E-textile based modular sEMG suit for large area level of effort analysis

Abstract

We present a novel design for an e-textile based surface electromyography (sEMG) suit that incorporates stretchable conductive textiles as electrodes and interconnects within an athletic compression garment. The fabrication and assembly approach is a facile combination of laser cutting and heat-press lamination that provides for rapid prototyping of designs in a typical research environment without need for any specialized textile or garment manufacturing equipment. The materials used are robust to wear, resilient to the high strains encountered in clothing, and can be machine laundered. The suit produces sEMG signal quality comparable to conventional adhesive electrodes, but with improved comfort, longevity, and reusability. The embedded electronics provide signal conditioning, amplification, digitization, and processing power to convert the raw EMG signals to a level-of-effort estimation for flexion and extension of the elbow and knee joints. The approach we detail herein is also expected to be extensible to a variety of other electrophysiological sensors.

Figure 1

(a) Subject wearing the final sEMG suit showing arm sleeves, shorts, and calf sleeves. Fabrication of top side of the sEMG sleeves showing an (b) exploded view of sleeve stack up and (c) image of the assembled sleeve.

Figure 2

Preliminary don-doff strain testing of completed sleeves showing. (a) Image of sleeves showing the printed silver, thick, pre-strained, wide, and CCSM configurations (from left to right). (b) Ground resistance below 600 Ω versus don cycle. Bright field optical microscope images of (c) printed silver after strain and (d) CCSM under strain. Scale bar represents 100 µm.

Figure 3

Strain cycling results showing the (a) short sine interconnect design, (b) tall sine interconnect design, (c) short nested interconnect design, and (d) tall nested interconnect design. Scale bar represents 2 cm. (e) Resistance versus cycle number at 25% strain over 1000 cycles (n = 3 coupons).

Figure 4

Robustness testing of finalized interconnect geometry showing (a) end to end resistance of CCSM leads for each muscle group versus don-doff cycle, (b) end to end resistance of CCSM leads versus machine laundering cycles (n = 4 electrode interconnects), and (c) sheet resistance of CCSM versus simulated hours of exposure to UV (n = 3 coupons, inset image of sample test coupon with exposed region enclosed).

Figure 5

Characterization of PEDOT:PSS and CCSM electrodes. SEM image of (a) polyester impregnated with PEDOT:PSS and (b) CCSM. (c) Schematic of electrode stack up. (d) Impedance measurements of PEDOT:PSS and CCSM when dry and wet at 1 kHz (n = 2 coupons). Sheet resistance of PEDOT:PSS and CCSM versus (e) cumulative abrasion time (n = 3 coupons) and (f) laundering cycles (n = 5 coupons).

Figure 6

Finalized arm sleeve design showing the (a) labeled image of the interior and exterior of the sleeve, (b) schematic of tall nested interconnect design showing e-textile (gray/dark) and protective TPU (blue/light, dimensions in mm), and (c) image of the flex tab in the optional custom built glass filled nylon enclosure. Exemplar elbow flexion EMG plot from the arm sleeve showing (d) raw data and (e) filtered data.

Figure 7

Human subject research testing of sEMG suit with 1 degree of freedom system. Images of experimental set-up for (a) the bicep/tricep (elbow), (b) quadriceps/hamstring (knee), and (c) tibialis anterior/gastrocnemius (ankle) muscle groups (joints). (d,e) Human subject research data showing 1-way ANOVA results for binned level of effort verification for elbow, knee, and ankle extension exercises, respectively (n = 10 trials). Red crosses indicate outliers.

Figure 8

Multi-day comparison of muscle activation during isolated elbow exercises. Red crosses indicate outliers.