Section 1: Morphologies of materials

Figure S1 shows the morphologies of MWCNTs, PDMS and MPC. As shown in Fig. S1(a), MWCNTs show a high length-diameter ratio and get tangled up with each other. It is attributed to the Van der Waals force between MWCNTs. Consequently, MPC show much rougher surface than pure PDMS due to the internal agglomeration of MWCNTs, as shown in Fig. S1(b) and Fig. S1(c).

Section 2: Evaluation of mechanical properties

The mechanical evaluation system is shown in Fig. S2.

The strain along stretching direction (ε_z) is calculated as Eq. S1:

$ \tag{S1} {\varepsilon _z} =\frac{{ {\rm{\Delta}} L }}{{{L_0}}} \times 100\%, $ (S1)

where ${\rm{\Delta}} L$ and ${L_0}$ refer to the length variation and original length of the testing sample, respectively.

On the cross section of the testing sample, the width w and thickness t direction (ε_x) are calculated as Eq. S2:

$ \tag{S2} \frac{{w }}{{{w_0}}} = \frac{{t }}{{{t_0}}} , $ (S2)

where w₀ and ${t_0}$ refer to the original width and original thickness of the testing sample, respectively.

The tensile stress (σ_z) is calculated as Eq. S3:

$ \tag{S3} {\sigma _z} = \frac{{{F_z}}}{{{w}{t}}}\;, $ (S3)

where ${F_z}$ refers to tensile force.

The relationships of ε_z and σ_z can be described by Young's modulus (E), as shown in Eq. S4:

$\tag{S4} {\sigma _z} = E{\varepsilon _z}\;,$ (S4)

Consequently, E of testing samples can be evaluated by slopes of σ_z-ε_z curves.

Section 3: Variation of laser power and pulse with frequency

Figure S3 shows the variation of laser power and pulse with repetition frequency at Q = 1. Laser pulse is increased with the increase of repetition frequency. When repetition frequency is below 80 kHz, laser power increases with the increasing repetition frequency. When repetition frequency exceeds 90 kHz, laser power decreases with the increasing repetition frequency.

Section 4: SEM images of microstructures fabricated with different laser parameters

Figure S4 shows surface morphologies of the microstructures fabricated with different laser parameters. When laser repetition frequency varied from 35 kHz to 45 kHz, laser power varied in an approximate range of 2~5 W, which brought about significant impacts in morphology of microstructures. When laser scanning speed varied from 100 mm·s^-1 to 200 mm·s^-1, obvious difference in morphology of the microstructures could be found, which can be attributed to the significant variation in the laser energy density. When laser repetition frequency was below 40 kHz, laser path can be found on the substrates and the microstructures had relative small size. When laser repetition frequency was set to 45 kHz, the laser path disappeared from substrates because a higher energy density induced significant ablation and quantities of particles can be found around the microstructures, which indicated destruction to the microstructures.

Section 5: Sensitivities of flexible piezoresistive sensors fabricated by different laser parameters

Figure S5 shows sensitivity of flexible piezoresistive sensors fabricated by different laser parameters. Laser parameters significantly affected the sensitivity and the performance of flexible piezoresistive sensors through modulating the surface morphologies of microstructures.

Section 6: Supplementary videos

Video S1. Resistance variation of the flexible piezoresistive sensor for dynamic pressure about 2 kPa.

Video S2. Application of the piezoresistive sensor in LED brightness controlling by finger pressing.

Video S3. Resistance variation of the flexible piezoresistive sensor in wrist pulse detection.

Video S4. Resistance variation of the flexible piezoresistive sensor in voice recognition.

Section 7: Supplementary tables