3D Printing Technology: Role in Safeguarding Food Security

Abstract

The rising threats to food security include several factors, such as population growth, low agricultural investment, and poor distribution systems. Consequently, food insecurity results from a confluence of issues, including diseases, processing limitations, and distribution deficiencies. Food insecurity usually occurs in vulnerable areas where certain technologies and traditional food safety testing are not a viable solution for foodborne disease detection. In this regard, 3D printing technologies and 3D printed sensors open the platform to produce portable, accurate, and low-cost sensors that address the gaps and challenges in food security. In this paper, we discuss the perspective role of 3D printed sensors in food security in terms of food safety and food quality monitoring to provide reliable access to nutritious, affordable food. In each section, we highlight the advantages of 3D printing technology in terms of cost-effectiveness, accuracy, accessibility, and reproducibility compared to traditional manufacturing methodologies. Recent developments in robotic technologies for mechanization, such as food handling with soft grippers, are also discussed. Lastly, we delve into the applications of advanced 3D printing technologies in agricultural monitoring, particularly the future of plant wearables, environmental sensing, and overall plant health monitoring.

The term food security has evolved in its meaning throughout the years. In 2020, the United Nations Food and Agriculture Organization (FAO) broadened its definition to the physical, social, and economic access to food tied to health and socio-economic impact of COVID-19.¹ Food security is not limited to the quantity but also includes having access to safe and nutritious food with respect to cultural taste and dietary requirements while considering the factors of malnourishment.² According to the FAO, there are four elements that link the concept of food security: availability, access, utilization, and stability. If those are not satisfied, food insecurity occurs. In the rise of the industrialization era, food production has increased because of the feasibility of mass production using state-of-the-art technologies. It is a stepping stone toward more stable, sustainable food production by addressing the crisis caused by the population growth, low agricultural investment, and poor distribution systems.³ Also, due to advancements, food shelf life can be extended. Insect infestation has been a challenge to agricultural products since ancient times, but the formulation of pesticides and herbicides has aided pest management.⁴ However, in the process, hazardous contaminants and high-level preservatives were also introduced that impose threats for securing safe and nutritious food.⁵ Traditionally, analyzing food contaminants was performed in laboratories; however, such testing is time-consuming, requires trained personnel to evaluate the results, and is expensive.⁶⁻⁸ These conventional assessment methods are not suitable for the rapid, noninvasive, and convenient analysis used in the assessment of food safety. Recently, 3D printed sensors have demonstrated a potential in providing on-demand technology as it synthesized the production of low-cost, reliable, and accurate sensors.⁹ The presented advantages of 3D printing methodologies have drawn attention for utilization in a wide range of applications.

3D printed sensors and devices are seen in multiple key food sectors, such as agriculture,^10,11 water security,^12,13 food processing,^14,15 and food handling (Figure 1).¹⁶ The act of providing accurate and inexpensive technologies is needed to detect imminent threats in food security. Food insecurity usually occurs at vulnerable areas where traditional food safety testing is not a viable solution due to the lack of accessibility to certain technologies and high cost. This motivated an initiative to create a portable cost-effective device that can detect food safety threats to the most vulnerable communities in need of this technology. Aside from food insecurity, health risks from food contamination can also be identified. This technology is also utilized for identifying harmful toxic substances in water that result in contamination and cause disruptions to aquatic life and health issues. 3D printed sensors can also detect the spoilage of dairy products. In fact, one out of six people in the United States alone have gotten sick due to food borne diseases.¹⁷ The risk of food poisoning is initiated from fresh products such as meat, vegetable, fruit, and dairy products, and such contamination is occasionally not visible to the naked eye. Therefore, sensing capability like colorimetric indication in the packaging can help consumers use the product within its shelf life and decrease the incidents of food poisoning. That is where quality assessment tools and indicators are necessary to ensure food quality. Also, these technologies have a potential for scaling into industrial level food processing, such as implementing in food distribution and packaging, or devices for wide-scale agricultural land where the sensors can take part in crop picking and handling. The multifunctionality of the 3D printed devices promotes functional integration among autonomous systems.

Figure 1.

An overview of the applications of 3D printing technology in various food-related sectors. (From left to right and top to bottom) Adapted with permission from ref (66), Copyright 2017 MDPI, Basel, Switzerland; adapted with permission from ref (21), Copyright 2018 American Chemical Society; reproduced with permission from ref (94), Copyright 2017 Elsevier B.V.; and adapted with permission from ref (77), Copyright 2019 Wiley.

