Sylgard 184

The preparation of the striated substrate is based on the soft lithography and micromoulding techniques as generally described in [35 (link)], and specifically applied to electrospun nanofiber mechanical measurements in [31 (link),32 (link),33 (link),34 (link)]. First, a PDMS (polydimethylsiloxane) stamp (negative (inverted) relief structure of the striated substrate) was created by pouring dimethyl siloxane mixed with a catalyst (Sylgard^® 184, Sigma-Aldrich, St. Louis, MO, USA) onto an SU-8-silicon master grid in a large plastic Petri dish. A 1 cm × 1 cm stamp can then be excised with a scalpel. Excised stamps were stored in a 2% sodium dodecyl sulfate (SDS) solution to keep them clean; the stamps can be stored for at least several months and used repeatedly. To create the striated substrate, a drop of Norland Optical Adhesive-81 (NOA-81, Norland Products, Cranbury, NJ, USA) was placed on a 60 mm × 24 mm, #1.5 microscope cover slide (Thermo Fisher Scientific, Waltham, MA, USA). The PDMS stamp was pressed into the NOA-81 drop on the slide and cured with 365 nm UV light (Benchtop 3UV transilluminator, UVP, Upland, CA, USA) for several minutes. The substrate had ridges of width 7.3 μm and height 6 μm. The gaps between the ridges were 6 μm across.

All prepolymers were prepared in liquid state for uniform dispersion. PSPI (PIP 100, PNS technology, Anyang, Korea) was added to PDMS base and its cross-linking agent (Sylgard 184, Sigma-Aldrich, St. Louis, MO, USA) and then magnetically stirred for about 5 min. The mixtures were prepared by adjusting the weight ratio (PDMS:PSPI = 20:1, 10:1, 5:1, and 5:2). As-prepared mixtures was transferred onto silicon wafer (4SWP06, Prime grade, Silicon Technology Corp, Tokyo, Japan) and then spin-coated at 500 rpm for 1 min. Subsequently, the sample was cured for 1 h at 200 °C on a hot plate and then cooled to room temperature.

The paracetamol/HCl sensing
and cleaning experiments are carried out on a MLagg film deposited
on a coverslip (Menzel #1.5). The MLagg films are prepared according
to the standard protocol but re-scaffolded with CB[7] molecules instead
of CB[5]. The films on the coverslip are then plasma bonded to a PDMS
chip (AuNP films face inside the channels of the chip) by a short
exposure (a few seconds) to oxygen plasma. Briefly, the PDMS chip
is manufactured by standard soft lithography from a template master
mold. For the process, the SU-8 2100 negative photoresist is spin-coated
evenly onto a silicon wafer to yield a layer height of ∼150
μm. After additional baking and exposure to UV light (through
photomask), the photoresist is developed by immersing the wafer into
PGMEA (1-methoxy-2propanol acetate) and then hard baked. A PDMS kit
(SYLGARD 184, Sigma-Aldrich) with a mixing ratio of 1:10 (curing agent
to PDMS monomer base) is used to manufacture the chips (baking for
30 min at 120 °C after degassing). For flow experiments, two
inlets and one outlet are punched (1 mm diameter) into the PDMS chip.
The inlets are connected to custom-made syringe pumps containing HCl
(1 M) and paracetamol (1.5 mM) solutions. Kinetic SERS measurements
are taken through a 63× (NA = 1.2) water-immersion objective
with 0.5 s integration time. The liquid flow is cycled between paracetamol
and HCl for 20 s each.^{48 (link)}

After fine dissection, pancreases were fixed in 4% paraformaldehyde for 3 hours either directly (endocrine pancreas anatomy and semi‐quantitative pancreas neurofilament density) or after stretching (PINS ganglia phenotype). Stretching consisted in pinning the pancreas flat in a dish lined with silicone (Sylgard^®184; Sigma‐Aldrich, St Quentin Fallavier, France).7

To eliminate the experimental error of mixing the base and curing agent, PDMS (SYLGARD® 184) with a fixed base and curing agent ratio of 10:1 is purchased from Sigma-Aldrich. For experiments to investigate the ratio influence and the pattern copy, PDMS (SYLGARD® 184) is purchased from Dow Corning, where the weight ratio of the base to curing agent can be varied. NOA 63 resist is purchased from Norland Products Inc. Perfluorodecyltrichlorosilane (FDTS) is bought from Alfa Aesar. Materials for OLED devices are purchased from Luminescence Technology Corp. and used after sublimation.