The main results are divided in 3 different blocks which correspond to the 3 work packages (WP) of the proposal:
1) WP1. Design and fabrication of microfluidic platforms
We published the fabrication of the second-generation devices using glass as an alternative material to polydimethylsiloxane (PDMS), Nature Communications, 2019, 10, Article number: 1439. This achievement was crucial for the µ-CrysFact project because as proposed in the Description of the action (Task 1.2.ii) even though the materials considered in µ-CrysFact are PDMS-compatible, we could also implement a contingency plan that included the fabrication of microfluidic devices made of glass. Note that this accomplishment will now allow to meet the chemical/solvent resistant requirements to study other molecular-based systems that are not PDMS-compatible in our group. Additionally to these microfluidic devices, we have recently patented a nanoreactor approach that enables the preparation of unique porous crystalline nanoparticles. The patent is entitled “‘Nanoreactors for the synthesis of porous crystalline materials”, also see J. Am. Chem. Soc., 2020, 142, 3540-3547.
On the other hand, we have also prepared a microfluidic device that allows a high-throughput combinatorial sample preparation to optimize the performance of organic solar cells (Adv. Energy Mater. 2020, 2001308). The results obtained indicate that a single sample prepared with our method can rapidly denote which conditions are necessary to yield the optimum device performance. These results are in line with one of the outcomes of the project (see section below), i.e. the localization of multiple functional materials in a single surface. In this latter outcome of the project, we have also used the third-generation platforms to control the growth and localization of functional matter as indicated in the project, see e.g. Advanced Science, 2020, 1903172.
2) WP2. Self-assembly studies under controlled dynamic conditions
We have reported that these devices allow diffusion-limited and kinetically controlled environments which could be crucial to unveil the pathway followed by a molecular-based system during its formation (Crystals, 2019, 9, 12; doi:10.3390/cryst9010012) or additionally could be key to achieve out-of-equilibrium assemblies which may display different functions than their thermodynamic counterparts (Chem. Soc. Rev., 2018, 47, 3788-3803).
In WP2, we have already studied different metal-organic based compounds. Initially, demonstrated that the devices produced in WP1 uncover different crystallization pathways undertaken by the same MOF system towards its thermodynamic product. Specifically, microfluidic mixing (providing kinetic control) enables two peculiar nucleation-growth pathways characterized by well-defined metastable intermediates, which have never been observed in bulk environments (under thermodynamic control). These results are unprecedented and provide a sound basis for understanding coordination polymer growth and open new avenues for the engineering of advanced functional materials (Angew. 2021, 60, 15920). Indeed, we have demonstrated that controlling and generating kinetically controlled environments can be key to master chiral symmetry breaking processes, see e.g. Nat. Commun., 2022, 13, 1766.
Moreover, we show that while the bulk synthesis of complex [Fe(Htrz)2(trz)]n(BF4)n uniformly yields a crystalline thermodynamic product, exhibiting a single abrupt spin transition, its synthesis with first generation devices leads to an amorphous non-equilibrium state that displays a radically different transition from a low spin (LS) to a high spin (HS) state. This manuscript has been submitted.
Additionally to these works, we have also studied how derivatization of crystals can be performed by using a laser-induced doping (Carbon, 2018, 130, 48-58), and we have investigated the biocompatibility characteristics of a metal-organic material for applications as a drug delivery agent (Applied Materials Today, 2018, 11, 13-21, Adv. Mater. 2019, 1901592, Angew. Chem. Inter. Ed. 2019, 58,13550-13555, J. Am. Chem. Soc., 2020, 142, 20, 9372-9381, Adv. Healthcare Mater. 2020, 2001031, Adv. Mater. 2021, 33, 2101777, Adv. Funct. Mater., 2021, 2107421). These two last investigations have been important to achieve Task 3.2 ‘On-crystal engineering’ and Task 3.3. Multifunctionality.
3) WP3. Mastering self-assembly on surfaces and ‘on-crystal engineering’ by microfluidic means
We wrote two papers based on these devices. In one, we showed that this third generation of microfluidic devices are very efficient to achieve a spatial localization of surface-enhanced Raman scattering (SERS) substrates as well as Raman probe molecules to specific detection points along a single microfluidic channel, preventing cross-contamination and endowing multiple detection capabilities (Advanced Science, 2020, 1903172).Recently, we have also shown that the first generation of devices can be used to control the growth, positioning and integration of metal-organic crystals on surfaces where an advance mass transport of reagents is ensured. This method has been termed “In-flow MOF lithography” (Adv. Mater. Technol. 2019, 1800666).