This Perspective discusses the role and potential of 3D printing technologies in safeguarding food security. There is an evident trend of favoring this state-of-the-art technology to be utilized in prototyping and manufacturing devices, sensors, actuators, and robotics.^18,19 Some of the advantages in using this technology boil down to its printing resolution, accuracy, reproducibility, speed, and accessibility in producing high-quality devices. In the succeeding sections, printed sensors used for food safety (detection of bacterial pathogens allergens and toxins), food preservation and monitoring of fresh products like vegetables and fruits,²⁰ monitoring meat²¹ and dairy²² products, and food processing are discussed. The integration of the 3D printed sensors on the Internet of Things (IoT) platform makes it more interesting as it expands the capability of the IoT sensors made from 3D printers for food security applications. Lastly, the paper discusses the role of 3D printed sensors in agricultural platforms, particularly the future of plant wearables and plant health monitoring. Different agricultural applications, including soil nutrient monitoring, soil moisture, gas monitoring, and electrophysiology of plants, are also considered. The need for agricultural technologies has arisen as the demand for food escalates with population growth. Moreover, these technologies are discussed later in the paper.

3D Printing Techniques in Fabricating Sensors and Actuators

Manufacturing sensors through 3D printing is growing in popularity. Recent works are drawn toward the capability of 3D printing technologies as it presents advantages compared to traditional manufacturing methodologies that were considered labor-intensive and costly. The 3D printing technologies used for the fabrication of environmental and agricultural sensors in ensuring food security are summarized in Table 1.

Table 1. 3D Printing Technologies and Their Applications.

3D printing technology		Device Type	Application	Material used in 3D printing	References
Extrusion Deposition processes	Fused Deposition Modeling (FDM)	Electrochemical sensors	Water pollutants sensor	Carbon-black loaded PLA	(34, 64, 65)
			Detection of mycotoxins	Graphene	(38)
			Pathogen detection	Carbon-loaded PLA	(56)
			Carcinogen detection	Graphene infused PLA	(57)
			Nitrite detection	Carbon-loaded PLA	(90)
		Soft grippers	Food handling	Polyeutherene	(76, 81−85)
		Plant wearables	Plant health detection	Conductive ink, ABS, TPU	(100−102)
		Microfluidic sensor	Soil nutrient detection	ABS and liquid reagents	(24)
			Milk adulteration	Resin	(68)
	Direct Ink Writing (DIW)	Electrochemical sensor	Wireless sensor for meat spoilage detector	Polyaniline	(94)
			H2O2 detection	Conductive ink	(46)
		Microfluidic sensor	Liquid food contaminants detector	Polymer materials	(69)
Photopolymerization processes	Stereolithography (SLA)	Microfluidic sensor	Detection of E. coli bacteria	Resin	(58)
			Allergen detection	Resin	(28)
		Electrochemical sensor	Wheat allergen detection	Methyl acryloyl gelatin	(43)
	PolyJet Printing	Surface plasmon resonance sensor	Water contaminant detection	VeroClear RGD810 and NOA88 resins	(33)
	Digital light projection (DLP)	Microfluidic separator devices	Detection of bacteria	Acrylate-based resin	(43)

The electrochemical sensors commonly used for food safety analysis are commonly produced using multiple-stage processing of combining chemicals and polymers as substrates.²³ Through 3D printing, a one-step fabrication process prepared through a multimaterial coprinting is utilized for manufacturing integrated sensors that require a high-level assembly between two or more materials. Similar advantages are reported for the fabrication of microfluidic devices and separation systems by 3D printing methods. These devices are commonly used for pathogenic detection and environmental monitoring. In particular, a microfluidic device used for monitoring soil nutrients is able to reduce manufacturing steps by utilizing a dual-nozzle fused deposition modeling (FDM) technique to provide both the sealing and liquid agents.²⁴ Likewise, the use of inkjet printing has benefitted the creation of biosensors for highly functional printed sensors used for food safety detection.²⁵ Compared to microcontact printing, sensors for detecting various contaminants produced by inkjet printers provide enhanced deposition control toward the quantity of enzymes precisely fabricated on the substrates.²⁶ Meanwhile, the contaminants in aqueous solutions can be detected through compact sensors that do not require clean-room-based fabrication for analysis. These devices include surface-enhanced Raman scattering (SERS)²⁷ and surface plasmon resonance (SPR) sensors.²⁸ Nowadays, SPR components are migrating from common fabrication methods such as laser-LIGA techniques²⁹ and silicone casting techniques.³⁰ Instead, the production of these sensors is performed using a 3D printing method to carry out the manufacturing of multiparameter sensors.³¹⁻³³ 3D printing is realized to be efficient in the production of devices in micrometer to nanoscale accuracy, which is suited for sophisticated fabrication of optical waveguide instruments for SPR application.³¹ Also, there is continuous development of compatible materials with 3D printers that can represent or exceed the certain standard composite for the fabrication of sensors. As an example, the glass used as standard material for an SPR system is substituted by silica glass³² and polymer optical fiber as these materials delivered an exceptional stability and mechanical performance comparable to the former. This accounts for the advantages of having rapid production and reproducibility compared to cast-based manufacturing, with cheaper production overhead as reported in recent works.³⁴ Another strength of 3D printing methodology is the capability to fabricate complex geometries from the designed materials which are impractical for traditional manufacturing methods to produce. Evidence of these merits is reflected in a food analysis application perspective with the 3D printed lattice architecture for SERS sensors. Although the proposed geometry is impractical for mold-based manufacturing, it is resolved by 3D printing. It is reported that the architectural geometry contributed to a higher sensitivity in terms of absorption behavior.³⁵ Another application for a designed 3D printed device is the soft grippers used for food processing.³⁶ Through 3D printing, architectural designs are employed to expand the functionalities and flexibility for food handling. The latest trend for soft grippers produced using FDM, or stereolithography (SLA), are embedded with sensing capabilities. This functionality is achieved through one-step fabrication with 3D printing technologies, which evolved to fulfill the requirements of rapid prototyping, reusability, or ease of swapping material between each printing.³⁷

