Microneedles (MNs) are an emerging technology in pharmaceutics and biomedicine, and are ready to be commercialized in the world market. However, solid microneedles only allow small doses and time-limited administration rates. Moreover, some well-known and already approved drugs need to be re-formulated when supplied by MNs. Instead, hollow microneedles (HMNs) allow for rapid, painless self-administrable microinjection of drugs in their standard formulation. Furthermore, body fluids can be easily extracted for analysis by a reverse use of HMNs, thus making them perfect for sensing issues and theranostics applications. The fabrication of HMNs usually requires several many-step processes, increasing the costs and consequently decreasing the commercial interest. Photolithography is a well-known fabrication technique in microelectronics and microfluidics that fabricates MNs. In this paper, authors show a proof of concept of a patented, easy and one-shot fabrication of two kinds of HMNs: (1) Symmetric HMNs with a “volcano” shape, made by using a photolithographic mask with an array of transparent symmetric rings; and (2) asymmetric HMNs with an oblique aperture, like standard hypodermic steel needles, made by using an array of transparent asymmetric rings, defined by two circles, which centers are slightly mismatched. Simulation of light propagation, fabrication process, and preliminary results on ink microinjection are presented.

The incorporation of azobenzene chromophores into polymer systems gives rise to a number of unique effects under UV and visible light irradiation. The light-driven isomerization of the azobenzene element acts as a light-to-mechanical energy converter, translating the nanoscopic structural movement of the isomerization azobenzene into macroscopic topographic film modulation in the form of surface relief. This review focuses on the study of reversible changes in shape in various systems incorporating azobenzene, including large-scale superficial photo-patterned glassy materials, light-driven reshaping of tridimensional superficial azo-textures and contractions of stimuli-responsive liquid crystalline networks (LCNs). Further, promising applications of azo systems are investigated as smart biointerfaces able to mimic time-varying biological systems.

Interstitial fluid (ISF) extraction and analysis are challenges that can be tackled by Hollow MicroNeedles (HMNs) technology, overcoming most of the difficulties associated with in situ detection. Herein, a plasmonic transducer, composed of gold nanoparticles embedded in poly(ethylene glycol) diacrylate (PEGDA) hydrogels, is integrated in the inner cavity of HMNs to detect biomarkers from the ISF‐based point‐of‐care. The wearable HMN‐based patch is used for minimally invasive pierce of the skin. The large swelling capability of the plasmonic transducer allows the uptake of ISF by capillarity. Biotin, as a small model molecule, is efficiently collected in the inner cavity of HMN and its high specificity with the streptavidin is exploited as a validation of the plasmonic nanocomposite functionality embedded within. The recognition of biotin is achieved in dual‐optical mode: the localized surface plasmon resonance (label‐free) and the metal‐enhanced fluorescence (label‐based). Overall, the proposed HMN‐based patch for target sensing in ISF can represent a novel point‐of‐use device for the detection of biomarkers as an alternative to conventional hospital or lab settings to help faster medical decision‐making.

The ability to affect a wide range of biophysical properties through the use of light has led to the development of dynamic cell instructive materials. Using photoresponsive materials such as azopolymers, smart systems that use external, minimally damaging, light irradiation can be used to trigger specific surface morpho-physical properties in the presence of living cells. The interaction of light with an azopolymer film induces a mass migration phenomenon, allowing a variety of topographic patterns to be embossed on the polymeric film. Photoisomerization induces conformational changes at the molecular and macroscopic scale, resulting in light-induced variations of substrate morphological, physical, and mechanical properties. In this review, we discuss the photoactuation of azopolymeric interfaces to provide guidelines for the engineering and design of azopolymer films. Laser micropatterning for the modulation of azopolymer surfaces is examined as a way to diversify the capabilities of these polymers in cellular systems. Mass migration effects induced by azopolymer switching provides a foundation for performing a broad range of cellular manipulation techniques. Applications of azopolymers are explored in the context of dynamic culture systems, gaining insight into the complex processes involved in dynamic cell-material interactions. The review highlights azopolymers as a candidate for various applications in cellular control, including cell alignment, migration, gene expression, and others. Recent advances have underlined the importance of these systems in applications regarding three-dimensional cell culture and stem cell morphology. Azopolymers can be used not only to manipulate cells but also to probe for mechanistic studies of cellular crosstalk in response to chemical and mechanical stimuli.

Biosensing systems based on microneedles can overcome the stratum corneum of the skin, i. e. the outer natural barrier of the human body, without any pain and detect the target analytes directly in the interstitial fluid. Moreover, microneedle-based devices (MNDs) can combine diagnostic sensing and therapeutic administration of drugs in one single tool. From this point of view, more than a painless door to the human body, a MND represents the a perfect example of theranostic instrument, since a single device could quantify the real value of a relevant biomolecule, such as glucose, and accurately deliver a drug, the insulin, if needed. MNDs could be integrated on printed circuit boards, flexible electronics and microfluidic channels, thus allowing a continuous monitoring of the physiological parameters with very low invasiveness, together with sustained and localized administration of drugs. MNDs can be designed for very specific applications, from the detection of skin cancer to the monitoring of metabolic pathways. Moreover, several fabrication approaches have been introduced, from laboratories to large-scale production. Finally MNDs can be properly functionalized to enhance analytical performances.