI) enabled by epidermal electronics system (EES) ECE445 Senior Project Team #37: Woosik Lee, Ohjin Kwon, Nithin Reddy

2. Introduction • The micro/nanotechnology development has access to many types of motion sensors • Human motions can be directly translated into the controlling system by directly mounting the electronic system onto skin epidermis

3. Features • EES that has the matching mechanics to the skin epidermis • Portable Signal Conditioning Unit • Easy programmable microcontroller

4. System Overview

5. EES Electrodes Integrating Conventional to EES electrodes

6. Fractal Design • Def.: self-similar and recursive structure in naturethat can fill space with increasing iteration • To provide design criteria for stretchable, biomedical devices

7. Micro Fabrication Spincoated PR ③ ① ② Evaporated Au Spincoated PI PI PI PI PI PI PI PI Au PDMS PDMS PDMS PDMS PDMS PDMS PDMS PDMS PDMS Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Si Wafer Encapsulated PI Developed PR ④ Etched Au ⑤ ⑥ Au Spincoated PR Developed PR ⑦ ⑨ ⑧ Etched PI

8. Transferring • Pick up EES electrodes by water soluble tape • Laminate on thin ecoflex (silicon) as a substrate • ACF cable connection • Solder wires on PCB board that connects EES electrodes with amplifier REC GND REF

9. Verification • Measurement result 1 : Thickness less than 2µm • Thickness dependency of conformal contact on skin • Use electron beam (e-beam) evaporator and choose the right rpm & time of spinner.

10. Verification • Measurement result 2 : Noise to ratio • Range within -1mV to +1mV

11. Verification • Measurement result 3 : Detecting EMG • Bending fist makes enough EMG signal Stable Bending

12. Verification • Measurement result 4 : Spatial Actions • Four spatial actions can be classified as distinct motions using two EES electrodes on each forearm.

13. Verification • Measurement result 5 : Stretchability • Observe plasticity point about 20% of stretching by using stretcher and lock-in amplifier.

14. Signal Conditioning Unit • Receive the signal from E.E.S. • Detect signal & Amplify gain 10000. • Filter 10Hz ~ 500Hz (E.M.G. cut off frequency) • Filter noises

15. Overall Schematic, Eagle

16. Instrumentation Amplifier • Type of amplifier that eliminates the need for input impedance matching • Increase the gain, 10000.

17. 620 Instrumentation Amplifier • Instrumentation amplifier • Outfitted with input buffer • Main amplifier • Low power, Suitable, High open-loop gain • REF - Virtual short voltage - From 741 op amp - G = V0/(Vpin1-Vpin8)

18. 741 Operational Amplifier • Consists of differential input, single-ended high gain stage, output buffer, one capacitor. • 741 op amp + Capacitor + Register → Low Pass Filter 1. Filtering signal from 620 amp 2. Voltage cancel (signal go into REF of 620 amp)

19. (Negative) Feedback • Reduce the effect of noise • Desensitize the gain • Increase filtering coefficient with extra poles • Control terminal impedances • Reduce non-linear distortion • Bandwidth extension

20. Band-pass Filter • Filtering ↓10 Hz & ↑500 Hz • 4th order LPF & 1st order HPF

21. Low-pass Filter • Attenuating above 500 Hz signal • 4th order low-pass filter

22. More steeply, more filtering

23. High-pass Filter • Attenuating below 10 Hz signal

24. Verification • PSPICE program • Low-pass filter, cut off frequency = 500Hz

25. Verification • PSPICE program • High-pass filter, cut off frequency = 10Hz

26. Overall Schematic, PCB board

27. Portable PCB board

28. Power Supply • Signal Conditioning Unit • Each chip ≥4.8v • Two 5 volt batteries • Supplies to +Vs and –Vs • Microcontroller • 5v

29. Microcontroller • Arduino Uno was used. • Consists of a 10 bit Analog to Digital Convertor. • Analyze & Convert the signal from S.C.U. • Atmega16U2programmed as a USB-to-serial converter. • Derives power from USB. • Easily Programmable.

30. Microcontroller Implementation • Input is received from the S.C.U. • Reads the input signal and determines the amount of voltage generated by muscle of the user. • Transfers data to computer through USB . • Displays direction that user intends to move robot using visualization software.

31. Microcontroller commands

32. Software • Arduino Software Input from the S.C.U is received on the input pin A0 and sends out voltage through COM port(USB) to computer • Processing Software The computer receives the signal from the Arduino through the USB and displays the signal on a threshold graph and prints out direction that user moves muscle.

33. Arduino Software • Takes in Input from the S.C.U from pin A0. • Reads the analog input . • Displays the signal on the serial monitor . • Transfers the data through COM 5 to the computer.

34. Arduino Program

35. Processing Software • Displays received input signal on a threshold graph. • Bar on graph shifts as muscle is flexed by the user. • Program displays the action of the user based on the how far the bar moves on the graph.

36. Processing Program

37. Microcontroller Testing • Tested using a conventional potentiometer. • Potentiometer connected to the input pin A0. • Ran the Processing and Arduino software with this input. • Observed the graph and checked if the bar moves as we turn the knob of the potentiometer. • Observe if the program prints out a direction if the bar is within the respective ranges.

38. Verification

39. Demonstration • PCB board was burned • Reason • Was not connected with GROUND • Solution • Used conventional amplifier instead • Disadvantage • Already set up for PCB board

40. Conventional Amplifier

41. Challenges • Delay on manufacturing PCB board • A low yield producing EES electrodes • High noise level of EES electrodes depending on device quality

42. Future Work • Prepare two sets of SCU component for each arm • Develop EES RF antenna that sends EMG signal wirelessly to SCU • Small size packaging of SCU and microcontroller • Develop program that connects microcontroller and controllable machine on computer

43. Credits Thanks to • Professor Scott Carney • Mrs. Lydia Majure • Mr. Jamie Norton • Dr. Hong and Dr. Jeong from Rogers Research Group • Laboratory for Optical Physic and Engineering (LOPE)