3D Printed Sensors for Food Safety Purposes

In this section, 3D printed sensors for the detection of food safety are discussed. Sensors used for detecting food pathogens, insecticide concentration, and food allergens are illustrated in Figure 2. Food pathogens are produced because of bacterial activities, viruses, and contaminants found in the food or accumulated in the packaging after distribution. In addition, the use of unauthorized compounds and high-level pesticide residues are dangerous for human consumption. According to statistics, there are 2,643 cases in Asia, and up to 9,200,000 total cases of food borne diseases occur annually in the USA and in Europe.³⁸ These adverse effects of food globalization and immediate health safety threats drive the advancement of the quality of the sensors, which require rapid detection for the presence of preservatives,³⁹ pathogens,⁴⁰⁻⁴³ allergens,^28,44 insecticides,^45,46 and heavy metals⁴⁷ in food. One method for food testing is performed manually, such as observation, smell, and taste, but these assessments are prone to human error. There are more refined methods, such as infrared spectroscopy⁶ and nuclear magnetic resonance spectroscopy.⁷ However, these tests must be performed in the laboratory and by trained personnel. Through the advancement in bacteria testing, the strands of Escherichia coli (E. coli) are detected through noncultivating methods by impedance change in immunobiosensor chips characterized by atomic force microscopy.⁴⁸ The key point in producing such sensors points to producing a low-cost, effective device, regardless of the complexity of the shape or size of the sensor.⁴⁹ 3D printing expands the freedom of the producers to customize the function of the sensor into a compact design and optimize the space of the product while limiting the cost of production. Works detecting E. coli bacterial strand with an electrochemical biosensor claim to cost 2.50 USD per test unit compared to commercially available bacteria tests that are at least double its price at the date of writing.⁵⁰ On approach to realizing a series of functions in eliminating multiple step processing is by imagining a compact chamber to provide a solution to the bacterial separation issues by creating a microfluidic separation device, which is usually assembled using photolithography, but because of the complicated procedures associated with the common assembly method, later works seek to alleviate these challenges through 3D printing options.^51,52 Similarly, multistep fabrication to produce hydrogen peroxide (H₂O₂) sensors is demonstrated by inkjet printing.⁴⁷ This is versatile and highly sensitive to enzymatic reactions compared to commercially available sensors. It is printed with a conductive ink composed of biocompatible poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and enzymic, horseradish peroxidase (HRP) to produce an impedimetric-driven sensing mechanism. For applications where a rigid and bulky sensor is nonviable, a paper-based flexible sensor is presented. As digestion of high-concentration H₂O₂ may result in multiple health issues,⁵³ 3D printed flexible sensors have a potential practical application for the detection of food packaging.

Figure 2.

3D printed sensors are employed for detecting food pathogens, toxins, and allergens through various methods: (a) SLM-printed microfluidic intestinal microvilli for detecting the wheat allergen gliadin.⁴⁴ (b) FDM-printed tailored electrodes designed for carcinogen detection.⁵⁸ (c) FDM-printed graphene electrodes, along with their pretreatment, utilized for detecting mycotoxins in food.³⁹ (d) Using the DW method, the sensor detects hydrogen peroxide (H₂O₂) as a side product of enzymatic reactions.⁴⁷ (e) DLP-printed microfluidic magnetic preconcentrator for detecting bacterial pathogens.⁴³ (f) A 3D-printed microfluidic device for the detection of pathogenic bacteria.⁵⁹ (g) A portable FDM-printed pretreatment device for the detection of S. aureus, a food poisoning pathogen.⁵² (h) Microfluidic device designed for improved electrolysis.⁵¹ Reproduced with permission from ref (44), Copyright 2021 Elsevier B.V.; adapted from ref (58), Copyright 2022 MDPI, Basel, Switzerland; reproduced with permission from ref (39), Copyright 2020 Elsevier B.V.; reproduced with permission from ref (47), Copyright 2021 Wiley; reproduced with permission from ref (43), Copyright 2016 Elsevier B.V.; adapted from ref (59), Copyright 2015 Nature Publishing Group; reproduced with permission from ref (52), Copyright 2023 Elsevier B.V; adapted from ref (51), Copyright 2015 American Chemical Society.

3D printed conductive sensors have been shown to perform reliably for the electrochemical detection of water pollutants and contaminants.^54,55 3D printed electrochemical sensors are usually made from graphene or carbon-black induced polylactic acid (CB/PLA) materials. These materials are known to be sensitive toward chemical reactions induced from bacterial contamination and toxins⁵⁶ by producing electrical potential. A significant improvement from linear electrochemical response was observed from the 3D printed electrode with high detectability (limit of detection is 0.98 μmol L^–1).⁵⁷ Likewise, graphene strands are fused to synthesize an amperometric sensor that can detect the presence of carcinogen concentrations in palm oils using an amperometry detection method.⁵⁸ The promising performance of 3D printed electrochemical sensors toward detection of food pathogens indicates their huge potential in lightweight, inexpensive alternatives for portable assessment of food safety. Aside from electrochemical sensors, there are conductive sensors that assess food safety. In the recent development of functionalized microfluidic devices, a 3D printed separation delivers the production of an efficient device that performs facile detection of E. coli bacteria.⁵⁹ The utilization of a practical 3D-printed separation instrument enables the performance of liquid chromatography for detecting pathogenic bacteria. The clustered magnetic nanoparticles are separated within the device by utilizing force balance induced by Dean vortex flows, produced using the SLA printing method. As this technology continues to advance, it can enable swift on-site detection of pathogens. Beyond sensing capabilities, 3D printing offers the opportunity to fabricate additional structural components for analytical devices. A portable 3D printed chamber manufactured through an FDM technique is described to house the electrochemical components to perform multiple-pathogen identification^60,61 or specific bacteria screening for E. coli,⁵⁰S. aureus,⁵² cytotoxic food preservatives,⁶² and Bacillus cereus.⁴¹ Then, using a selective laser melting (SLM) printed compact microfluidic intestinal microvilli separator, it detects different concentrations of wheat allergen gliadin (range of 0.1–0.8 ng/mL).⁴⁴ Overall, the 3D printed sensors exhibited dependable and extensive sensitivity in identifying safety concerns such as the presence of microorganisms, pesticide residues, and contaminants through the recognition of enzymatic activity or voltametric response. These studies highlight the significant potential for 3D printed sensors in ensuring food safety and detecting pathogens.

3D Printed Sensors for Food Quality Monitoring and Control

The dynamics of 3D printing technologies promises a wide range of applications for monitoring food quality. Traditional analysis based on laboratory testing and rigid sensors is unsuited to meet the need for fast-paced, modern, and convenient food analysis. Rapid food quality assessment and monitoring based on 3D printing technologies will undertake an important role in households, water facilities, and manufacturing platforms. In food quality monitoring, fresh foods like poultry, meat, aquatic products, fruits, and vegetables require less preservation and processing (Figure 3). Shelving and distributing these products require careful consideration because microbial cultivation and browning processes are possible in environments where the processing and preparation involves water and exposure to oxygen, making fresh foods have a shorter shelf life and degraded nutritional content. Moreover, due to environmental factors like gases, humidity, and microorganisms, the quality of fresh food decreases throughout the entire process from harvest to consumption, which imposes financial losses and raises certain safety risks to customers. There are many intelligent detection technologies for monitoring the quality of the fresh food that can be produced using 3D printing technologies.^63,64 The advantage of 3D printed sensors over commercially available ones is their low cost and time-saving attributes, requiring no specialized knowledge. Also, some of these sensors offer noninvasive assessments that do not compromise food quality.

Figure 3.

Application of 3D printed sensors in food safety assessment is diverse, encompassing various functionalities: (a) A 3D printed pH sensor designed for the rapid detection of water contaminants.⁶⁶ (b) An integrated electrochemical cell, 3D-printed for the purpose of detecting Hg(II) up to 0.52 μg L^–1 in water.⁶⁷ (c) Designed nanocomposite lattices, coated with plasmonic nanoparticles, utilized for the detection of water pollutants.³⁵ (d) A nanostructured conductive polymer-based gas sensor, printed using inkjet technology, for the detection of meat spoilage, accompanied by smartphone notifications.²¹ (e) A 3D printed color-changing biosensor, enabling real-time contamination detection in food packaging.⁶⁸ (f) A 3D printed optofluidic microviscometer designed to determine milk adulteration.⁶⁹ (g) A 3D printed nanocellulose-based sensor tailored for monitoring and preserving the freshness of vegetables and fruits.²⁰ (h) A 3D printed RF wireless sensor developed for the monitoring of liquid food quality.⁷⁰ Adapted from ref (66), Copyright 2017 MDPI, Basel, Switzerland; reproduced with permission from ref (67), Copyright 2020 Elsevier B.V.; adapted from ref (35), Copyright 2023 Wiley; adapted from ref (21), Copyright 2018 American Chemical Society; adapted from ref (68), Copyright 2018 American Chemical Society; reproduced with permission from ref (69), Copyright 2016 IEEE; reproduced with permission from ref (20), Copyright 2015 Elsevier B.V.; adapted from ref (70), Copyright 2015 Nature Publishing Group.

Standards and methods for determining food quality rely on intrinsic attributes. Assessing food quality often involves pH variation testing and gas monitoring. Electrochemical sensors are utilized to analyze pH changes in water. 3D-printed carbon composites are prototyped as electrochemical sensors to detect pollutants in water.^65,66 The activated nanocarbon influences the voltammogram reading based on different pH variation. These sensors are manufactured by conductive polymer-based sensors by combination of direct ink writing (DIW) and FDM,⁶⁶ or FDM alone.^35,67 The implementation of 3D printed pH sensors demonstrates promising results with excellent conductivity response in different pH concentrations ranging from 6.4 to 9. However, further improvements for temperature correction must be addressed to compete with commercially available sensors.⁶⁶ Nonetheless, it demonstrates the potential in water quality indicators and implementation of pH sensors integrated with food packaging. Besides pH sensors, gas sensors are useful in performing microenvironment monitoring in foods. The wireless nanostructured conductive polymer-based gas sensor gives information on the biogenic amines produced by raw meat. With its high sensitivity characteristics, it is also used for switching an NFC tag that sends information to a mobile application indicating the status of the meat.²¹ Moreover, the sensor proved to be an effective meat spoilage indicator, showing potential for small-scale (individual food packages) or large-scale application meant for export containers, or refrigerators for handling an automated fresh food monitoring. Similarly, the concept has been presented in a 3D printed color changing biosensor for real-time contamination detection of contamination inside food packaging.⁶⁸ Devices utilized for determining milk adulteration using a 3D printed optofluidic microviscometer have been reported. To provide information regarding the adulteration percentage, the milk samples flow in the SLA-printed microtubes governed by the Hagen–Poiseulle flow equation. By carefully examining the device through fluorescence microscope, the samples present a distinguished width in the 3D printed microviscometer unique to the adulteration amount present in the milk. This technology displays a huge potential in real-time rapid detection of milk adulteration as it presents a high classification accuracy of 95%.⁶⁹ It suggests a prospective toward its application in continuous monitoring, particularly when a portable microscope is channeled in the setup. On the other hand, a liquid food quality monitoring using an electrochemical sensor is presented. Using the FDM technique, a passive RLC circuitry is induced to produce a 3D printed smart cap. To measure the presence of contaminants in liquid foods, the change in dielectric constant crates a shift in the resonance frequency of the sensor as it deteriorates. The change is detected by the embedded wireless coupled reader.⁷⁰ The results confirmed a shift of 4.3% in frequency for a milk sample when left for 36 h, indicating the changes in its composition. The real-time wireless sensor application indicates a new class of food quality detector device that benefits from 3D printing technology.

Lastly, a 3D printed biosensor is reported to be embedded on fresh food packaging to indicate its edibility and help preserve the vegetable or fruit freshness. Interestingly, the sensor is produced by coaxial 3D printing, which are hardly utilized in food packaging sensors. Cellulose nanofibers are used for creating the shell of the fibers and are known to have a shear-thinning behavior and are biocompatible, making them suitable for the application.⁷¹ However, the material alone is not feasible for 3D printing because of its viscoelasticity property. To cope with this, a cross-link of sodium alginate and k-carrageenan is combined to develop a suitable printing ink.^72,73 The core fibers are composed of anthocyanins that are used for visual monitoring based on 1-methylcyclopropene (1-MCP). The 1-MCP is responsible for maintaining the fruit or vegetable freshness as it irreversibly binds ethylene receptors, which is the ripening agent of the fruit or vegetables.⁷⁴ Remarkably, the sensor demonstrates a significant decrease in spoilage progression and decomposition with the presence of a sensor inside the packaging, honing an effective preservation and indicator for vegetable and fruit freshness. This presents and opportunity to mitigate the impacts of contracting food-borne diseases from contaminated food. An additional noteworthy aspect is the development of a 3D printed, nonchemically assembled food preservation device. This innovation is crucial in transforming food and extending its shelf life while reducing potential health hazards associated with chemical preservatives. In addition, progressive works are performed to transform edible materials such as gelatin and polysaccharide as potential food sensors.^75,76 In summary, these opportunities presented by 3D printing technologies for fabricating sensors are recognized as an efficient and cost-effective alternative technique for monitoring food quality.

3D Printed Devices for Food Processing

In this section, 3D printed sensors developed for food processing are discussed. 3D printed devices including customized grippers or soft robots for food handling applications have been developed. Highly specialized and multifunctional 3D printing techniques have gained attention in manufacturing for grippers embedded with sensors and actuators using industrial robot arms and mechanical machines (Figure 4).⁷⁷ Fabricating soft grippers using 3D printing technology reduces the difficulty of creating temperature-stimulated grippers and enhances design flexibility through seamless incorporation of embedded force sensors.^78,79 The variety of robot gripper designs are characterized to possess the ability to elastically deform and alter their profile based on their function and external constraints. Generally, 3D printed grippers are demonstrated to have secure food-handling capability and a desgined structure with shape-retention memory or origami folded hinges with force sensors embedded in the fingertips.

Figure 4.

3D printed devices play a crucial role in various aspects of food processing. Here are some examples: (a) A soft gripper, crafted with FDM printing technology and integrated into a three-degree-of-freedom robot for delicate food handling.⁷⁷ (b) A comprehensive system of 3D printed sensors and devices is applied to facilitate efficient food sorting processes.⁸² (c) 3D origami sensing devices contribute to enhanced capabilities in food processing.⁸⁴ (d) Soft robotic grippers envision a nondestructive sorting approach, ensuring handling in the food processing workflow.⁸⁵ (e) Specialized grippers are assembled to grasp shredded food, streamlining the processing of such items.⁸³ (f) A 3D-printed neuromorphic humanoid hand is designed for the purpose of grasping unknown objects, showcasing adaptability in the food processing domain.⁸⁶ Adapted from ref (77), Copyright 2019 Wiley; reproduced with permission from ref (82), Copyright 2021 IEEE; reproduced with permission from ref (84), Copyright 2021 Wiley; adapted from ref (85), Copyright 2022 American Chemical Society; reproduced with permission from ref (83), Copyright 2019 IEEE; reproduced with permission from ref (86), Copyright 2022 Elsevier B.V.

One challenge in attaining food handling capability is the limited applicability of grippers with fixed finger placement, hindering their ability to handle complex processes.^80,81 Soft grippers fabricated with FDM printing technology mounted in a three degree-of-freedom robot were demonstrated for the handling of food. Different gripping stance and bending angles were adopted based on the constituted shape and size of the food sample. To mitigate overbending, a reconfigurable gripper technique is devised to handle delicate food samples such as tofu, noodles, long beans, or pudding. Also, the 3D printed actuator is programed to provide an optimized robot path for enhanced gripping performance.⁸² A lightweight architectural body compliant robotic gripper has been explored to investigate the application of cellular architecture in composing a repeatable and reliable gripper motion.⁸³ Recently, nontrivial dimension sorting based on soft robotic grippers has been proposed to perform a nondestructive sorting method.^84,85 The material used for the aforementioned configuration is usually polyurethane (thermoplastic),⁷⁷ or silicon rubber,⁸⁴ due to its high stiffness and viscoelastic nature. The potential role of 3D printing provides an expanded degree of fabrication freedom that permits the creation of tailored grippers embedded with sensors for advancing specific applications.⁸⁶ Through the integration of automating techniques, the soft grippers may take a big part in industry 4.0 platforms for food processing, handling, and packaging. These studies presented the current challenges and forecast an increase in demand for these technologies in the future.

3D Printed Sensors and Devices in Agriculture

Recently, the emergence of 3D printing technologies has expanded the versatility of sensors used in agriculture. Agriculture is a major dynamic component for providing food security. This section discusses the perspective role of 3D printed sensors in the agricultural sector toward building thriving, advanced sustainable farming. Sensors are an essential key technology in executing smart farming practices in the field or in a more controlled environment like greenhouses. With sensors, the monitoring of vital information like plant growth, soil (e.g., moisture, and nutrient), and environmental conditions is possible. Recent innovative instruments have been introduced to build a nondestructive monitoring system to acquire data without interfering with environmental factors or the crop itself. One of the critical coefficients associated with plant growth is the soil moisture content. The amount of water concentration in soil provides an insight for the correlation between soil moisture and plant health. Scarcity of water in plants could lead to wilting, stunted growth, and poor yield. For monitoring, 3D printed sensors are favored due to the ease of fabrication, as in the works in which a wireless split-ring resonator is introduced and used for precise and noninvasive soil moisture monitoring (Figure 5).⁸⁷ Likewise, an RFID-enabled sensor utilized the sensitivity between the inkjet-printed dielectric materials, which varies the transmitted power produced depending on the moisture detected.⁸⁸ An IoT-enabled sensor with a dedicated unit for measuring soil moisture is characterized to be fully 3D printed. The stand-alone device gathers data with 0.7 μs sampling time and because of the IoT integration, the data transmission from the field to the farmers is more efficient. However, the drawback for this device is its power limitations caused by it being powered by a battery.⁸⁹ Aside from moisture, the nutrients in the soil are also critical to be monitored. The information on soil nutrients allows the farmers to allocate resources and fertilize the soil before agricultural activity. However, an excess application of fertilizer increases nitrate concentration that leads to potential pollution of water resources.⁹⁰ A 3D printed microfluidic device is devised to detect within the normal range of 0–60 ppm concentration of nitrate in soil.²⁴ Similarly, nitrite detection is performed with a miniaturized electrochemical sensor fabricated using the FDM technique.⁹¹ On another note, an interdigitated electrode is 3D printed to create an electronic tongue (e-tongue). An e-tongue mimics the human sensory functionalities and has the functionality to detect nutrients (N, P, K, etc.) in soil.^92,93 The use of 3D printing techniques for fabrication assisted in achieving outstanding reproducibility for the sensors, in which the deviation ranges within 1 pF for 10 printed sensors.⁹²

Figure 5.

3D printed sensors play a pivotal role in soil moisture detection and soil nutrient detection. Here are notable examples: (a) A 3D printed microwave antenna is utilized as a sensor to detect soil water content.⁸⁷ (b) An RFID-enabled inkjet-printed soil moisture sensor enhances precision in moisture detection.⁸⁸ (c) Dedicated 3D printed sensor elements are designed for measuring and communicating with IoT-enabled monitoring of soil moisture.⁸⁹ (d) Microfluidic sensors, printed using the FDM technique, are utilized for determining nitrite concentration in soil.²⁴ (e) A 3D printed IoT-enabled ion concentration detector using S₁₁.¹⁰² (f) A miniaturized nitrite detection device created through 3D printing.⁹¹ (g) 3D printed synaptic sensor for soil nutrient concentration detection.¹¹² Adapted from ref (87), Copyright 2020 MDPI, Basel, Switzerland; reproduced with permission from ref (88), Copyright 2014 IEEE; adapted from ref (89), Copyright 2020 MDPI, Basel, Switzerland; adapted from ref (24), Copyright 2017 American Chemical Society; and reproduced with permission from 102, Copyright 2019 Wiley; with permission from ref (91), Copyright 2021 IEEE; and with permission from ref (112), Copyright 2017 Wiley.

The electrophysiology of a plant refers to the electronic pulses it produces in response to stimuli from the environment or its physical body, and these signals can be correlated with the plant’s health status. The electrophysiological signals from plants are detected using 3D-printed electrodes attached to the stomata of the plant. This setup accurately measures transpiration in sunflowers and corn using a heat-pulse method (Figure 6).⁹⁴ As an alternative, noninvasive devices are available to measure plant activity, such as microfabricated flexible sensors attached on the plant’s leaves. An electro-mechanical sensor for stomata monitoring is created to track the latency of single stomatal opening and closing time and to monitor long-term leaf physiology⁹⁵ and microclimate.⁹⁶

Figure 6.

3D printed sensors play a significant role in electrophysiology sensing of plants, measuring the potential difference of the plant with respect to the ground, and other sensors for agricultural purposes. Notable examples include the following: (a) 3D-printed sensor bodies accurately measure transpiration in sunflowers and corn using the heat-pulse method.⁹⁴ (b) An electro-mechanical sensor of stomata is created for tracking the latency of single stomatal opening and closing times.⁹⁶ (c) A 3D printed plant wearable is developed for monitoring leaf physiology and microclimate.⁹⁵ (d) Multimodal plant healthcare flexible sensor system using inkjet-printed silver nanoparticles.¹⁰¹ (e) Compact device for sensing environmental temperature, humidity, and H₂S levels.¹¹⁰ (f) 3D printed flexible plant wearable for monitoring humidity and temperature.¹⁰³ Reproduced with permission from ref (94), Copyright 2017 Elsevier B.V.; reproduced with permission from ref (96), Copyright 2017 The Royal Society of Chemistry; adapted from ref (95), Copyright 2019 American Chemical Society; adapted from ref (101), Copyright 2020 American Chemical Society; reproduced with permission from ref (110), Copyright 2019 Wiley; adapted from ref (103), Copyright 2018 Nature Publishing Group.

We need to also consider the biogas byproducts emitted from producing agricultural products. For example, ammonia plays a crucial role in plant development due to its nitrogen content, a core element in chlorophyll production in plants.⁹⁷ However, the substantial volume of ammonia emissions contributes to particulate matter (PM2.5), resulting in biodiversity loss among plant ecosystems and adverse effects on human health.⁹⁸ Traditional rigid gas sensors for detecting ammonia, a colorless and toxic gas, are typically bulky, are complex to manufacture, and require operation at high temperatures, limiting their applications and hindering integration with other gas sensors. Recent advancements include an improved 3D printed ammonia sensor designed to operate at room temperature. Fabricated through inkjet printing, this sensor offers controlled film thickness, simplicity, and cost-effectiveness compared to traditional methods. Utilizing a combination of FeCl₃ and PEDOT:PSS materials, the sensor exhibits mechanical flexibility, tunability, and the ability to be processed with high throughput at low temperatures. These qualities make it a potential candidate for applications in plant wearables.^99,100 Recent work regarding plant wearables involves a multimodal plant healthcare flexible sensor system that was developed using inkjet-printed silver nanoparticles.¹⁰¹ This compact device wirelessly senses temperature, humidity, and hydrogen sulfide levels—critical environmental indicators for conditions such as forest fires and industrial leaks.¹⁰² Additionally, a 3D printed flexible wearable plant monitoring circuit aims to record ambient temperature and humidity.¹⁰³

Lastly, gas sensors are playing a vital role in providing information about crop status or prevailing environmental factors that can affect plant health (Figure 7).^104,105 In detecting gas for agricultural application, one of the common variables being observed is SnO₂. This is a compound reactive to oxidizing gases such as oxygen that produces an oxidation–reduction reaction through the film surface. The resistance change from the electrochemical SnO₂ comes from the depletion layer built up from the electron–gas molecule bonding from the conduction band. Relatively, when oxygen molecules are bonded, the resistance increases, while an opposite response is observed when concentrations of ethanol, ammonia, or carbon monoxide gases are detected. Recently, flexible sensors for SnO₂ monitoring have been produced through 3D printing. By employing printing methods in sensor development, these sensors demonstrated the ability to endure elevated temperatures. This stands as a notable advantage when compared to the conventional silicon-based gas sensors.¹⁰⁶ On the other hand, temperature and humidity are crucial physical quantities that directly influence plant growth and health. Humidity is perceived as the moisture variation associated with regulation of water loss particularly in cuticular and stomatal portions of the plant.¹⁰⁷ In addition, 3D printed humidity sensors have been created using inkjet printing,¹⁰⁸ such as an extremely sensitive all-graphene humidity sensor produced through laser direct writing and a flexible printed sensor designed to detect toluene content and relative humidity.¹⁰⁹

Figure 7.

3D printed sensors for gas monitoring and humidity sensing. (a) A 3D printed ammonia gas sensor prepared through inkjet printing.⁹⁹ (b) Multiple gas sensor that reacts with ethanol, ammonia, and carbon monoxide.¹⁰⁶ (c) A gas indicator printed using DLP, measuring ammonia levels.¹⁰⁰ (d) Encapsulated humidity and temperature sensors, printed using inkjet technology.¹⁰⁸ (e) A highly sensitive graphene-based humidity sensor, manufactured through laser direct writing.¹⁰⁹ (f) Flexible 3D-printed sensors designed to detect toluene content and relative humidity.¹¹¹ Reproduced with permission from ref (99), Copyright 2019 Elsevier B.V.; reproduced with permission from ref (106), Copyright 2019 The Royal Society of Chemistry; reproduced with permission from ref (100), Copyright 2020 Elsevier B.V.; reproduced with permission from ref (108), Copyright 2013 IOP Publishing Ltd.; adapted from ref (109), Copyright 2018 American Chemical Society; reproduced with permission from ref (111), Copyright 2015 Elsevier B.V.

Perspective

3D printing stands at the forefront of transformative fabrication methodologies for the creation of sensors, actuators, and devices. The discussion concentrated on two key 3D printing technologies, extrusion deposition and photopolymerization processes, which provide an alternative manufacturing methodology to realize customizable and low-cost rapid production with a reduced fabrication phase. This paper explores the role of 3D printing technology in safeguarding food security in terms of applications for food safety, quality monitoring, food processing. Conceptualized 3D printed sensors and devices used for the agricultural sector are also covered. This paper established an overview of the significant benefits and challenges of 3D printing technology for real-world applications, therefore providing an insight into the future perspectives on this technology.

The trends toward favoring 3D printing manufacturing over traditional sensor fabrication methods are evident due its advantages. The simplicity of multimaterial printing addresses challenges in integrated sensor fabrication, particularly in the production of electrochemical sensors crucial for highly functional printed sensors deployed in food safety and quality monitoring. We have seen multimaterial 3D printing overcome the impediments in producing microfluidic devices. The typical manufacturing approach relies on mold-based methods, which degrade over time and are impractical for large-volume production. The adaptability of 3D printing technology to print complex shapes and geometries has paved the way for the development of devices for detecting bacterial pathogens and toxins. Furthermore, the continuous development for high-resolution fabrication in 3D printing technologies makes it suitable for manufacturing microfluidic devices and separation systems. Lastly, the cost-effectiveness of 3D printing manufacturing takes into account the reproducibility, operational cost, machine cost, and materials.

Meanwhile, the continuous development in material science is a critical factor for overcoming the challenges in printing devices using 3D printing technology. Synthesizing materials with reinforced components is necessary to produce reliable materials suitable for printing. Besides, the material construction assumes the promising perspective to be an alternative to the standard fabrication materials for developing multifunctional sensors and devices with comparable or enhanced performance. Therefore, breakthrough materials should continue to be developed with an eye toward creating low-cost, effective, and highly reliable materials to support the practical applications of 3D printing technology.

Moving forward to the integrated use of 3D printing technology, it is poised to revolutionize not only food safety assessments, quality monitoring, and processing but also the broader landscape of intelligent farming and processing. The synergy between 3D printed devices, artificial intelligence, and Internet of Things (IoT) technology introduces intelligent opportunities for smart processing and farming. The flexibility and customization offered by 3D printing sensors integrated into systems exhibit limitless potential across various fields, promising enhancements in every aspect of food security. As challenges in large-scale manufacturing using 3D printing technologies are systematically addressed, there is an expanding path toward future applications and innovations that focus on food production and security.

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

The authors declare no competing financial interest.